/* * Support functions for dealing with sockets. * * Note: these functions cannot be used out of the box. * In particular, support for protocol independent programming * is not fully implemented. See below. * * Written by G. Back for CS 3214 Spring 2018. * Updated to support client connects. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include "socket.h" static bool silent_mode = false; /* * Find a suitable IPv4 address to bind to, create a socket, bind it, * invoke listen to get the socket ready for accepting clients. * * This function does not implement proper support for protocol-independent/ * dual-stack binding. Adding this is part of the assignment. * * Returns -1 on error, setting errno. * Returns socket file descriptor otherwise. */ int socket_open_bind_listen(char * port_number_string, int backlog) { struct addrinfo *info, *pinfo; struct addrinfo hint; memset(&hint, 0, sizeof hint); hint.ai_flags = AI_PASSIVE | // we're looking for an address to bind to AI_NUMERICSERV; // service port is numeric, don't look in /etc/services hint.ai_protocol = IPPROTO_TCP; // only interested in TCP printf("calling getaddrinfo\n"); int rc = getaddrinfo(NULL, port_number_string, &hint, &info); printf("getaddrinfo returned\n"); if (rc != 0) { fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(rc)); return -1; } // char printed_addr[1024]; for (pinfo = info; pinfo; pinfo = pinfo->ai_next) { assert (pinfo->ai_protocol == IPPROTO_TCP); /* Uncomment this to see the address returned int rc = getnameinfo(pinfo->ai_addr, pinfo->ai_addrlen, printed_addr, sizeof printed_addr, NULL, 0, NI_NUMERICHOST); if (rc != 0) { fprintf(stderr, "getnameinfo error: %s\n", gai_strerror(rc)); return -1; } printf("%s: %s\n", pinfo->ai_family == AF_INET ? "AF_INET" : pinfo->ai_family == AF_INET6 ? "AF_INET6" : "?", printed_addr); */ /* Skip any IPv4 addresses. * IPv6 only */ if (pinfo->ai_family == AF_INET) continue; int s = socket(pinfo->ai_family, pinfo->ai_socktype, pinfo->ai_protocol); if (s == -1) { perror("socket"); return -1; } // See https://stackoverflow.com/a/3233022 for a good explanation of what this does int opt = 1; setsockopt (s, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof (opt)); rc = bind(s, pinfo->ai_addr, pinfo->ai_addrlen); if (rc == -1) { perror("bind"); close(s); return -1; } rc = listen(s, backlog); if (rc == -1) { perror("listen"); close(s); return -1; } freeaddrinfo(info); return s; } fprintf(stderr, "No suitable address to bind port %s found\n", port_number_string); return -1; } /** * Accept a client, blocking if necessary. * * Returns file descriptor of client accepted on success, returns * -1 on error. */ int socket_accept_client(int accepting_socket) { /* The address passed into accept must be large enough for either IPv4 & IPv6. * Using a struct sockaddr is too small to hold a full IPv6 address and accept() * would not return the full address. */ struct sockaddr_storage peer; socklen_t peersize = sizeof(peer); int client = accept(accepting_socket, (struct sockaddr *) &peer, &peersize); if (client == -1) { perror("accept"); return -1; } /* Performance tuning. Turn off Nagle's algorithm. * Otherwise, when the servers sends a reply to the client, and the reply * is small relative to the MSS size, there would be a delay of 40ms * during which the OS would hope in vain for more data to be sent. * See tcp(7) */ int i = 1; setsockopt(client, IPPROTO_TCP, TCP_NODELAY, (void *)&i, sizeof(i)); /* The following will help with debugging your server. * Adjust and/or remove as you see fit. */ if (!silent_mode) { char peer_addr[1024], peer_port[10]; int rc = getnameinfo((struct sockaddr *) &peer, peersize, peer_addr, sizeof peer_addr, peer_port, sizeof peer_port, NI_NUMERICHOST | NI_NUMERICSERV); if (rc != 0) { fprintf(stderr, "getnameinfo error: %s\n", gai_strerror(rc)); return -1; } fprintf(stderr, "Accepted connection from %s:%s\n", peer_addr, peer_port); } return client; } int socket_connect(const char *hostname, const char *port_number_string) { struct addrinfo *info, *pinfo; struct addrinfo hint; memset(&hint, 0, sizeof hint); hint.ai_protocol = IPPROTO_TCP; // only interested in TCP int rc = getaddrinfo(hostname, port_number_string, &hint, &info); if (rc != 0) { fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(rc)); return -1; } for (pinfo = info; pinfo; pinfo = pinfo->ai_next) { int s = socket(pinfo->ai_family, pinfo->ai_socktype, pinfo->ai_protocol); if (s == -1) { perror("socket"); return -1; } rc = connect(s, pinfo->ai_addr, pinfo->ai_addrlen); if (rc == 0) return s; close(s); } return -1; }
