| 1 | #include <errno.h> |
| 2 | #include <stdio.h> |
| 3 | #include <stdlib.h> |
| 4 | #include <string.h> |
| 5 | |
| 6 | #include <sys/types.h> |
| 7 | #include <unistd.h> |
| 8 | #include <sys/socket.h> |
| 9 | #include <netinet/in.h> |
| 10 | #include <net/if.h> |
| 11 | #include <sys/ioctl.h> |
| 12 | |
| 13 | int main(int argc, char *argv[]) |
| 14 | { |
| 15 | int fd; |
| 16 | struct ifreq ifr; |
| 17 | if (argc != 2) { |
| 18 | fprintf(stderr, "usage: %s IFACE\n", argv[0]); |
| 19 | exit(1); |
| 20 | } |
| 21 | if (strlen(argv[1]) >= sizeof(ifr.ifr_name)) { |
| 22 | fprintf(stderr, "%s: interface name `%s' too long\n", argv[0], argv[1]); |
| 23 | exit(1); |
| 24 | } |
| 25 | if ((fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) { |
| 26 | fprintf(stderr, "%s: socket: %s\n", argv[0], strerror(errno)); |
| 27 | exit(1); |
| 28 | } |
| 29 | strcpy(ifr.ifr_name, argv[1]); |
| 30 | if (ioctl(fd, SIOCGIFMTU, &ifr)) { |
| 31 | fprintf(stderr, "%s: ioctl(SIOCGIFMTU): %s\n", argv[0], strerror(errno)); |
| 32 | exit(1); |
| 33 | } |
| 34 | printf("%d\n", ifr.ifr_mtu); |
| 35 | return (0); |
| 36 | } |