cmsg_nxthdr.c: No such file or directory

[giagnv]

Hello,

I'm doing some socket programming, I need to access some ancillary data and I use recvmsg().

I iterate through the ancillary data via the CMSG_FIRSTHDR and CMSG_NXTHDR macros as follows:


for (pCmsg = CMSG_FIRSTHDR (&msg); pCmsg != NULL; pCmsg = CMSG_NXTHDR (&msg, pCmsg)) {
...
}


When CMSG_NXTHDR is called my program segfaults because apparently cmsg_nxthdr.c is not found (I get ../sysdeps/unix/sysv/linux/cmsg_nxthdr.c: No such file or directory).

I am on Ubuntu 12.04, I compile with g++ 4.6.3.

Does anybody have a clue on how to fix this?
Thanks,
G

[Bachstelze]

Post the full error message (and your code, obviously).

[giagnv]

OK, here is the code:



#include <errno.h>
#include <stdio.h>
#include <memory.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <signal.h>
#include <unistd.h>

#if defined IP_PKTINFO
# define DSTADDR_SOCKOPT IP_PKTINFO
# define DSTADDR_DATASIZE (CMSG_SPACE(sizeof(struct in_pktinfo)))

# define dstaddr(x) (&(((struct in_pktinfo *)(CMSG_DATA(x)))->ipi_addr))
# define incomingIface(x) (((struct in_pktinfo *)(CMSG_DATA(x)))->ipi_ifindex)
#else
# error "can't determine socket option"
#endif

int sockfd = 0;

ssize_t ifaceInfoReceiveFrom (int s, void *buf, size_t len, int flags, struct sockaddr *from, socklen_t *fromlen)
{
struct iovec iov;
iov.iov_base = buf;
iov.iov_len = len;

struct cmsghdr *pCmsg;
struct msghdr msg;
msg.msg_name = (caddr_t)from;
msg.msg_namelen = (uint)*fromlen;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = &pCmsg;
msg.msg_controllen = sizeof (cmsghdr);
msg.msg_flags = 0;

size_t rc = recvmsg (s, &msg, flags);
if (rc < 0) {
return -1;
}

*fromlen = msg.msg_namelen;

/* and arrange for IP_RECVDSTADDR to be available */
if (msg.msg_controllen > 0) {
for (pCmsg = CMSG_FIRSTHDR (&msg); pCmsg != NULL; pCmsg = CMSG_NXTHDR (&msg, pCmsg)) {
printf ("Found level %u\n", pCmsg->cmsg_level);
if (pCmsg->cmsg_level == IPPROTO_IP && pCmsg->cmsg_type == DSTADDR_SOCKOPT) {
struct in_addr *to = (struct in_addr *) dstaddr (pCmsg);
unsigned long ulIface = incomingIface (pCmsg);
printf ("The incoming interface is %u\n", ulIface);
break;
}
}
}

return rc;
}

int receive (void *pBuf, int iBufSize)
{
if ((pBuf == NULL) || (iBufSize <= 0)) {
return -1;
}
int rc;
sockaddr_in sa;
socklen_t saSourceLen = sizeof (sa);

if ((rc = ifaceInfoReceiveFrom (sockfd, (char*)pBuf, iBufSize, 0, (struct sockaddr*) &sa, &saSourceLen)) < 0) {
if (errno == EINTR) {
// Some signal interrupted this call - just return 0 for timeout
return 0;
}
else {
return -3;
}
}

return rc;
}

int main()
{
//======================================
// Socket Creation and Initialization
//======================================
sockfd = (int) socket (PF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (sockfd < 0) {
return -1;
}

int opt_val = 1;
if (setsockopt (sockfd, IPPROTO_IP, DSTADDR_SOCKOPT, (char*)&opt_val, sizeof (opt_val)) == -1) {
return -2;
}

struct sockaddr_in local;
memset (&local, 0, sizeof (local));
local.sin_family = AF_INET;
local.sin_port = htons (9999);
local.sin_addr.s_addr = 0; // Listen on wildcard address
memset ((void*) local.sin_zero, 0, sizeof (local.sin_zero));

//enables local address reuse
if (setsockopt (sockfd, SOL_SOCKET, SO_REUSEADDR, (char*)&opt_val, sizeof (opt_val)) < 0) {
return -2;
}

#if defined (OSX)

//enables duplicate address and port bindings
if (setsockopt (sockfd, SOL_SOCKET, SO_REUSEPORT, (char*)&opt_val, sizeof (opt_val)) < 0) {
return -3;
}

#endif

//enables permission to transmit broadcast messages
if (setsockopt (sockfd, SOL_SOCKET, SO_BROADCAST, (char*) &opt_val, sizeof (opt_val)) < 0) {
return -5;
}

//bind the socket to a specified address (INADDR_ANY if not specified) and port
if (bind (sockfd, (struct sockaddr *) &local, sizeof (local)) < 0) {
return -6;
}

//======================================
// Receive
//======================================
for (char buf[1024]; true;) {
if (receive (buf, 1024) == 0)
printf ("Received packet\n");
else
printf ("Error Receiving packet");
}
}


And here is the gdb back trace:



35 ../sysdeps/unix/sysv/linux/cmsg_nxthdr.c: No such file or directory.
(gdb) bt
#0 __cmsg_nxthdr (mhdr=0xbfffecfc, cmsg=0x7fffda40) at ../sysdeps/unix/sysv/linux/cmsg_nxthdr.c:35
#1 0x080486b4 in ifaceInfoReceiveFrom (s=7, buf=0xbfffedcc, len=1024, flags=0, from=0xbfffed7c, fromlen=0xbfffed74) at ../udpsocket.cpp:55
#2 0x0804872a in receive (pBuf=0xbfffedcc, iBufSize=1024) at ../udpsocket.cpp:78
#3 0x0804891c in main () at ../udpsocket.cpp:141


Thanks!