diff options
Diffstat (limited to 'snippets')
| -rw-r--r-- | snippets/udpecho.c | 289 |
1 files changed, 289 insertions, 0 deletions
diff --git a/snippets/udpecho.c b/snippets/udpecho.c new file mode 100644 index 0000000..b918e88 --- /dev/null +++ b/snippets/udpecho.c @@ -0,0 +1,289 @@ +#define _POSIX_C_SOURCE 200112L +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <stdbool.h> +#include <stdint.h> +#include <malloc.h> +#include <inttypes.h> +#include <errno.h> + +#include <getopt.h> +#include <unistd.h> +#include <sys/socket.h> +#include <netinet/in.h> +#include <netinet/udp.h> +#include <arpa/inet.h> +#include <sys/types.h> +#include <netdb.h> + +#define ARGV0 "udpecho" + + +struct { + int bufsize[2]; + struct { + bool help:1; + bool verbose:1; + bool v6only:1; + } flags; +} opts; + +struct { + struct addrinfo *ai; + int fd; +} g; + +static void init_opts (void) { + opts.bufsize[0] = opts.bufsize[1] = -1; +} + +static void init_g (void) { + g.fd = -1; +} + +static void deinit_g (void) { + if (g.ai != NULL) { + freeaddrinfo(g.ai); + g.ai = NULL; + } + + if (g.fd >= 0) { + close(g.fd); + g.fd = -1; + } +} + +static void print_help (void) { + printf("Usage: "ARGV0" [-hv46] [-p PORT/SERVICE] [LISTEN_ADDR]\n"); +} + +static int do_getaddrinfo ( + const char *node, + const char *service, + const int af, + struct addrinfo **res) +{ + struct addrinfo hints = { 0, }; + + hints.ai_family = af; + hints.ai_socktype = SOCK_DGRAM; + hints.ai_flags = AI_PASSIVE; + + return getaddrinfo(node, service, &hints, res);; +} + +static bool parse_args (const int argc, const char **argv) { + int fr; + int af = AF_UNSPEC; + const char *node = NULL; + const char *service = "1114"; + + while (true) { + fr = getopt(argc, (char*const*)argv, "hv46p:"); + if (fr < 0) { + break; + } + + switch (fr) { + case 'h': opts.flags.help = true; break; + case 'v': opts.flags.verbose = true; break; + case '4': + af = AF_INET; + opts.flags.v6only = false; + break; + case '6': + af = AF_INET6; + opts.flags.v6only = true; + break; + case 'p': service = optarg; break; + case '?': return false; + default: abort(); + } + } + + if (argc > optind + 1) { + fprintf(stderr, ARGV0": too many args\n"); + return false; + } + if (argc > optind) { + node = argv[optind]; + } + + fr = do_getaddrinfo(node, service, af, &g.ai); + if (fr != 0) { + const char *msg = gai_strerror(fr); + + if (strchr(service, ':')) { + fprintf(stderr, ARGV0": [%s]:%s: %s\n", node, service, msg); + } + else { + fprintf(stderr, ARGV0": %s:%s: %s\n", node, service, msg); + } + + return false; + } + + return true; +} + +static const struct addrinfo *pick_af ( + const struct addrinfo *list, + const int af) +{ + while (list != NULL) { + if (list->ai_family == af) { + return list; + } + list = list->ai_next; + } + + return NULL; +} + +static int mksock (const int af) { + int fd; + int fr; + int sv; + const struct addrinfo *ai = pick_af(g.ai, af); + + if (ai == NULL) { + errno = ENOENT; + return -1; + } + + fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); + if (fd < 0) { + perror(ARGV0": socket()"); + goto ERR; + } + + sv = 1; + setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &sv, sizeof(sv)); +#ifdef IPV6_V6ONLY // Linux-specific flag + if (opts.flags.v6only) { + sv = 1; + setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &sv, sizeof(sv)); + } +#endif + + fr = bind(fd, ai->ai_addr, ai->ai_addrlen); + if (fr != 0) { + perror(ARGV0": bind()"); + goto ERR; + } + + return fd; +ERR: + close(fd); + return -1; +} + +static void report_remote ( + const struct sockaddr *sa, + const void *data, + const size_t len) +{ + uint16_t hport; + const void *addr_buf; + char addr_str[INET6_ADDRSTRLEN]; + const char *fr; + + switch (sa->sa_family) { + case AF_INET: + addr_buf = &((const struct sockaddr_in*)sa)->sin_addr; + hport = ntohs(((const struct sockaddr_in*)sa)->sin_port); + break; + case AF_INET6: + addr_buf = &((const struct sockaddr_in6*)sa)->sin6_addr; + hport = ntohs(((const struct sockaddr_in6*)sa)->sin6_port); + break; + default: abort(); + } + + fr = inet_ntop(sa->sa_family, addr_buf, addr_str, sizeof(addr_str)); + if (fr != NULL) { + switch (sa->sa_family) { + case AF_INET: + printf("%5zu bytes from %s:%"PRIu16"\n", len, addr_str, hport); + break; + case AF_INET6: + printf("%5zu bytes from [%s]:%"PRIu16"\n", len, addr_str, hport); + break; + } + } +} + +static int server_loop (void) { + // If the flag doesn't get optimised by the compiler, the bitfield access is + // extremely slow. Might as well cache it. + const bool verbose = opts.flags.verbose; + const int send_flags = MSG_NOSIGNAL +#ifdef MSG_DONTWAIT // Linux-specific flag + | MSG_DONTWAIT +#endif + ; + uint8_t buf[UINT16_MAX]; // as per UDP header + union { + struct sockaddr sa; + struct sockaddr_in sin4; + struct sockaddr_in6 sin6; + } addr; + ssize_t iofr; + socklen_t sl; + + while (true) { + sl = sizeof(addr); + iofr = recvfrom(g.fd, buf, sizeof(buf), 0, &addr.sa, &sl); + if (iofr < 0) { + switch (errno) { + case ECONNREFUSED: // ICMP messages + break; + default: + perror(ARGV0": recvfrom()"); + abort(); + } + } + + if (verbose) { + report_remote(&addr.sa, buf, (size_t)iofr); + } + + sendto(g.fd, buf, (size_t)iofr, send_flags, &addr.sa, sl); + } +} + +int main (const int argc, const char **argv) { + static const int AF_AFF[] = { AF_INET6, AF_INET }; + static int ec = 0; + + init_opts(); + init_g(); + + if (!parse_args(argc, argv)) { + ec = 2; + goto END; + } + + if (opts.flags.help) { + print_help(); + ec = 0; + goto END; + } + + for (size_t i = 0; i < sizeof(AF_AFF) / sizeof(AF_AFF[0]); i += 1) { + g.fd = mksock(AF_AFF[i]); + if (g.fd >= 0) { + break; + } + } + if (g.fd < 0) { + ec = 1; + goto END; + } + + ec = server_loop(); +END: + deinit_g(); + return ec; +} |