badvpn/server/server.c

/**
 * @file server.c
 * @author Ambroz Bizjak <ambrop7@gmail.com>
 * 
 * @section LICENSE
 * 
 * This file is part of BadVPN.
 * 
 * BadVPN is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 * 
 * BadVPN is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/*
 NOTE:
 This program works with I/O inside the BPending job environment.
 A consequence of this is that in response to an input, we can't
 directly do any output, but instead have to schedule outputs.
 Because all the buffers used (e.g. client control buffers and peer flows)
 are based on flow components, it is impossible to directly write two or more
 packets to a buffer.
 To, for instance, send two packets to a buffer, we have to first schedule
 writing the second packet (using BPending), then send the first one.
*/

#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include <stdarg.h>

// NSPR and NSS
#include <prinit.h>
#include <prio.h>
#include <prerror.h>
#include <prtypes.h>
#include <nss.h>
#include <ssl.h>
#include <cert.h>
#include <keyhi.h>
#include <secasn1.h>

// BadVPN
#include <misc/version.h>
#include <misc/debug.h>
#include <misc/offset.h>
#include <misc/nsskey.h>
#include <misc/byteorder.h>
#include <misc/loglevel.h>
#include <misc/loggers_string.h>
#include <predicate/BPredicate.h>
#include <base/BLog.h>
#include <system/BSignal.h>
#include <system/BTime.h>
#include <base/DebugObject.h>
#include <system/BAddr.h>
#include <system/Listener.h>
#include <security/BRandom.h>
#include <nspr_support/DummyPRFileDesc.h>

#ifndef BADVPN_USE_WINAPI
#include <system/BLog_syslog.h>
#endif

#include <server/server.h>

#include <generated/blog_channel_server.h>

#define COMPONENT_SOURCE 1
#define COMPONENT_SINK 2
#define COMPONENT_DECODER 3

#define LOGGER_STDOUT 1
#define LOGGER_SYSLOG 2

// parsed command-line options
struct {
    int help;
    int version;
    int logger;
    #ifndef BADVPN_USE_WINAPI
    char *logger_syslog_facility;
    char *logger_syslog_ident;
    #endif
    int loglevel;
    int loglevels[BLOG_NUM_CHANNELS];
    int ssl;
    char *nssdb;
    char *server_cert_name;
    char *listen_addrs[MAX_LISTEN_ADDRS];
    int num_listen_addrs;
    char *comm_predicate;
    char *relay_predicate;
} options;

// listen addresses
BAddr listen_addrs[MAX_LISTEN_ADDRS];
int num_listen_addrs;

// communication predicate
BPredicate comm_predicate;

// communication predicate functions
BPredicateFunction comm_predicate_func_p1name;
BPredicateFunction comm_predicate_func_p2name;
BPredicateFunction comm_predicate_func_p1addr;
BPredicateFunction comm_predicate_func_p2addr;

// variables when evaluating the predicate, adjusted before every evaluation
const char *comm_predicate_p1name;
const char *comm_predicate_p2name;
BIPAddr comm_predicate_p1addr;
BIPAddr comm_predicate_p2addr;

// relay predicate
BPredicate relay_predicate;

// gateway predicate functions
BPredicateFunction relay_predicate_func_pname;
BPredicateFunction relay_predicate_func_rname;
BPredicateFunction relay_predicate_func_paddr;
BPredicateFunction relay_predicate_func_raddr;

// variables when evaluating the comm_predicate, adjusted before every evaluation
const char *relay_predicate_pname;
const char *relay_predicate_rname;
BIPAddr relay_predicate_paddr;
BIPAddr relay_predicate_raddr;

// i/o system
BReactor ss;

// server certificate if using SSL
CERTCertificate *server_cert;

// server private key if using SSL
SECKEYPrivateKey *server_key;

// model NSPR file descriptor to speed up client initialization
PRFileDesc model_dprfd;
PRFileDesc *model_prfd;

// listeners
Listener listeners[MAX_LISTEN_ADDRS];
int num_listeners;

// number of connected clients
int clients_num;

// ID assigned to last connected client
peerid_t clients_nextid;

// clients list
LinkedList2 clients;

// clients tree (by ID)
BAVL clients_tree;

// cleans everything up that can be cleaned in order to return
// from the event loop and exit
static void terminate (void);

// prints help text to standard output
static void print_help (const char *name);

// prints program name and version to standard output
static void print_version (void);

// parses the command line
static int parse_arguments (int argc, char *argv[]);

// processes certain command line options
static int process_arguments (void);

// handler for program termination request
static void signal_handler (void *unused);

// listener socket handler, accepts new clients
static void listener_handler (Listener *listener);

// adds a client. The client structure must have the sock and addr members
// already initialized.
static void client_add (struct client_data *client);

// removes a client
static void client_remove (struct client_data *client);

// job for notifying clients when a client is removed
static void client_dying_job (struct client_data *client);

// frees resources used by a client
static void client_dealloc (struct client_data *client);

// passes a message to the logger, prepending about the client
static void client_log (struct client_data *client, int level, const char *fmt, ...);

// client activity timer handler. Removes the client.
static void client_disconnect_timer_handler (struct client_data *client);

// drives cline SSL handshake
static void client_try_handshake (struct client_data *client);

// event handler for driving client SSL handshake
static void client_handshake_read_handler (struct client_data *client, PRInt16 event);

// initializes the I/O porition of the client
static int client_init_io (struct client_data *client);

// deallocates the I/O portion of the client. Must have no outgoing flows.
static void client_dealloc_io (struct client_data *client);

// handler for client I/O errors. Removes the client.
static void client_error_handler (struct client_data *client, int component, int code);

// provides a buffer for sending a control packet to the client
static int client_start_control_packet (struct client_data *client, void **data, int len);

// submits a packet written after client_start_control_packet
static void client_end_control_packet (struct client_data *client, uint8_t id);

// sends a newclient message to a client
static int client_send_newclient (struct client_data *client, struct client_data *nc, int relay_server, int relay_client);

// sends an endclient message to a client
static int client_send_endclient (struct client_data *client, peerid_t end_id);

// handler for packets received from the client
static void client_input_handler_send (struct client_data *client, uint8_t *data, int data_len);

// processes hello packets from clients
static void process_packet_hello (struct client_data *client, uint8_t *data, int data_len);

// processes outmsg packets from clients
static void process_packet_outmsg (struct client_data *client, uint8_t *data, int data_len);

// creates a peer flow
static struct peer_flow * peer_flow_create (struct client_data *src_client, struct client_data *dest_client);

// deallocates a peer flow
static void peer_flow_dealloc (struct peer_flow *flow);

// disconnects the source client from a peer flow
static void peer_flow_disconnect (struct peer_flow *flow);

// provides a buffer for sending a peer-to-peer packet
static int peer_flow_start_packet (struct peer_flow *flow, void **data, int len);

// submits a peer-to-peer packet written after peer_flow_start_packet
static void peer_flow_end_packet (struct peer_flow *flow, uint8_t type);

// handler called by the queue when a peer flow can be freed after its source has gone away
static void peer_flow_handler_canremove (struct peer_flow *flow);

// generates a client ID to be used for a newly connected client
static peerid_t new_client_id (void);

// finds a client by its ID
static struct client_data * find_client_by_id (peerid_t id);

// checks if two clients are allowed to communicate. May depend on the order
// of the clients.
static int clients_allowed (struct client_data *client1, struct client_data *client2);

// communication predicate function p1name
static int comm_predicate_func_p1name_cb (void *user, void **args);

// communication predicate function p2name
static int comm_predicate_func_p2name_cb (void *user, void **args);

// communication predicate function p1addr
static int comm_predicate_func_p1addr_cb (void *user, void **args);

// communication predicate function p2addr
static int comm_predicate_func_p2addr_cb (void *user, void **args);

// checks if relay is allowed for a client through another client
static int relay_allowed (struct client_data *client, struct client_data *relay);

// relay predicate function pname
static int relay_predicate_func_pname_cb (void *user, void **args);

// relay predicate function rname
static int relay_predicate_func_rname_cb (void *user, void **args);

// relay predicate function paddr
static int relay_predicate_func_paddr_cb (void *user, void **args);

