server: add command line option for SO_SNDBUF. Bump default to 16K.

server/server.c

@@ -83,6 +83,7 @@ struct {
     int num_listen_addrs;
     char *comm_predicate;
     char *relay_predicate;
+    int client_sndbuf;
 } options;
 
 // listen addresses
@@ -572,6 +573,7 @@ void print_help (const char *name)
         "        [--ssl --nssdb <string> --server-cert-name <string>]\n"
         "        [--comm-predicate <string>]\n"
         "        [--relay-predicate <string>]\n"
+        "        [--client-sndbuf <bytes / 0>]\n"
         "Address format is a.b.c.d:port (IPv4) or [addr]:port (IPv6).\n",
         name
     );
@@ -601,6 +603,7 @@ int parse_arguments (int argc, char *argv[])
     options.num_listen_addrs = 0;
     options.comm_predicate = NULL;
     options.relay_predicate = NULL;
+    options.client_sndbuf = CLIENT_SOCKET_DEFAULT_SEND_BUFFER;
     
     for (int i = 1; i < argc; i++) {
         char *arg = argv[i];
@@ -725,6 +728,17 @@ int parse_arguments (int argc, char *argv[])
             options.relay_predicate = argv[i + 1];
             i++;
         }
+        else if (!strcmp(arg, "--client-sndbuf")) {
+            if (1 >= argc - i) {
+                fprintf(stderr, "%s: requires an argument\n", arg);
+                return 0;
+            }
+            if ((options.client_sndbuf = atoi(argv[i + 1])) < 0) {
+                fprintf(stderr, "%s: wrong argument\n", arg);
+                return 0;
+            }
+            i++;
+        }
         else {
             fprintf(stderr, "%s: unknown option\n", arg);
             return 0;
@@ -792,7 +806,7 @@ void listener_handler (BListener *listener)
     }
     
     // limit socket send buffer, else our scheduling is pointless
-    if (!BConnection_SetSendBuffer(&client->con, CLIENT_SOCKET_SEND_BUFFER) < 0) {
+    if (!BConnection_SetSendBuffer(&client->con, options.client_sndbuf) < 0) {
         BLog(BLOG_WARNING, "BConnection_SetSendBuffer failed");
     }
     

server/server.h

@@ -47,7 +47,7 @@
 // after how long of not hearing anything from the client we disconnect it
 #define CLIENT_NO_DATA_TIME_LIMIT 30000
 // SO_SNDBFUF socket option for clients
-#define CLIENT_SOCKET_SEND_BUFFER 4096
+#define CLIENT_SOCKET_DEFAULT_SEND_BUFFER 16384
 
 // maxiumum listen addresses
 #define MAX_LISTEN_ADDRS 16