rendered paste body#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
const ssize_t SST_NEG1 = -1;
const size_t ST_NEG1 = -1;
const int SOCK_FALSE = 0;
const int SOCK_TRUE = 1;
#ifdef OFFICIAL
#define PORTNUM 12345
#define DEBUG 0
#else
#define PORTNUM 12345
#define DEBUG 1
#endif
typedef struct {
uint8_t version;
uint8_t ttl;
uint16_t payload_length;
uint32_t account_identifier;
uint32_t source_address;
uint32_t destination_address;
uint16_t checksum;
uint16_t protocol;
} cmsc417_message_header;
int main(int argc, char**argv) {
int ret_val = 0;
#ifdef OFFICIAL
const int MAX_ARGS = 2;
#else
const int MAX_ARGS = 3;
#endif
/* 2^16 - 1 + 1, extra byte so we can definitely append null */
const size_t MAX_SIZE = 65536;
size_t msg_size = 0;
void* msg_bytes = NULL;
cmsc417_message_header head;
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
int sock = 0;
in_addr_t to_in_addr;
memset(&to_in_addr, 0, sizeof(to_in_addr));
socklen_t addr_size = 0;
char* addr_str = NULL;
ssize_t sent_size;
int bind_ret = 0;
void *buf = NULL;
struct ip_mreq group;
memset(&group, 0, sizeof(group));
in_addr_t multi_in_addr;
memset(&multi_in_addr, 0, sizeof(multi_in_addr));
size_t num_recv = 0;
size_t tot_len = 0;
if((2 <= argc) && (argc <= MAX_ARGS)) {
/*************
* Send
*************/
/* Declare and init message */
head.version = 1;
head.ttl = 1;
/* Payload will be a string, argv[1], sans null */
head.payload_length = htons(strlen(argv[1]));
head.account_identifier = htonl(6);
head.source_address = htonl(0);
head.destination_address = htonl(0);
head.checksum = htons(0);
head.protocol = htons(1);
/* XXX this might bite us in the ass if the compiler pads the struct for alignment.
* If it does, just calculate the unaligned size and use that for malloc and memcpy.
*/
msg_size = sizeof(head) + strlen(argv[1]);
msg_bytes = malloc(msg_size);
if(NULL == msg_bytes) {
fprintf(stderr, "Error allocating memory for message: %s\n", strerror(errno));
goto END_SEND;
}
memset(msg_bytes, 0, sizeof(msg_size));
memcpy(msg_bytes, &head, sizeof(head));
memcpy(msg_bytes+sizeof(head), argv[0], strlen(argv[1]));
addr_size = sizeof(addr);
if(argc >= 3) {
addr_str = argv[2];
} else {
addr_str = "224.0.50.111";
}
addr.sin_family = PF_INET;
to_in_addr = inet_addr(addr_str);
if((INADDR_NONE == to_in_addr) && (0 != strncmp("255.255.255.255", addr_str, 15))) {
fprintf(stderr, "Error converting address '%s': %s\n", addr_str, strerror(errno));
goto END_SEND;
}
addr.sin_addr.s_addr = htonl(to_in_addr);
addr.sin_port = htons(12345);
/* SOCK_DGRAM and 0 might not be correct ... */
sock = socket(PF_INET, SOCK_DGRAM, 0);
if(-1 == sock) {
fprintf(stderr, "Error creating send socket: %s\n", strerror(errno));
goto END_SEND;
}
if(-1 == setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &SOCK_TRUE, sizeof(SOCK_TRUE))) {
fprintf(stderr, "Error setting broadcast on send: %s\n", strerror(errno));
close(sock);
goto END_SEND;
}
/* Note: saddr fields were initialized in network byte order */
sent_size = sendto(sock, msg_bytes, msg_size, 0, (struct sockaddr *) &addr, addr_size);
if(DEBUG) { fprintf(stderr, "sent %zu out of %zu bytes\n", sent_size, msg_size); }
if(SST_NEG1 == sent_size) {
fprintf(stderr, "Error sending message: %s\n", strerror(errno));