// relay predicate function raddr
static int relay_predicate_func_raddr_cb (void *user, void **args);

// comparator for peerid_t used in AVL tree
static int peerid_comparator (void *unused, peerid_t *p1, peerid_t *p2);

static int create_know (struct client_data *from, struct client_data *to, int relay_server, int relay_client);
static void remove_know (struct peer_know *k);
static void know_inform_job_handler (struct peer_know *k);
static void uninform_know (struct peer_know *k);
static void know_uninform_job_handler (struct peer_know *k);

int main (int argc, char *argv[])
{
    if (argc <= 0) {
        return 1;
    }
    
    // parse command-line arguments
    if (!parse_arguments(argc, argv)) {
        fprintf(stderr, "Failed to parse arguments\n");
        print_help(argv[0]);
        goto fail0;
    }
    
    // handle --help and --version
    if (options.help) {
        print_version();
        print_help(argv[0]);
        return 0;
    }
    if (options.version) {
        print_version();
        return 0;
    }
    
    // initialize logger
    switch (options.logger) {
        case LOGGER_STDOUT:
            BLog_InitStdout();
            break;
        #ifndef BADVPN_USE_WINAPI
        case LOGGER_SYSLOG:
            if (!BLog_InitSyslog(options.logger_syslog_ident, options.logger_syslog_facility)) {
                fprintf(stderr, "Failed to initialize syslog logger\n");
                goto fail0;
            }
            break;
        #endif
        default:
            ASSERT(0);
    }
    
    // configure logger channels
    for (int i = 0; i < BLOG_NUM_CHANNELS; i++) {
        if (options.loglevels[i] >= 0) {
            BLog_SetChannelLoglevel(i, options.loglevels[i]);
        }
        else if (options.loglevel >= 0) {
            BLog_SetChannelLoglevel(i, options.loglevel);
        }
    }
    
    BLog(BLOG_NOTICE, "initializing "GLOBAL_PRODUCT_NAME" "PROGRAM_NAME" "GLOBAL_VERSION);
    
    // initialize sockets
    if (BSocket_GlobalInit() < 0) {
        BLog(BLOG_ERROR, "BSocket_GlobalInit failed");
        goto fail1;
    }
    
    // process arguments
    if (!process_arguments()) {
        BLog(BLOG_ERROR, "Failed to process arguments");
        goto fail1;
    }
    
    // init communication predicate
    if (options.comm_predicate) {
        // init predicate
        if (!BPredicate_Init(&comm_predicate, options.comm_predicate)) {
            BLog(BLOG_ERROR, "BPredicate_Init failed");
            goto fail1;
        }
        
        // init functions
        BPredicateFunction_Init(&comm_predicate_func_p1name, &comm_predicate, "p1name", (int []){PREDICATE_TYPE_STRING}, 1, comm_predicate_func_p1name_cb, NULL);
        BPredicateFunction_Init(&comm_predicate_func_p2name, &comm_predicate, "p2name", (int []){PREDICATE_TYPE_STRING}, 1, comm_predicate_func_p2name_cb, NULL);
        BPredicateFunction_Init(&comm_predicate_func_p1addr, &comm_predicate, "p1addr", (int []){PREDICATE_TYPE_STRING}, 1, comm_predicate_func_p1addr_cb, NULL);
        BPredicateFunction_Init(&comm_predicate_func_p2addr, &comm_predicate, "p2addr", (int []){PREDICATE_TYPE_STRING}, 1, comm_predicate_func_p2addr_cb, NULL);
    }
    
    // init relay predicate
    if (options.relay_predicate) {
        // init predicate
        if (!BPredicate_Init(&relay_predicate, options.relay_predicate)) {
            BLog(BLOG_ERROR, "BPredicate_Init failed");
            goto fail1_1;
        }
        
        // init functions
        BPredicateFunction_Init(&relay_predicate_func_pname, &relay_predicate, "pname", (int []){PREDICATE_TYPE_STRING}, 1, relay_predicate_func_pname_cb, NULL);
        BPredicateFunction_Init(&relay_predicate_func_rname, &relay_predicate, "rname", (int []){PREDICATE_TYPE_STRING}, 1, relay_predicate_func_rname_cb, NULL);
        BPredicateFunction_Init(&relay_predicate_func_paddr, &relay_predicate, "paddr", (int []){PREDICATE_TYPE_STRING}, 1, relay_predicate_func_paddr_cb, NULL);
        BPredicateFunction_Init(&relay_predicate_func_raddr, &relay_predicate, "raddr", (int []){PREDICATE_TYPE_STRING}, 1, relay_predicate_func_raddr_cb, NULL);
    }
    
    // init time
    BTime_Init();
    
    // initialize reactor
    if (!BReactor_Init(&ss)) {
        BLog(BLOG_ERROR, "BReactor_Init failed");
        goto fail2;
    }
    
    // setup signal handler
    if (!BSignal_Init(&ss, signal_handler, NULL)) {
        BLog(BLOG_ERROR, "BSignal_Init failed");
        goto fail2a;
    }
    
    if (options.ssl) {
        // initialize NSPR
        PR_Init(PR_USER_THREAD, PR_PRIORITY_NORMAL, 0);
        
        // initialize i/o layer types
        if (!DummyPRFileDesc_GlobalInit()) {
            BLog(BLOG_ERROR, "DummyPRFileDesc_GlobalInit failed");
            goto fail3;
        }
        if (!BSocketPRFileDesc_GlobalInit()) {
            BLog(BLOG_ERROR, "BSocketPRFileDesc_GlobalInit failed");
            goto fail3;
        }
        
        // initialize NSS
        if (NSS_Init(options.nssdb) != SECSuccess) {
            BLog(BLOG_ERROR, "NSS_Init failed (%d)", (int)PR_GetError());
            goto fail3;
        }
        if (NSS_SetDomesticPolicy() != SECSuccess) {
            BLog(BLOG_ERROR, "NSS_SetDomesticPolicy failed (%d)", (int)PR_GetError());
            goto fail4;
        }
        
        // initialize server cache
        if (SSL_ConfigServerSessionIDCache(0, 0, 0, NULL) != SECSuccess) {
            BLog(BLOG_ERROR, "SSL_ConfigServerSessionIDCache failed (%d)", (int)PR_GetError());
            goto fail4;
        }
        
        // open server certificate and private key
        if (!open_nss_cert_and_key(options.server_cert_name, &server_cert, &server_key)) {
            BLog(BLOG_ERROR, "Cannot open certificate and key");
            goto fail4a;
        }
        
        // initialize model SSL fd
        DummyPRFileDesc_Create(&model_dprfd);
        if (!(model_prfd = SSL_ImportFD(NULL, &model_dprfd))) {
            BLog(BLOG_ERROR, "SSL_ImportFD failed");
            ASSERT_FORCE(PR_Close(&model_dprfd) == PR_SUCCESS)
            goto fail5;
        }
        
        // set server certificate
        if (SSL_ConfigSecureServer(model_prfd, server_cert, server_key, NSS_FindCertKEAType(server_cert)) != SECSuccess) {
            BLog(BLOG_ERROR, "SSL_ConfigSecureServer failed");
            goto fail6;
        }
    }
    
    // initialize number of clients
    clients_num = 0;
    
    // first client ID will be zero
    clients_nextid = 0;
    
    // initialize clients linked list
    LinkedList2_Init(&clients);
    
    // initialize clients tree
    BAVL_Init(&clients_tree, OFFSET_DIFF(struct client_data, id, tree_node), (BAVL_comparator)peerid_comparator, NULL);
    
    // initialize listeners
    num_listeners = 0;
    while (num_listeners < num_listen_addrs) {
        if (!Listener_Init(&listeners[num_listeners], &ss, listen_addrs[num_listeners], (Listener_handler)listener_handler, &listeners[num_listeners])) {
            BLog(BLOG_ERROR, "Listener_Init failed");
            goto fail7;
        }
        num_listeners++;
    }
    
    // enter event loop
    BLog(BLOG_NOTICE, "entering event loop");
    BReactor_Exec(&ss);
    
