The applicable code is below, as is the exact error.
sd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
if ( setsockopt( sd, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on) ) < 0 )
{
printf("%s\n", strerror(errno));
}
if ( setsockopt( sd, IPPROTO_IP, IP_DF, &on, sizeof(on) ) < 0 )
{
printf("%s\n", strerror(errno));
printf("DF\n");
}
Error:
root@PC:~# gcc main.c
main.c: In function ‘main’:
main.c:71: warning: format not a string literal and no format arguments
root@PC:~# ./a.out localhost
Protocol not available
DF
It's odd that the second setsockopt is erroring, while the first one isn't.
Best Answer
IP_DF
is a packet flag, not a socket option. Valid socket options are given in theip(7)
man page.