}
close(sock);
/* Jump Free Memory, Jump! */
END_SEND:
if(NULL != msg_bytes) { free(msg_bytes); msg_bytes = NULL; }
/*************
* Recieve
*************/
sock = socket(PF_INET, SOCK_DGRAM, 0);
if(-1 == sock) {
fprintf(stderr, "Error creating receive socket: %s\n", strerror(errno));
ret_val = 10;
goto END_RECV;
}
if(-1 == setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &SOCK_TRUE, sizeof(SOCK_TRUE))) {
fprintf(stderr, "Error setting reuse addr on recv: %s\n", strerror(errno));
close(sock);
ret_val = 11;
goto END_RECV;
}
/* This is needed on BSD (at least OS X) and shouldn't hurt */
#ifdef SO_REUSEPORT
if(-1 == setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &SOCK_TRUE, sizeof(SOCK_TRUE))) {
fprintf(stderr, "Error setting reuse port on recv: %s\n", strerror(errno));
ret_val = 12;
close(sock);
goto END_RECV;
}
#endif
/* copy the address we sent to */
multi_in_addr = inet_addr(addr_str);
if((INADDR_NONE == multi_in_addr) && (0 != strncmp("255.255.255.255", addr_str, 15))) {
fprintf(stderr, "Error converting address '%s': %s\n", addr_str, strerror(errno));
goto END_RECV;
}
group.imr_multiaddr.s_addr = htonl(multi_in_addr);
group.imr_interface.s_addr = htonl(INADDR_ANY);
if(-1 == setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, &group, sizeof(group))) {
fprintf(stderr, "Error joining group on recv: %s\n", strerror(errno));
close(sock);
ret_val = 13;
goto END_RECV;
}
/* Re-use addr. We can't bind to multicast, I seem to recall+tried */
addr.sin_addr.s_addr = htonl(INADDR_ANY);
bind_ret = bind(sock, (struct sockaddr *) &addr, addr_size);
if(-1 == bind_ret) {
fprintf(stderr, "Error binding to %s:%d: %s\n", addr_str, PORTNUM, strerror(errno));
ret_val = 14;
close(sock);
goto END_RECV;
}
buf = malloc(MAX_SIZE);
if(NULL == msg_bytes) {
fprintf(stderr, "Error allocating memory for buffer: %s\n", strerror(errno));
goto END_RECV;
}
while(1) {
/* Safety first kids (debugging sanity, really) */
memset(buf, 0, sizeof(buf));
/* Why is the addr_size argument a non-const pointer?? */
num_recv = recvfrom(sock, buf, sizeof(buf), MSG_WAITALL, (struct sockaddr *) &addr, &addr_size);
/* size_t num_recv = recv(sock, buf, sizeof(buf), MSG_WAITALL); */
if(DEBUG) { fprintf(stderr, "recieved %zu bytes\n", num_recv); }
if(-1 == num_recv) {
fprintf(stderr, "Error receiving bytes: %d. Continuing ...\n", errno);
continue;
}
if(num_recv >= sizeof(head)) {
memcpy(&head, buf, sizeof(head));
/* Validate */
tot_len = ntohs(head.payload_length) + sizeof(head);
if(DEBUG) {
fprintf(stderr, "tot_len = %zu\n", tot_len);
fprintf(stderr, "head.protocol = %d\n", ntohs(head.protocol));
fprintf(stderr, "head.version = %d\n", head.version);
}
if((1 == ntohs(head.protocol)) && (1 == head.version) &&
(tot_len == num_recv)) {
((char*)buf)[tot_len] = '\0'; /* ensure null termination */
/* Is appending a newline okay? */
printf("%s\n", (char*) buf+sizeof(head));
} else {
if(DEBUG) { fprintf(stderr, "Dropped packet\n"); }
}
}
}
close(sock);
END_RECV:
if(NULL != buf) { free(buf); buf = NULL; }
} else {
fprintf(stderr, "Usage:\n");
#ifdef OFFICIAL
fprintf(stderr, "\tone message\n");
#else
fprintf(stderr, "\tone message [address]\n");
#endif
}
return ret_val;
}