    // free clients
    LinkedList2Node *node;
    while (node = LinkedList2_GetFirst(&clients)) {
        struct client_data *client = UPPER_OBJECT(node, struct client_data, list_node);
        
        // remove outgoing knows
        LinkedList2Node *node2;
        while (node2 = LinkedList2_GetFirst(&client->know_out_list)) {
            struct peer_know *k = UPPER_OBJECT(node2, struct peer_know, from_node);
            remove_know(k);
        }
        
        // remove incoming knows
        LinkedList2Node *node3;
        while (node3 = LinkedList2_GetFirst(&client->know_in_list)) {
            struct peer_know *k = UPPER_OBJECT(node3, struct peer_know, to_node);
            remove_know(k);
        }
        
        // remove outgoing flows
        LinkedList2Node *flow_node;
        while (flow_node = LinkedList2_GetFirst(&client->peer_out_flows_list)) {
            struct peer_flow *flow = UPPER_OBJECT(flow_node, struct peer_flow, src_list_node);
            ASSERT(flow->src_client == client)
            
            // allow freeing queue flows at dest
            PacketPassFairQueue_PrepareFree(&flow->dest_client->output_peers_fairqueue);
            
            // deallocate flow
            peer_flow_dealloc(flow);
        }
        
        // deallocate client
        client_dealloc(client);
    }
fail7:
    while (num_listeners > 0) {
        num_listeners--;
        Listener_Free(&listeners[num_listeners]);
    }
    
    if (options.ssl) {
fail6:
        ASSERT_FORCE(PR_Close(model_prfd) == PR_SUCCESS)
fail5:
        CERT_DestroyCertificate(server_cert);
        SECKEY_DestroyPrivateKey(server_key);
fail4a:
        ASSERT_FORCE(SSL_ShutdownServerSessionIDCache() == SECSuccess)
fail4:
        ASSERT_FORCE(NSS_Shutdown() == SECSuccess)
fail3:
        ASSERT_FORCE(PR_Cleanup() == PR_SUCCESS)
        PL_ArenaFinish();
    }
    
    BSignal_Finish();
fail2a:
    BReactor_Free(&ss);
fail2:
    if (options.relay_predicate) {
        BPredicateFunction_Free(&relay_predicate_func_raddr);
        BPredicateFunction_Free(&relay_predicate_func_paddr);
        BPredicateFunction_Free(&relay_predicate_func_rname);
        BPredicateFunction_Free(&relay_predicate_func_pname);
        BPredicate_Free(&relay_predicate);
    }
fail1_1:
    if (options.comm_predicate) {
        BPredicateFunction_Free(&comm_predicate_func_p2addr);
        BPredicateFunction_Free(&comm_predicate_func_p1addr);
        BPredicateFunction_Free(&comm_predicate_func_p2name);
        BPredicateFunction_Free(&comm_predicate_func_p1name);
        BPredicate_Free(&comm_predicate);
    }
fail1:
    BLog(BLOG_NOTICE, "exiting");
    BLog_Free();
fail0:
    DebugObjectGlobal_Finish();
    
    return 1;
}

void terminate (void)
{
    BLog(BLOG_NOTICE, "tearing down");
    
    // exit event loop
    BReactor_Quit(&ss, 0);
}

void print_help (const char *name)
{
    printf(
        "Usage:\n"
        "    %s\n"
        "        [--help]\n"
        "        [--version]\n"
        "        [--logger <"LOGGERS_STRING">]\n"
        #ifndef BADVPN_USE_WINAPI
        "        (logger=syslog?\n"
        "            [--syslog-facility <string>]\n"
        "            [--syslog-ident <string>]\n"
        "        )\n"
        #endif
        "        [--loglevel <0-5/none/error/warning/notice/info/debug>]\n"
        "        [--channel-loglevel <channel-name> <0-5/none/error/warning/notice/info/debug>] ...\n"
        "        [--listen-addr <addr>] ...\n"
        "        [--ssl --nssdb <string> --server-cert-name <string>]\n"
        "        [--comm-predicate <string>]\n"
        "        [--relay-predicate <string>]\n"
        "Address format is a.b.c.d:port (IPv4) or [addr]:port (IPv6).\n",
        name
    );
}

void print_version (void)
{
    printf(GLOBAL_PRODUCT_NAME" "PROGRAM_NAME" "GLOBAL_VERSION"\n"GLOBAL_COPYRIGHT_NOTICE"\n");
}

int parse_arguments (int argc, char *argv[])
{
    options.help = 0;
    options.version = 0;
    options.logger = LOGGER_STDOUT;
    #ifndef BADVPN_USE_WINAPI
    options.logger_syslog_facility = "daemon";
    options.logger_syslog_ident = argv[0];
    #endif
    options.loglevel = -1;
    for (int i = 0; i < BLOG_NUM_CHANNELS; i++) {
        options.loglevels[i] = -1;
    }
    options.ssl = 0;
    options.nssdb = NULL;
    options.server_cert_name = NULL;
    options.num_listen_addrs = 0;
    options.comm_predicate = NULL;
    options.relay_predicate = NULL;
    
    for (int i = 1; i < argc; i++) {
        char *arg = argv[i];
        if (!strcmp(arg, "--help")) {
            options.help = 1;
        }
        else if (!strcmp(arg, "--version")) {
            options.version = 1;
        }
        else if (!strcmp(arg, "--logger")) {
            if (i + 1 >= argc) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            char *arg2 = argv[i + 1];
            if (!strcmp(arg2, "stdout")) {
                options.logger = LOGGER_STDOUT;
            }
            #ifndef BADVPN_USE_WINAPI
            else if (!strcmp(arg2, "syslog")) {
                options.logger = LOGGER_SYSLOG;
            }
            #endif
            else {
                fprintf(stderr, "%s: wrong argument\n", arg);
                return 0;
            }
            i++;
        }
        #ifndef BADVPN_USE_WINAPI
        else if (!strcmp(arg, "--syslog-facility")) {
            if (i + 1 >= argc) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            options.logger_syslog_facility = argv[i + 1];
            i++;
        }
        else if (!strcmp(arg, "--syslog-ident")) {
            if (i + 1 >= argc) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            options.logger_syslog_ident = argv[i + 1];
            i++;
        }
        #endif
        else if (!strcmp(arg, "--loglevel")) {
            if (1 >= argc - i) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            if ((options.loglevel = parse_loglevel(argv[i + 1])) < 0) {
                fprintf(stderr, "%s: wrong argument\n", arg);
                return 0;
            }
            i++;
        }
        else if (!strcmp(arg, "--channel-loglevel")) {
            if (2 >= argc - i) {
                fprintf(stderr, "%s: requires two arguments\n", arg);
                return 0;
            }
            int channel = BLogGlobal_GetChannelByName(argv[i + 1]);
            if (channel < 0) {
                fprintf(stderr, "%s: wrong channel argument\n", arg);
                return 0;
            }
            int loglevel = parse_loglevel(argv[i + 2]);
            if (loglevel < 0) {
                fprintf(stderr, "%s: wrong loglevel argument\n", arg);
                return 0;
            }
            options.loglevels[channel] = loglevel;
            i += 2;
        }
        else if (!strcmp(arg, "--ssl")) {
            options.ssl = 1;
        }
        else if (!strcmp(arg, "--nssdb")) {
            if (1 >= argc - i) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            options.nssdb = argv[i + 1];
            i++;
        }
        else if (!strcmp(arg, "--server-cert-name")) {
            if (1 >= argc - i) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            options.server_cert_name = argv[i + 1];
            i++;
        }
        else if (!strcmp(arg, "--listen-addr")) {
            if (1 >= argc - i) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            if (options.num_listen_addrs == MAX_LISTEN_ADDRS) {
                fprintf(stderr, "%s: too many\n", arg);
                return 0;
            }
            options.listen_addrs[options.num_listen_addrs] = argv[i + 1];
            options.num_listen_addrs++;
            i++;
        }
        else if (!strcmp(arg, "--comm-predicate")) {
            if (1 >= argc - i) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            options.comm_predicate = argv[i + 1];
            i++;
        }
        else if (!strcmp(arg, "--relay-predicate")) {
            if (1 >= argc - i) {
                fprintf(stderr, "%s: requires an argument\n", arg);
                return 0;
            }
            options.relay_predicate = argv[i + 1];
            i++;
        }
        else {
            fprintf(stderr, "%s: unknown option\n", arg);
            return 0;
        }
    }
    
