mtu.c revision a45056e35c1af2a0f0a6eed258fd5fdf4846a79f 
1/*
2 * Copyright 2011 Daniel Drown
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * mtu.c - get interface mtu
17 */
18
19#include <string.h>
20#include <stdlib.h>
21#include <sys/types.h>
22#include <sys/socket.h>
23#include <sys/ioctl.h>
24#include <net/if.h>
25
26#include "mtu.h"
27
28/* function: getifmtu
29 * returns the interface mtu or -1 on failure
30 * ifname - interface name
31 */
32int getifmtu(const char *ifname) {
33  int fd;
34  struct ifreq if_mtu;
35
36  fd = socket(AF_INET, SOCK_STREAM, 0);
37  if(fd < 0) {
38    return -1;
39  }
40  strncpy(if_mtu.ifr_name, ifname, IFNAMSIZ);
41  if_mtu.ifr_name[IFNAMSIZ - 1] = '\0';
42  if(ioctl(fd, SIOCGIFMTU, &if_mtu) < 0) {
43    return -1;
44  }
45  return if_mtu.ifr_mtu;
46}
47