misc: add get_iface_info

misc/get_iface_info.h

@@ -0,0 +1,110 @@
+/**
+ * @file get_iface_info.h
+ * @author Ambroz Bizjak <ambrop7@gmail.com>
+ * 
+ * @section LICENSE
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the author nor the
+ *    names of its contributors may be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef BADVPN_GETIFACEINFO_H
+#define BADVPN_GETIFACEINFO_H
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <net/if.h>
+#include <net/if_arp.h>
+#include <sys/ioctl.h>
+
+#include <misc/debug.h>
+
+/**
+ * Returns information about a network interface with the given name.
+ * 
+ * @param ifname name of interface to get information for
+ * @param out_mac the MAC address will be returned here, unless NULL
+ * @param out_mtu the MTU will be returned here, unless NULL
+ * @param out_ifindex the interface index will be returned here, unless NULL
+ * @return 1 on success, 0 on failure
+ */
+static int get_iface_info (const char *ifname, uint8_t *out_mac, int *out_mtu, int *out_ifindex) WARN_UNUSED;
+
+
+static int get_iface_info (const char *ifname, uint8_t *out_mac, int *out_mtu, int *out_ifindex)
+{
+    ASSERT(ifname)
+    
+    struct ifreq ifr;
+    
+    int s = socket(AF_INET, SOCK_DGRAM, 0);
+    if (!s) {
+        goto fail0;
+    }
+    
+    // get MAC
+    if (out_mac) {
+        memset(&ifr, 0, sizeof(ifr));
+        snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", ifname);
+        if (ioctl(s, SIOCGIFHWADDR, &ifr)) {
+            goto fail1;
+        }
+        if (ifr.ifr_hwaddr.sa_family != ARPHRD_ETHER) {
+            goto fail1;
+        }
+        memcpy(out_mac, ifr.ifr_hwaddr.sa_data, 6);
+    }
+    
+    // get MTU
+    if (out_mtu) {
+        memset(&ifr, 0, sizeof(ifr));
+        snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", ifname);
+        if (ioctl(s, SIOCGIFMTU, &ifr)) {
+            goto fail1;
+        }
+        *out_mtu = ifr.ifr_mtu;
+    }
+    
+    // get interface index
+    if (out_ifindex) {
+        memset(&ifr, 0, sizeof(ifr));
+        snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", ifname);
+        if (ioctl(s, SIOCGIFINDEX, &ifr)) {
+            goto fail1;
+        }
+        *out_ifindex = ifr.ifr_ifindex;
+    }
+    
+    close(s);
+    
+    return 1;
+    
+fail1:
+    close(s);
+fail0:
+    return 0;
+}
+
+#endif