    if (options.help || options.version) {
        return 1;
    }
    
    if (!!options.nssdb != options.ssl) {
        fprintf(stderr, "--ssl and --nssdb must be used together\n");
        return 0;
    }
    
    if (!!options.server_cert_name != options.ssl) {
        fprintf(stderr, "--ssl and --server-cert-name must be used together\n");
        return 0;
    }
    
    return 1;
}

int process_arguments (void)
{
    // resolve listen addresses
    num_listen_addrs = 0;
    while (num_listen_addrs < options.num_listen_addrs) {
        if (!BAddr_Parse(&listen_addrs[num_listen_addrs], options.listen_addrs[num_listen_addrs], NULL, 0)) {
            BLog(BLOG_ERROR, "listen addr: BAddr_Parse failed");
            return 0;
        }
        num_listen_addrs++;
    }
    
    return 1;
}

void signal_handler (void *unused)
{
    BLog(BLOG_NOTICE, "termination requested");
    
    terminate();
    return;
}

void listener_handler (Listener *listener)
{
    if (clients_num == MAX_CLIENTS) {
        BLog(BLOG_WARNING, "too many clients for new client");
        goto fail0;
    }
    
    // allocate the client structure
    struct client_data *client = malloc(sizeof(*client));
    if (!client) {
        BLog(BLOG_ERROR, "failed to allocate client");
        goto fail0;
    }
    
    // accept it
    if (!Listener_Accept(listener, &client->sock, &client->addr)) {
        BLog(BLOG_NOTICE, "Listener_Accept failed");
        goto fail1;
    }
    
    client_add(client);
    return;
    
fail1:
    free(client);
fail0:
    ;
}

void client_add (struct client_data *client)
{
    ASSERT(clients_num < MAX_CLIENTS)
    
    // assign ID
    client->id = new_client_id();
    
    // set no common name
    client->common_name = NULL;
    
    // now client_log() works
    
    if (options.ssl) {
        // initialize SSL
        
        // create BSocket NSPR file descriptor
        BSocketPRFileDesc_Create(&client->bottom_prfd, &client->sock);
        
        // create SSL file descriptor from the socket's BSocketPRFileDesc
        if (!(client->ssl_prfd = SSL_ImportFD(model_prfd, &client->bottom_prfd))) {
            client_log(client, BLOG_ERROR, "SSL_ImportFD failed");
            ASSERT_FORCE(PR_Close(&client->bottom_prfd) == PR_SUCCESS)
            goto fail0;
        }
        
        // set server mode
        if (SSL_ResetHandshake(client->ssl_prfd, PR_TRUE) != SECSuccess) {
            client_log(client, BLOG_ERROR, "SSL_ResetHandshake failed");
            goto fail1;
        }
        
        // set require client certificate
        if (SSL_OptionSet(client->ssl_prfd, SSL_REQUEST_CERTIFICATE, PR_TRUE) != SECSuccess) {
            client_log(client, BLOG_ERROR, "SSL_OptionSet(SSL_REQUEST_CERTIFICATE) failed");
            goto fail1;
        }
        if (SSL_OptionSet(client->ssl_prfd, SSL_REQUIRE_CERTIFICATE, PR_TRUE) != SECSuccess) {
            client_log(client, BLOG_ERROR, "SSL_OptionSet(SSL_REQUIRE_CERTIFICATE) failed");
            goto fail1;
        }
        
        // initialize BPRFileDesc on SSL file descriptor
        BPRFileDesc_Init(&client->ssl_bprfd, client->ssl_prfd);
    } else {
        // initialize I/O
        if (!client_init_io(client)) {
            goto fail0;
        }
    }
    
    // start disconnect timer
    BTimer_Init(&client->disconnect_timer, CLIENT_NO_DATA_TIME_LIMIT, (BTimer_handler)client_disconnect_timer_handler, client);
    BReactor_SetTimer(&ss, &client->disconnect_timer);
    
    // link in
    clients_num++;
    LinkedList2_Append(&clients, &client->list_node);
    ASSERT_EXECUTE(BAVL_Insert(&clients_tree, &client->tree_node, NULL))
    
    // init knowledge lists
    LinkedList2_Init(&client->know_out_list);
    LinkedList2_Init(&client->know_in_list);
    
    // initialize peer flows from us list and tree (flows for sending messages to other clients)
    LinkedList2_Init(&client->peer_out_flows_list);
    BAVL_Init(&client->peer_out_flows_tree, OFFSET_DIFF(struct peer_flow, dest_client_id, src_tree_node), (BAVL_comparator)peerid_comparator, NULL);
    
    // init dying
    client->dying = 0;
    BPending_Init(&client->dying_job, BReactor_PendingGroup(&ss), (BPending_handler)client_dying_job, client);
    
    // set state
    client->initstatus = (options.ssl ? INITSTATUS_HANDSHAKE : INITSTATUS_WAITHELLO);
    
    client_log(client, BLOG_INFO, "initialized");
    
    // start I/O
    if (options.ssl) {
        // set read handler for driving handshake
        BPRFileDesc_AddEventHandler(&client->ssl_bprfd, PR_POLL_READ, (BPRFileDesc_handler)client_handshake_read_handler, client);
        
        // start handshake
        client_try_handshake(client);
        return;
    } else {
        return;
    }
    
    // cleanup on errors
fail1:
    if (options.ssl) {
        ASSERT_FORCE(PR_Close(client->ssl_prfd) == PR_SUCCESS)
    }
fail0:
    BSocket_Free(&client->sock);
    free(client);
}

void client_remove (struct client_data *client)
{
    ASSERT(!client->dying)
    
    client_log(client, BLOG_NOTICE, "removing");
    
    // set dying to prevent sending this client anything
    client->dying = 1;
    
    // free I/O (including incoming flows)
    if (client->initstatus >= INITSTATUS_WAITHELLO) {
        client_dealloc_io(client);
    }
    
    // remove outgoing knows
    LinkedList2Node *node;
    while (node = LinkedList2_GetFirst(&client->know_out_list)) {
        struct peer_know *k = UPPER_OBJECT(node, struct peer_know, from_node);
        remove_know(k);
    }
    
    // remove outgoing flows
    while (node = LinkedList2_GetFirst(&client->peer_out_flows_list)) {
        struct peer_flow *flow = UPPER_OBJECT(node, struct peer_flow, src_list_node);
        ASSERT(flow->src_client == client)
        ASSERT(flow->dest_client->initstatus == INITSTATUS_COMPLETE && !flow->dest_client->dying)
        
        if (PacketPassFairQueueFlow_IsBusy(&flow->qflow)) {
            client_log(client, BLOG_DEBUG, "removing flow later");
            peer_flow_disconnect(flow);
            PacketPassFairQueueFlow_SetBusyHandler(&flow->qflow, (PacketPassFairQueue_handler_busy)peer_flow_handler_canremove, flow);
        } else {
            client_log(client, BLOG_DEBUG, "removing flow now");
            peer_flow_dealloc(flow);
        }
    }
    
    // schedule job to finish removal after clients are informed
    BPending_Set(&client->dying_job);
    
    // inform other clients that 'client' is no more
    LinkedList2Iterator it;
    LinkedList2Iterator_InitForward(&it, &client->know_in_list);
    while (node = LinkedList2Iterator_Next(&it)) {
        struct peer_know *k = UPPER_OBJECT(node, struct peer_know, to_node);
        uninform_know(k);
    }
}

void client_dying_job (struct client_data *client)
{
    ASSERT(client->dying)
    ASSERT(LinkedList2_IsEmpty(&client->know_in_list))
    
    client_dealloc(client);
    return;
}

void client_dealloc (struct client_data *client)
{
    ASSERT(LinkedList2_IsEmpty(&client->know_out_list))
    ASSERT(LinkedList2_IsEmpty(&client->know_in_list))
    ASSERT(LinkedList2_IsEmpty(&client->peer_out_flows_list))
    
