To produce packets with extended IP header setsockopt operation can be performed with level SOL_IP and option IP_OPTIONS:
int ipoption=0xbaadf00d;
int sockfd=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
setsockopt(sockfd, SOL_IP, IP_OPTIONS, &ipoption, sizeof ipoption);
After making this when trying to connect TCP stack produces packets with correct extended header. Problem is how to do the same for server socket: I expect TCP server socket that answers with SYN/ACK packet with specific IP header extension in response to connect. But making same setsockopt for socket gives no effect. No matter when I call setsockopt - before listen, before accept etc. Is it possible somehow to apply IP option to server socket without switching to RAW sockets?