diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/Makefile | 5 | ||||
| -rw-r--r-- | src/broadcaster.c | 74 | ||||
| -rw-r--r-- | src/common.h | 8 | ||||
| -rw-r--r-- | src/listener.c | 119 |
4 files changed, 206 insertions, 0 deletions
diff --git a/src/Makefile b/src/Makefile new file mode 100644 index 0000000..6e3d3db --- /dev/null +++ b/src/Makefile @@ -0,0 +1,5 @@ +all: broadcaster listener + +.PHONY: clean +clean: + rm -f broadcaster listener *~ diff --git a/src/broadcaster.c b/src/broadcaster.c new file mode 100644 index 0000000..9c02f79 --- /dev/null +++ b/src/broadcaster.c @@ -0,0 +1,74 @@ +/* +** broadcaster.c -- a datagram "client" like talker.c, except +** this one can broadcast +*/ + +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +#include <errno.h> +#include <string.h> +#include <sys/types.h> +#include <sys/socket.h> +#include <netinet/in.h> +#include <arpa/inet.h> +#include <netdb.h> + +#include "common.h" + +int main(int argc, char *argv[]) +{ + int sockfd; + struct sockaddr_in their_addr; // connector's address information + struct hostent *he; + int numbytes; + int broadcast = 1; + + // assemble packet + if (argc < 3 || argc > 4) { + fprintf(stderr,"usage: broadcaster hostname task [message]\n"); + exit(1); + } + char buf[MAXBUFLEN], + *task = argv[2], + *message = (argc == 4) ? argv[3] : NULL; + int task_len = strlen(task), + total_len = task_len + 1 + strlen(message); + if (total_len > MAXBUFLEN) { + fprintf(stderr,"payload to long: max %d bytes, was %d\n", MAXBUFLEN, total_len); + exit(1); + } + strcpy(buf, task); + buf[task_len] = 0; + strcpy(buf + 1 + task_len, message); + + if ((he=gethostbyname(argv[1])) == NULL) { // get the host info + perror("gethostbyname"); + exit(1); + } + + if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { + perror("socket"); + exit(1); + } + + // this call is what allows broadcast packets to be sent: + if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast, + sizeof broadcast) == -1) { + perror("setsockopt (SO_BROADCAST)"); + exit(1); + } + + their_addr.sin_family = AF_INET; // host byte order + their_addr.sin_port = htons(SERVERPORT); // short, network byte order + their_addr.sin_addr = *((struct in_addr *)he->h_addr); + memset(their_addr.sin_zero, '\0', sizeof their_addr.sin_zero); + + if ((numbytes=sendto(sockfd, buf, total_len, 0, + (struct sockaddr *)&their_addr, sizeof their_addr)) == -1) { + perror("sendto"); + exit(1); + } + + return 0; +} diff --git a/src/common.h b/src/common.h new file mode 100644 index 0000000..c64c764 --- /dev/null +++ b/src/common.h @@ -0,0 +1,8 @@ +#ifndef UDP_BROADCAST_COMMON +#define UDP_BROADCAST_COMMON + +#define SERVERPORT 4950 // the port users will be connecting to +#define SERVERPORT_S "4950" +#define MAXBUFLEN 100 + +#endif // UDP_BROADCAST_COMMON diff --git a/src/listener.c b/src/listener.c new file mode 100644 index 0000000..c0d81ef --- /dev/null +++ b/src/listener.c @@ -0,0 +1,119 @@ +/* +** listener.c -- a datagram sockets "server" demo +*/ + +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +#include <errno.h> +#include <string.h> +#include <sys/types.h> +#include <sys/socket.h> +#include <netinet/in.h> +#include <arpa/inet.h> +#include <netdb.h> + +#include "common.h" + +// get sockaddr, IPv4 or IPv6: +void *get_in_addr(struct sockaddr *sa) +{ + if (sa->sa_family == AF_INET) { + return &(((struct sockaddr_in*)sa)->sin_addr); + } + + return &(((struct sockaddr_in6*)sa)->sin6_addr); +} + +int main(int argc, char *argv[], char *envp[]) +{ + int sockfd; + struct addrinfo hints, *servinfo, *p; + int rv; + int numbytes; + struct sockaddr_storage their_addr; + char buf[MAXBUFLEN]; + socklen_t addr_len; + char s[INET6_ADDRSTRLEN]; + + memset(&hints, 0, sizeof hints); + hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4 + hints.ai_socktype = SOCK_DGRAM; + hints.ai_flags = AI_PASSIVE; // use my IP + + if ((rv = getaddrinfo(NULL, SERVERPORT_S, &hints, &servinfo)) != 0) { + fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); + return 1; + } + + // loop through all the results and bind to the first we can + for(p = servinfo; p != NULL; p = p->ai_next) { + if ((sockfd = socket(p->ai_family, p->ai_socktype, + p->ai_protocol)) == -1) { + perror("listener: socket"); + continue; + } + + if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { + close(sockfd); + perror("listener: bind"); + continue; + } + + break; + } + + if (p == NULL) { + fprintf(stderr, "listener: failed to bind socket\n"); + return 2; + } + + freeaddrinfo(servinfo); + + // daemonize +#ifndef DEBUG + switch (fork()) { + case 0: + setsid(); + umask(0); + break; + case -1: + perror("fork (serious!)"); + exit(-1); + default: + exit(0); + } +#endif + + // receive loop + addr_len = sizeof their_addr; + while ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0, + (struct sockaddr *)&their_addr, &addr_len)) != -1) { + // decode packet & launch handler + buf[numbytes] = '\0'; + char *task = buf, + *cl_argv[3] = {task, (strlen(task)<numbytes) ? (buf+strlen(task)+1) : NULL, NULL }; + + if (task[0] == '/' || strstr(task, "..")) { + fprintf(stderr, "payload tried directory traversal\n"); + continue; + } + + switch (fork()) { + case 0: + close(sockfd); // close socket handler, leave std io + execve(task, cl_argv, envp); + perror("exec"); + exit(-1); + case -1: + perror("fork (serious!)"); + exit(-1); + default: + wait(); + } + } + + perror("recvfrom"); + + return -1; +} |