    // free I/O
    if (client->initstatus >= INITSTATUS_WAITHELLO && !client->dying) {
        client_dealloc_io(client);
    }
    
    // free dying
    BPending_Free(&client->dying_job);
    
    // link out
    BAVL_Remove(&clients_tree, &client->tree_node);
    LinkedList2_Remove(&clients, &client->list_node);
    clients_num--;
    
    // stop disconnect timer
    BReactor_RemoveTimer(&ss, &client->disconnect_timer);
    
    // free SSL
    if (options.ssl) {
        // free BPRFileDesc
        BPRFileDesc_Free(&client->ssl_bprfd);
        
        // free SSL PRFD
        ASSERT_FORCE(PR_Close(client->ssl_prfd) == PR_SUCCESS)
    }
    
    // free common name
    if (client->common_name) {
        PORT_Free(client->common_name);
    }
    
    // free socket
    BSocket_Free(&client->sock);
    
    // free memory
    free(client);
}

void client_log (struct client_data *client, int level, const char *fmt, ...)
{
    va_list vl;
    va_start(vl, fmt);
    char addr[BADDR_MAX_PRINT_LEN];
    BAddr_Print(&client->addr, addr);
    BLog_Append("client %d (%s)", (int)client->id, addr);
    if (client->common_name) {
        BLog_Append(" (%s)", client->common_name);
    }
    BLog_Append(": ");
    BLog_LogToChannelVarArg(BLOG_CURRENT_CHANNEL, level, fmt, vl);
    va_end(vl);
}

void client_disconnect_timer_handler (struct client_data *client)
{
    ASSERT(!client->dying)
    
    client_log(client, BLOG_NOTICE, "timed out");
    
    client_remove(client);
    return;
}

void client_try_handshake (struct client_data *client)
{
    ASSERT(client->initstatus == INITSTATUS_HANDSHAKE)
    ASSERT(!client->dying)
    
    // attempt handshake
    if (SSL_ForceHandshake(client->ssl_prfd) != SECSuccess) {
        PRErrorCode error = PR_GetError();
        if (error == PR_WOULD_BLOCK_ERROR) {
            // try again on read event
            BPRFileDesc_EnableEvent(&client->ssl_bprfd, PR_POLL_READ);
            return;
        }
        client_log(client, BLOG_NOTICE, "SSL_ForceHandshake failed (%d)", (int)error);
        goto fail0;
    }
    
    // remove read handler
    BPRFileDesc_RemoveEventHandler(&client->ssl_bprfd, PR_POLL_READ);
    
    // get client certificate
    CERTCertificate *cert = SSL_PeerCertificate(client->ssl_prfd);
    if (!cert) {
        client_log(client, BLOG_ERROR, "SSL_PeerCertificate failed");
        goto fail0;
    }
    
    // remember common name
    if (!(client->common_name = CERT_GetCommonName(&cert->subject))) {
        client_log(client, BLOG_NOTICE, "CERT_GetCommonName failed");
        goto fail1;
    }
    
    // store certificate
    SECItem der = cert->derCert;
    if (der.len > sizeof(client->cert)) {
        client_log(client, BLOG_NOTICE, "client certificate too big");
        goto fail1;
    }
    memcpy(client->cert, der.data, der.len);
    client->cert_len = der.len;
    
    PRArenaPool *arena = PORT_NewArena(DER_DEFAULT_CHUNKSIZE);
    if (!arena) {
        client_log(client, BLOG_ERROR, "PORT_NewArena failed");
        goto fail1;
    }
    
    // encode certificate
    memset(&der, 0, sizeof(der));
    if (!SEC_ASN1EncodeItem(arena, &der, cert, SEC_ASN1_GET(CERT_CertificateTemplate))) {
        client_log(client, BLOG_ERROR, "SEC_ASN1EncodeItem failed");
        goto fail2;
    }
    
    // store re-encoded certificate (for compatibility with old clients)
    if (der.len > sizeof(client->cert_old)) {
        client_log(client, BLOG_NOTICE, "client certificate too big");
        goto fail2;
    }
    memcpy(client->cert_old, der.data, der.len);
    client->cert_old_len = der.len;
    
    // init I/O chains
    if (!client_init_io(client)) {
        goto fail2;
    }
    
    PORT_FreeArena(arena, PR_FALSE);
    CERT_DestroyCertificate(cert);
    
    // set client state
    client->initstatus = INITSTATUS_WAITHELLO;
    
    client_log(client, BLOG_INFO, "handshake complete");
    
    return;
    
    // handle errors
fail2:
    PORT_FreeArena(arena, PR_FALSE);
fail1:
    CERT_DestroyCertificate(cert);
fail0:
    client_remove(client);
}

void client_handshake_read_handler (struct client_data *client, PRInt16 event)
{
    ASSERT(client->initstatus == INITSTATUS_HANDSHAKE)
    ASSERT(!client->dying)
    ASSERT(event == PR_POLL_READ)
    
    // restart no data timer
    BReactor_SetTimer(&ss, &client->disconnect_timer);
    
    // continue handshake
    client_try_handshake(client);
    return;
}

int client_init_io (struct client_data *client)
{
    // initialize error domain
    FlowErrorDomain_Init(&client->domain, (FlowErrorDomain_handler)client_error_handler, client);
    
    // init input
    
    // init source
    StreamRecvInterface *source_interface;
    if (options.ssl) {
        PRStreamSource_Init(&client->input_source.ssl, FlowErrorReporter_Create(&client->domain, COMPONENT_SOURCE), &client->ssl_bprfd, BReactor_PendingGroup(&ss));
        source_interface = PRStreamSource_GetOutput(&client->input_source.ssl);
    } else {
        StreamSocketSource_Init(&client->input_source.plain, FlowErrorReporter_Create(&client->domain, COMPONENT_SOURCE), &client->sock, BReactor_PendingGroup(&ss));
        source_interface = StreamSocketSource_GetOutput(&client->input_source.plain);
    }
    
    // init interface
    PacketPassInterface_Init(&client->input_interface, SC_MAX_ENC, (PacketPassInterface_handler_send)client_input_handler_send, client, BReactor_PendingGroup(&ss));
    
    // init decoder
    if (!PacketProtoDecoder_Init(
        &client->input_decoder, FlowErrorReporter_Create(&client->domain, COMPONENT_DECODER),
        source_interface, &client->input_interface, BReactor_PendingGroup(&ss)
    )) {
        client_log(client, BLOG_ERROR, "PacketProtoDecoder_Init failed");
        goto fail1;
    }
    
    // init output common
    
    // init sink
    StreamPassInterface *sink_interface;
    if (options.ssl) {
        PRStreamSink_Init(&client->output_sink.ssl, FlowErrorReporter_Create(&client->domain, COMPONENT_SINK), &client->ssl_bprfd, BReactor_PendingGroup(&ss));
        sink_interface = PRStreamSink_GetInput(&client->output_sink.ssl);
    } else {
        StreamSocketSink_Init(&client->output_sink.plain, FlowErrorReporter_Create(&client->domain, COMPONENT_SINK), &client->sock, BReactor_PendingGroup(&ss));
        sink_interface = StreamSocketSink_GetInput(&client->output_sink.plain);
    }
    
    // init sender
    PacketStreamSender_Init(&client->output_sender, sink_interface, PACKETPROTO_ENCLEN(SC_MAX_ENC), BReactor_PendingGroup(&ss));
    
    // init queue
    PacketPassPriorityQueue_Init(&client->output_priorityqueue, PacketStreamSender_GetInput(&client->output_sender), BReactor_PendingGroup(&ss), 0);
    
    // init output control flow
    
    // init queue flow
    PacketPassPriorityQueueFlow_Init(&client->output_control_qflow, &client->output_priorityqueue, -1);
    
    // init PacketProtoFlow
    if (!PacketProtoFlow_Init(
        &client->output_control_oflow, SC_MAX_ENC, CLIENT_CONTROL_BUFFER_MIN_PACKETS,
        PacketPassPriorityQueueFlow_GetInput(&client->output_control_qflow), BReactor_PendingGroup(&ss)
    )) {
        client_log(client, BLOG_ERROR, "PacketProtoFlow_Init failed");
        goto fail2;
    }
    client->output_control_input = PacketProtoFlow_GetInput(&client->output_control_oflow);
    client->output_control_packet_len = -1;
    
