196 lines
4.5 KiB
C
196 lines
4.5 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* This is a variation of the BSD IPC Tutorial
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* streamreader. In this variation, we allow the user
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* to specify whether to only listen on IPv4, only on
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* IPv6, or to use a dual-stack socket.
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*
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* ./a.out [4|6]
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*/
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#include <arpa/inet.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#define BACKLOG 5
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/* Everything is stuffed into one giant 'main' here to
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* allow the reader to follow step-by-step without
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* having to jump around. Normally, you'd probably
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* want to modularize this a bit. */
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int
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main(int argc, char **argv)
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{
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int domain, sock, v4or6;
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void *s;
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socklen_t length, s_size;
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struct sockaddr_storage server;
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if (argc > 2) {
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(void)fprintf(stderr, "Usage: %s [4|6]\n", argv[0]);
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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/* Default is IPv6, but we then become dual
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* stack by disabling IPV6_ONLY on the socket. */
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v4or6 = 6;
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if (argc == 2) {
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v4or6 = atoi(argv[1]);
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if ((v4or6 != 4) && (v4or6 != 6)) {
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(void)fprintf(stderr, "Usage: %s [4|6]\n", argv[0]);
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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}
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domain = (v4or6 == 4) ? PF_INET : PF_INET6;
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if ((sock = socket(domain, SOCK_STREAM, 0)) < 0) {
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perror("opening stream socket");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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if (domain == PF_INET) {
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struct sockaddr_in *sin = (struct sockaddr_in *)&server;
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memset(sin, 0, sizeof(*sin));
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sin->sin_family = PF_INET;
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sin->sin_addr.s_addr = INADDR_ANY;
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sin->sin_port = 0;
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s = sin;
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s_size = sizeof(*sin);
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} else {
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struct sockaddr_in6 *sin = (struct sockaddr_in6 *)&server;
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memset(sin, 0, sizeof(*sin));
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sin->sin6_family = PF_INET6;
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sin->sin6_addr = in6addr_any;
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sin->sin6_port = 0;
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s = sin;
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s_size = sizeof(*sin);
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/* Neither v4 nor v6 was explicitly
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* requested, so we do both. */
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if (argc == 1) {
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int off = 0;
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if (setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (void *)&off, sizeof(off)) < 0) {
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perror("setsockopt");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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}
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}
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if (bind(sock, (struct sockaddr *)s, s_size) != 0) {
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perror("binding stream socket");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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/* Find out assigned port number and print it out */
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length = sizeof(server);
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if (getsockname(sock, (struct sockaddr *)&server, &length) != 0) {
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perror("getting socket name");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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int num;
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if (domain == PF_INET) {
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struct sockaddr_in *s = (struct sockaddr_in *)&server;
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num = ntohs(s->sin_port);
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} else {
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struct sockaddr_in6 *s = (struct sockaddr_in6 *)&server;
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num = ntohs(s->sin6_port);
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}
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(void)printf("Socket has port #%d\n", num);
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if (listen(sock, BACKLOG) < 0) {
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perror("listening");
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exit(EXIT_FAILURE);
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/* NOTREACHED */
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}
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while (1) {
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int fd, rval;
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struct sockaddr_in6 client;
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memset(&client, 0, sizeof(client));
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length = sizeof(client);
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if ((fd = accept(sock, (struct sockaddr *)&client, &length)) < 0) {
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perror("accept");
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continue;
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}
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do {
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char buf[BUFSIZ];
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char claddr[INET6_ADDRSTRLEN];
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struct sockaddr_storage addr;
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socklen_t len;
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const char *rip;
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int port;
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bzero(buf, sizeof(buf));
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if ((rval = read(fd, buf, BUFSIZ)) < 0) {
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perror("reading stream message");
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break;
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}
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if (rval == 0) {
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(void)printf("Ending connection\n");
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break;
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}
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len = sizeof(addr);
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if (getpeername(fd, (struct sockaddr *)&addr, &len) < 0) {
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perror("getpeername");
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break;
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}
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if (domain == PF_INET) {
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struct sockaddr_in *s = (struct sockaddr_in *)&addr;
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port = ntohs(s->sin_port);
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rip = inet_ntop(PF_INET, &s->sin_addr, claddr, sizeof(claddr));
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} else {
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struct sockaddr_in6 *s = (struct sockaddr_in6 *)&addr;
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port = ntohs(s->sin6_port);
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rip = inet_ntop(PF_INET6, &s->sin6_addr, claddr, sizeof(claddr));
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}
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if (rip == NULL) {
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perror("inet_ntop");
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rip = "unknown";
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}
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(void)printf("Client (%s:%d) sent: \"%s\"", rip, port, buf);
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} while (rval != 0);
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(void)close(fd);
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}
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/* NOTREACHED */
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}
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