diff --git a/contrib/tools/server/Makefile b/contrib/tools/server/Makefile new file mode 100644 index 00000000000..d7c7d758686 --- /dev/null +++ b/contrib/tools/server/Makefile @@ -0,0 +1,6 @@ +server: + $(CC) -g -o server server.c + +clean: + rm server + diff --git a/contrib/tools/server/README.md b/contrib/tools/server/README.md new file mode 100644 index 00000000000..f962c2c640b --- /dev/null +++ b/contrib/tools/server/README.md @@ -0,0 +1,25 @@ +# Sample TCP Server + +This is a simple TCP server that listens on the specified port (3490 by default) and replies to incoming connections by providing info about src/destination ip/port. + +It demonstrates the use of the getsockopt() system call with the ORIGINAL_DST option to retrieve the original destination ip/port after an iptables redirect. + +So, for example, if you have the server listening on port 3490 on the local machine and an iptables rule like: + +``` +iptables -t nat -I OUTPUT 1 -p tcp --dport 4000:5000 -j REDIRECT --to-port 3490 +``` +your will see: + +``` +$ telnet localhost 3490 +FROM 127.0.0.1:44978, TO 127.0.0.1:3490, ORIG DEST 127.0.0.1:3490 + +$ telnet localhost 4100 +FROM 127.0.0.1:35476, TO 127.0.0.1:3490, ORIG DEST 127.0.0.1:4100 + +$ telnet 1.1.1.1 5000 +FROM 100.100.100.100:60275, TO 127.0.0.1:3490, ORIG DEST 1.1.1.1:5000 +``` + + diff --git a/contrib/tools/server/server.c b/contrib/tools/server/server.c new file mode 100644 index 00000000000..77a2d97e004 --- /dev/null +++ b/contrib/tools/server/server.c @@ -0,0 +1,169 @@ +/* +** server.c + * Demo server to check that we can extract all parameters from an incoming +*request + * and respond to it +*/ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define DEFAULT_PORT \ + "3490" // the port users will be connecting to, if not specified on command + // line + +#define QUEUE_SIZE 10 // pending connections queue size + +void sigchld_handler(int s) { + int saved_errno = errno; + + while (waitpid(-1, NULL, WNOHANG) > 0) + ; + + errno = saved_errno; +} + +int main(int argc, char *argv[]) { + struct sigaction sa; + const int yes = 1; + char *port = DEFAULT_PORT; + int rv; + + if (argc > 1) { + port = argv[1]; + } + + struct addrinfo hints; + memset(&hints, 0, sizeof hints); + hints.ai_family = AF_INET; + hints.ai_socktype = SOCK_STREAM; + hints.ai_flags = AI_PASSIVE; // use my IP + + struct addrinfo *server_info = NULL; + if ((rv = getaddrinfo(NULL, port, &hints, &server_info)) != 0) { + fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); + return 1; + } + + struct addrinfo *p; + int sockfd; // listen on sock_fd + for (p = server_info; p != NULL; p = p->ai_next) { + if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { + perror("server: socket"); + continue; + } + + if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) { + perror("setsockopt"); + exit(1); + } + + if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { + close(sockfd); + perror("server: bind"); + continue; + } + + break; + } + + freeaddrinfo(server_info); + + if (p == NULL) { + fprintf(stderr, "server: failed to bind\n"); + exit(1); + } + if (listen(sockfd, QUEUE_SIZE) == -1) { + perror("listen"); + exit(1); + } + + sa.sa_handler = sigchld_handler; + sigemptyset(&sa.sa_mask); + sa.sa_flags = SA_RESTART; + if (sigaction(SIGCHLD, &sa, NULL) == -1) { + perror("sigaction"); + exit(1); + } + + char bind_addr_str[INET6_ADDRSTRLEN] = {0}; + struct sockaddr_in *bind_sock_addr = (struct sockaddr_in *)p->ai_addr; + inet_ntop(p->ai_family, &bind_sock_addr->sin_addr, bind_addr_str, + p->ai_addrlen); + printf("server %s: waiting for connections on port %s:%u...\n", port, + bind_addr_str, ntohs(bind_sock_addr->sin_port)); + + while (1) { + socklen_t addr_len = sizeof(struct sockaddr_storage); + int addr_str_len = INET6_ADDRSTRLEN; + + struct sockaddr_storage their_addr = { + 0}; // connector's address information + int accepted_fd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_len); + if (accepted_fd == -1) { + perror("accept"); + continue; + } + + struct sockaddr_in *src_sock_addr = (struct sockaddr_in *)&their_addr; + char their_addr_str[INET6_ADDRSTRLEN] = {0}; + inet_ntop(their_addr.ss_family, &src_sock_addr->sin_addr, their_addr_str, + addr_str_len); + printf("server %s: got connection FROM %s:%u\n", port, their_addr_str, + ntohs(src_sock_addr->sin_port)); + + struct sockaddr_storage my_addr = {0}; // my address information + struct sockaddr_in *dst_sock_addr = (struct sockaddr_in *)&my_addr; + char my_addr_str[INET6_ADDRSTRLEN] = {0}; + getsockname(accepted_fd, (struct sockaddr *)dst_sock_addr, &addr_len); + inet_ntop(my_addr.ss_family, &dst_sock_addr->sin_addr, my_addr_str, + addr_str_len); + printf("server %s: got connection TO %s:%u\n", port, my_addr_str, + ntohs(dst_sock_addr->sin_port)); + + struct sockaddr_storage orig_addr = {0}; // orig address information + struct sockaddr_in *orig_sock_addr = (struct sockaddr_in *)&orig_addr; + char orig_addr_str[INET6_ADDRSTRLEN] = {0}; + int status = getsockopt(accepted_fd, SOL_IP, SO_ORIGINAL_DST, + orig_sock_addr, &addr_len); + + if (status == 0) { + inet_ntop(orig_addr.ss_family, &orig_sock_addr->sin_addr, orig_addr_str, + addr_str_len); + printf("server %s: ORIG DEST %s:%u\n", port, orig_addr_str, + ntohs(orig_sock_addr->sin_port)); + } else { + printf("Could not get orig destination from accepted socket.\n"); + } + + if (!fork()) { // this is the child process + + close(sockfd); + char msg[256] = {0}; + snprintf(msg, 256, "FROM %s:%u, TO %s:%u, ORIG DEST %s:%u\n", + their_addr_str, ntohs(src_sock_addr->sin_port), my_addr_str, + ntohs(dst_sock_addr->sin_port), orig_addr_str, + ntohs(orig_sock_addr->sin_port)); + + if (send(accepted_fd, msg, strlen(msg), 0) == -1) { + perror("send"); + } + close(accepted_fd); + exit(0); + } + close(accepted_fd); + } + + return 0; +}