    // init output peers flow
    
    // init queue flow
    // use lower priority than control flow (higher number)
    PacketPassPriorityQueueFlow_Init(&client->output_peers_qflow, &client->output_priorityqueue, 0);
    
    // init fair queue (for different peers)
    PacketPassFairQueue_Init(&client->output_peers_fairqueue, PacketPassPriorityQueueFlow_GetInput(&client->output_peers_qflow), BReactor_PendingGroup(&ss), 0, 1);
    
    // init list of flows
    LinkedList2_Init(&client->output_peers_flows);
    
    return 1;
    
fail2:
    PacketPassPriorityQueueFlow_Free(&client->output_control_qflow);
    // free output common
    PacketPassPriorityQueue_Free(&client->output_priorityqueue);
    PacketStreamSender_Free(&client->output_sender);
    if (options.ssl) {
        PRStreamSink_Free(&client->output_sink.ssl);
    } else {
        StreamSocketSink_Free(&client->output_sink.plain);
    }
    // free input
    PacketProtoDecoder_Free(&client->input_decoder);
fail1:
    PacketPassInterface_Free(&client->input_interface);
    if (options.ssl) {
        PRStreamSource_Free(&client->input_source.ssl);
    } else {
        StreamSocketSource_Free(&client->input_source.plain);
    }
    return 0;
}

void client_dealloc_io (struct client_data *client)
{
    // allow freeing fair queue flows
    PacketPassFairQueue_PrepareFree(&client->output_peers_fairqueue);
    
    // remove flows to us
    LinkedList2Node *node;
    while (node = LinkedList2_GetFirst(&client->output_peers_flows)) {
        struct peer_flow *flow = UPPER_OBJECT(node, struct peer_flow, dest_list_node);
        ASSERT(flow->dest_client == client)
        peer_flow_dealloc(flow);
    }
    
    // allow freeing priority queue flows
    PacketPassPriorityQueue_PrepareFree(&client->output_priorityqueue);
    
    // free output peers flow
    PacketPassFairQueue_Free(&client->output_peers_fairqueue);
    PacketPassPriorityQueueFlow_Free(&client->output_peers_qflow);
    
    // free output control flow
    PacketProtoFlow_Free(&client->output_control_oflow);
    PacketPassPriorityQueueFlow_Free(&client->output_control_qflow);
    
    // free output common
    PacketPassPriorityQueue_Free(&client->output_priorityqueue);
    PacketStreamSender_Free(&client->output_sender);
    if (options.ssl) {
        PRStreamSink_Free(&client->output_sink.ssl);
    } else {
        StreamSocketSink_Free(&client->output_sink.plain);
    }
    
    // free input
    PacketProtoDecoder_Free(&client->input_decoder);
    PacketPassInterface_Free(&client->input_interface);
    if (options.ssl) {
        PRStreamSource_Free(&client->input_source.ssl);
    } else {
        StreamSocketSource_Free(&client->input_source.plain);
    }
}

void client_error_handler (struct client_data *client, int component, int code)
{
    ASSERT(INITSTATUS_HASLINK(client->initstatus))
    ASSERT(!client->dying)
    
    client_log(client, BLOG_NOTICE, "error");
    
    client_remove(client);
    return;
}

int client_start_control_packet (struct client_data *client, void **data, int len)
{
    ASSERT(len >= 0)
    ASSERT(len <= SC_MAX_PAYLOAD)
    ASSERT(!(len > 0) || data)
    ASSERT(INITSTATUS_HASLINK(client->initstatus))
    ASSERT(!client->dying)
    ASSERT(client->output_control_packet_len == -1)
    
    // obtain location for writing the packet
    if (!BufferWriter_StartPacket(client->output_control_input, &client->output_control_packet)) {
        // out of buffer, kill client
        client_log(client, BLOG_NOTICE, "out of control buffer, removing");
        client_remove(client);
        return -1;
    }
    
    client->output_control_packet_len = len;
    
    if (data) {
        *data = client->output_control_packet + sizeof(struct sc_header);
    }
    
    return 0;
}

void client_end_control_packet (struct client_data *client, uint8_t type)
{
    ASSERT(INITSTATUS_HASLINK(client->initstatus))
    ASSERT(!client->dying)
    ASSERT(client->output_control_packet_len >= 0)
    ASSERT(client->output_control_packet_len <= SC_MAX_PAYLOAD)
    
    // write header
    struct sc_header *header = (struct sc_header *)client->output_control_packet;
    header->type = htol8(type);
    
    // finish writing packet
    BufferWriter_EndPacket(client->output_control_input, sizeof(struct sc_header) + client->output_control_packet_len);
    
    client->output_control_packet_len = -1;
}

int client_send_newclient (struct client_data *client, struct client_data *nc, int relay_server, int relay_client)
{
    ASSERT(client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!client->dying)
    ASSERT(nc->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!nc->dying)
    
    int flags = 0;
    if (relay_server) {
        flags |= SCID_NEWCLIENT_FLAG_RELAY_SERVER;
    }
    if (relay_client) {
        flags |= SCID_NEWCLIENT_FLAG_RELAY_CLIENT;
    }
    
    uint8_t *cert_data = NULL;
    int cert_len = 0;
    if (options.ssl) {
        cert_data = (client->version == SC_OLDVERSION ?  nc->cert_old : nc->cert);
        cert_len = (client->version == SC_OLDVERSION ?  nc->cert_old_len : nc->cert_len);
    }
    
    struct sc_server_newclient *pack;
    if (client_start_control_packet(client, (void **)&pack, sizeof(struct sc_server_newclient) + cert_len) < 0) {
        return -1;
    }
    pack->id = htol16(nc->id);
    pack->flags = htol16(flags);
    memcpy(pack + 1, cert_data, cert_len);
    client_end_control_packet(client, SCID_NEWCLIENT);
    
    return 0;
}

int client_send_endclient (struct client_data *client, peerid_t end_id)
{
    ASSERT(client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!client->dying)
    
    struct sc_server_endclient *pack;
    if (client_start_control_packet(client, (void **)&pack, sizeof(struct sc_server_endclient)) < 0) {
        return -1;
    }
    pack->id = htol16(end_id);
    client_end_control_packet(client, SCID_ENDCLIENT);
    
    return 0;
}

void client_input_handler_send (struct client_data *client, uint8_t *data, int data_len)
{
    ASSERT(data_len >= 0)
    ASSERT(data_len <= SC_MAX_ENC)
    ASSERT(INITSTATUS_HASLINK(client->initstatus))
    ASSERT(!client->dying)
    
    if (data_len < sizeof(struct sc_header)) {
        client_log(client, BLOG_NOTICE, "packet too short");
        client_remove(client);
        return;
    }
    
    struct sc_header *header = (struct sc_header *)data;
    uint8_t type = ltoh8(header->type);
    
    uint8_t *sc_data = data + sizeof(struct sc_header);
    int sc_data_len = data_len - sizeof(struct sc_header);
    
    ASSERT(sc_data_len >= 0)
    ASSERT(sc_data_len <= SC_MAX_PAYLOAD)
    
    // restart no data timer
    BReactor_SetTimer(&ss, &client->disconnect_timer);
    
    // accept packet
    PacketPassInterface_Done(&client->input_interface);
    
    // perform action based on packet type
    switch (type) {
        case SCID_KEEPALIVE:
            client_log(client, BLOG_DEBUG, "received keep-alive");
            return;
        case SCID_CLIENTHELLO:
            process_packet_hello(client, sc_data, sc_data_len);
            return;
        case SCID_OUTMSG:
            process_packet_outmsg(client, sc_data, sc_data_len);
            return;
        default:
            client_log(client, BLOG_NOTICE, "unknown packet type %d, removing", (int)header->type);
            client_remove(client);
            return;
    }
}

void process_packet_hello (struct client_data *client, uint8_t *data, int data_len)
{
    if (client->initstatus != INITSTATUS_WAITHELLO) {
        client_log(client, BLOG_NOTICE, "hello: not expected");
        client_remove(client);
        return;
    }
    
    if (data_len != sizeof(struct sc_client_hello)) {
        client_log(client, BLOG_NOTICE, "hello: invalid length");
        client_remove(client);
        return;
    }
    
    struct sc_client_hello *msg = (struct sc_client_hello *)data;
    client->version = ltoh16(msg->version);
    
    if (client->version != SC_VERSION && client->version != SC_OLDVERSION) {
        client_log(client, BLOG_NOTICE, "hello: unknown version");
        client_remove(client);
        return;
    }
    
    client_log(client, BLOG_INFO, "received hello");
    
    // limit socket send buffer, else our scheduling is pointless
    if (BSocket_SetSendBuffer(&client->sock, CLIENT_SOCKET_SEND_BUFFER) < 0) {
        BLog(BLOG_WARNING, "BSocket_SetSendBuffer failed");
    }
    
    // set client state to complete
    client->initstatus = INITSTATUS_COMPLETE;
    
    // publish client
    for (LinkedList2Node *list_node = LinkedList2_GetFirst(&clients); list_node; list_node = LinkedList2Node_Next(list_node)) {
        struct client_data *client2 = UPPER_OBJECT(list_node, struct client_data, list_node);
        if (client2 == client || client2->initstatus != INITSTATUS_COMPLETE || client2->dying || !clients_allowed(client, client2)) {
            continue;
        }
        
        // determine relay relations
        int relay_to = relay_allowed(client, client2);
        int relay_from = relay_allowed(client2, client);
        
        if (!create_know(client, client2, relay_to, relay_from)) {
            client_log(client, BLOG_ERROR, "failed to allocate know to %d", (int)client2->id);
            goto fail;
        }
        
        if (!create_know(client2, client, relay_from, relay_to)) {
            client_log(client, BLOG_ERROR, "failed to allocate know from %d", (int)client2->id);
            goto fail;
        }
        
        // create flow from client to client2
        if (!peer_flow_create(client, client2)) {
            client_log(client, BLOG_ERROR, "failed to allocate flow to %d", (int)client2->id);
            goto fail;
        }
        
        // create flow from client2 to client
        if (!peer_flow_create(client2, client)) {
            client_log(client, BLOG_ERROR, "failed to allocate flow from %d", (int)client2->id);
            goto fail;
        }
    }
    
    // send hello
    struct sc_server_hello *pack;
    if (client_start_control_packet(client, (void **)&pack, sizeof(struct sc_server_hello)) < 0) {
        return;
    }
    pack->flags = htol16(0);
    pack->id = htol16(client->id);
    pack->clientAddr = (client->addr.type == BADDR_TYPE_IPV4 ? client->addr.ipv4.ip : htol32(0));
    client_end_control_packet(client, SCID_SERVERHELLO);
    
    return;
    
fail:
    client_remove(client);
}

void process_packet_outmsg (struct client_data *client, uint8_t *data, int data_len)
{
    if (client->initstatus != INITSTATUS_COMPLETE) {
        client_log(client, BLOG_NOTICE, "outmsg: not expected");
        client_remove(client);
        return;
    }
    
    if (data_len < sizeof(struct sc_client_outmsg)) {
        client_log(client, BLOG_NOTICE, "outmsg: wrong size");
        client_remove(client);
        return;
    }
    
    struct sc_client_outmsg *msg = (struct sc_client_outmsg *)data;
    peerid_t id = ltoh16(msg->clientid);
    int payload_size = data_len - sizeof(struct sc_client_outmsg);
    
    if (payload_size > SC_MAX_MSGLEN) {
        client_log(client, BLOG_NOTICE, "outmsg: too large payload");
        client_remove(client);
        return;
    }
    
    uint8_t *payload = data + sizeof(struct sc_client_outmsg);
    
    // lookup flow to destination client
    BAVLNode *node = BAVL_LookupExact(&client->peer_out_flows_tree, &id);
    if (!node) {
        client_log(client, BLOG_INFO, "no flow for message to %d", (int)id);
        return;
    }
    struct peer_flow *flow = UPPER_OBJECT(node, struct peer_flow, src_tree_node);
    
    // send packet
    struct sc_server_inmsg *pack;
    if (!peer_flow_start_packet(flow, (void **)&pack, sizeof(struct sc_server_inmsg) + payload_size)) {
        return;
    }
    pack->clientid = htol16(client->id);
    memcpy((uint8_t *)(pack + 1), payload, payload_size);
    peer_flow_end_packet(flow, SCID_INMSG);
}

struct peer_flow * peer_flow_create (struct client_data *src_client, struct client_data *dest_client)
{
    ASSERT(src_client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!src_client->dying)
    ASSERT(dest_client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!dest_client->dying)
    ASSERT(!BAVL_LookupExact(&src_client->peer_out_flows_tree, &dest_client->id))
    
    // allocate flow structure
    struct peer_flow *flow = malloc(sizeof(*flow));
    if (!flow) {
        goto fail0;
    }
    
    // set source and destination
    flow->src_client = src_client;
    flow->dest_client = dest_client;
    flow->dest_client_id = dest_client->id;
    
    // add to source list and tree
    LinkedList2_Append(&flow->src_client->peer_out_flows_list, &flow->src_list_node);
    ASSERT_EXECUTE(BAVL_Insert(&flow->src_client->peer_out_flows_tree, &flow->src_tree_node, NULL))
    
    // add to destination client list
    LinkedList2_Append(&flow->dest_client->output_peers_flows, &flow->dest_list_node);
    
    // initialize I/O
    PacketPassFairQueueFlow_Init(&flow->qflow, &flow->dest_client->output_peers_fairqueue);
    if (!PacketProtoFlow_Init(
        &flow->oflow, SC_MAX_ENC, CLIENT_PEER_FLOW_BUFFER_MIN_PACKETS,
        PacketPassFairQueueFlow_GetInput(&flow->qflow), BReactor_PendingGroup(&ss)
    )) {
        BLog(BLOG_ERROR, "PacketProtoFlow_Init failed");
        goto fail1;
    }
    flow->input = PacketProtoFlow_GetInput(&flow->oflow);
    flow->packet_len = -1;
    
    return flow;
    
fail1:
    PacketPassFairQueueFlow_Free(&flow->qflow);
    LinkedList2_Remove(&flow->dest_client->output_peers_flows, &flow->dest_list_node);
    BAVL_Remove(&flow->src_client->peer_out_flows_tree, &flow->src_tree_node);
    LinkedList2_Remove(&flow->src_client->peer_out_flows_list, &flow->src_list_node);
    free(flow);
fail0:
    return NULL;
}

void peer_flow_dealloc (struct peer_flow *flow)
{
    PacketPassFairQueueFlow_AssertFree(&flow->qflow);
    
    // free I/O
    PacketProtoFlow_Free(&flow->oflow);
    PacketPassFairQueueFlow_Free(&flow->qflow);
    
    // remove from destination client list
    LinkedList2_Remove(&flow->dest_client->output_peers_flows, &flow->dest_list_node);
    
    // remove from source list and hash table
    if (flow->src_client) {
        BAVL_Remove(&flow->src_client->peer_out_flows_tree, &flow->src_tree_node);
        LinkedList2_Remove(&flow->src_client->peer_out_flows_list, &flow->src_list_node);
    }
    
    // free memory
    free(flow);
}

void peer_flow_disconnect (struct peer_flow *flow)
{
    ASSERT(flow->src_client)
    
    // remove from source list and hash table
    BAVL_Remove(&flow->src_client->peer_out_flows_tree, &flow->src_tree_node);
    LinkedList2_Remove(&flow->src_client->peer_out_flows_list, &flow->src_list_node);
    
    // set no source
    flow->src_client = NULL;
}

int peer_flow_start_packet (struct peer_flow *flow, void **data, int len)
{
    ASSERT(len >= 0)
    ASSERT(len <= SC_MAX_PAYLOAD)
    ASSERT(!(len > 0) || data)
    ASSERT(flow->dest_client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!flow->dest_client->dying)
    ASSERT(flow->src_client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!flow->src_client->dying)
    ASSERT(flow->packet_len == -1)
    
    // obtain location for writing the packet
    if (!BufferWriter_StartPacket(flow->input, &flow->packet)) {
        client_log(flow->src_client, BLOG_INFO, "out of flow buffer for message to %d", (int)flow->dest_client->id);
        return 0;
    }
    
    flow->packet_len = len;
    
    if (data) {
        *data = flow->packet + sizeof(struct sc_header);
    }
    
    return 1;
}

void peer_flow_end_packet (struct peer_flow *flow, uint8_t type)
{
    ASSERT(flow->packet_len >= 0)
    ASSERT(flow->packet_len <= SC_MAX_PAYLOAD)
    
    // write header
    struct sc_header *header = (struct sc_header *)flow->packet;
    header->type = type;
    
    // finish writing packet
    BufferWriter_EndPacket(flow->input, sizeof(struct sc_header) + flow->packet_len);
    
    flow->packet_len = -1;
}

void peer_flow_handler_canremove (struct peer_flow *flow)
{
    ASSERT(!flow->src_client)
    ASSERT(flow->dest_client->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!flow->dest_client->dying)
    
    client_log(flow->dest_client, BLOG_DEBUG, "removing old flow");
    
    peer_flow_dealloc(flow);
    return;
}

peerid_t new_client_id (void)
{
    ASSERT(clients_num < MAX_CLIENTS)
    
    for (int i = 0; i < MAX_CLIENTS; i++) {
        peerid_t id = clients_nextid++;
        if (!find_client_by_id(id)) {
            return id;
        }
    }
    
    ASSERT(0)
    return 42;
}

struct client_data * find_client_by_id (peerid_t id)
{
    BAVLNode *node;
    if (!(node = BAVL_LookupExact(&clients_tree, &id))) {
        return NULL;
    }
    
    return UPPER_OBJECT(node, struct client_data, tree_node);
}

int clients_allowed (struct client_data *client1, struct client_data *client2)
{
    ASSERT(client1->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!client1->dying)
    ASSERT(client2->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!client2->dying)
    
    if (!options.comm_predicate) {
        return 1;
    }
    
    // set values to compare against
    comm_predicate_p1name = (client1->common_name ? client1->common_name : "");
    comm_predicate_p2name = (client2->common_name ? client2->common_name : "");
    BAddr_GetIPAddr(&client1->addr, &comm_predicate_p1addr);
    BAddr_GetIPAddr(&client2->addr, &comm_predicate_p2addr);
    
    // evaluate predicate
    int res = BPredicate_Eval(&comm_predicate);
    if (res < 0) {
        return 0;
    }
    
    return res;
}

int comm_predicate_func_p1name_cb (void *user, void **args)
{
    char *arg = args[0];
    
    return (!strcmp(arg, comm_predicate_p1name));
}

int comm_predicate_func_p2name_cb (void *user, void **args)
{
    char *arg = args[0];
    
    return (!strcmp(arg, comm_predicate_p2name));
}

int comm_predicate_func_p1addr_cb (void *user, void **args)
{
    char *arg = args[0];
    
    BIPAddr addr;
    if (!BIPAddr_Resolve(&addr, arg, 1)) {
        BLog(BLOG_WARNING, "failed to parse address");
        return -1;
    }
    
    return BIPAddr_Compare(&addr, &comm_predicate_p1addr);
}

int comm_predicate_func_p2addr_cb (void *user, void **args)
{
    char *arg = args[0];
    
    BIPAddr addr;
    if (!BIPAddr_Resolve(&addr, arg, 1)) {
        BLog(BLOG_WARNING, "failed to parse address");
        return -1;
    }
    
    return BIPAddr_Compare(&addr, &comm_predicate_p2addr);
}

int relay_allowed (struct client_data *client, struct client_data *relay)
{
    if (!options.relay_predicate) {
        return 0;
    }
    
    // set values to compare against
    relay_predicate_pname = (client->common_name ? client->common_name : "");
    relay_predicate_rname = (relay->common_name ? relay->common_name : "");
    BAddr_GetIPAddr(&client->addr, &relay_predicate_paddr);
    BAddr_GetIPAddr(&relay->addr, &relay_predicate_raddr);
    
    // evaluate predicate
    int res = BPredicate_Eval(&relay_predicate);
    if (res < 0) {
        return 0;
    }
    
    return res;
}

int relay_predicate_func_pname_cb (void *user, void **args)
{
    char *arg = args[0];
    
    return (!strcmp(arg, relay_predicate_pname));
}

int relay_predicate_func_rname_cb (void *user, void **args)
{
    char *arg = args[0];
    
    return (!strcmp(arg, relay_predicate_rname));
}

int relay_predicate_func_paddr_cb (void *user, void **args)
{
    char *arg = args[0];
    
    BIPAddr addr;
    if (!BIPAddr_Resolve(&addr, arg, 1)) {
        BLog(BLOG_ERROR, "paddr: failed to parse address");
        return -1;
    }
    
    return BIPAddr_Compare(&addr, &relay_predicate_paddr);
}

int relay_predicate_func_raddr_cb (void *user, void **args)
{
    char *arg = args[0];
    
    BIPAddr addr;
    if (!BIPAddr_Resolve(&addr, arg, 1)) {
        BLog(BLOG_ERROR, "raddr: failed to parse address");
        return -1;
    }
    
    return BIPAddr_Compare(&addr, &relay_predicate_raddr);
}

int peerid_comparator (void *unused, peerid_t *p1, peerid_t *p2)
{
    if (*p1 < *p2) {
        return -1;
    }
    if (*p1 > *p2) {
        return 1;
    }
    return 0;
}

int create_know (struct client_data *from, struct client_data *to, int relay_server, int relay_client)
{
    ASSERT(from->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!from->dying)
    ASSERT(to->initstatus == INITSTATUS_COMPLETE)
    ASSERT(!to->dying)
    
    // allocate structure
    struct peer_know *k = malloc(sizeof(*k));
    if (!k) {
        return 0;
    }
    
    // init arguments
    k->from = from;
    k->to = to;
    k->relay_server = relay_server;
    k->relay_client = relay_client;
    
    // append to lists
    LinkedList2_Append(&from->know_out_list, &k->from_node);
    LinkedList2_Append(&to->know_in_list, &k->to_node);
    
    // init and set inform job to inform client 'from' about client 'to'
    BPending_Init(&k->inform_job, BReactor_PendingGroup(&ss), (BPending_handler)know_inform_job_handler, k);
    BPending_Set(&k->inform_job);
    
    // init uninform job
    BPending_Init(&k->uninform_job, BReactor_PendingGroup(&ss), (BPending_handler)know_uninform_job_handler, k);
    
    return 1;
}

void remove_know (struct peer_know *k)
{
    // free uninform job
    BPending_Free(&k->uninform_job);
    
    // free inform job
    BPending_Free(&k->inform_job);
    
    // remove from lists
    LinkedList2_Remove(&k->to->know_in_list, &k->to_node);
    LinkedList2_Remove(&k->from->know_out_list, &k->from_node);
    
    // free structure
    free(k);
}

void know_inform_job_handler (struct peer_know *k)
{
    ASSERT(!k->from->dying)
    ASSERT(!k->to->dying)
    
    client_send_newclient(k->from, k->to, k->relay_server, k->relay_client);
    return;
}

void uninform_know (struct peer_know *k)
{
    ASSERT(!k->from->dying)
    ASSERT(k->to->dying)
    ASSERT(!BPending_IsSet(&k->uninform_job))
    
    // if 'from' has not been informed about 'to' yet, remove know, otherwise
    // schedule informing 'from' that 'to' is no more
    if (BPending_IsSet(&k->inform_job)) {
        remove_know(k);
    } else {
        BPending_Set(&k->uninform_job);
    }
}

void know_uninform_job_handler (struct peer_know *k)
{
    ASSERT(!k->from->dying)
    ASSERT(k->to->dying)
    ASSERT(!BPending_IsSet(&k->inform_job))
    
    struct client_data *from = k->from;
    struct client_data *to = k->to;
    
    // remove know
    remove_know(k);
    
    // uninform
    client_send_endclient(from, to->id);
}