On Tue, Oct 31, 2006 at 11:01:01PM +0100, [EMAIL PROTECTED] wrote: > When I use sendmsg to send descriptors from one process to another using > unix-sockets I need to include at least one byte of normal data for the > descriptors to be send (using the iovec structure). The same code worked
W. R. Stevens, Unix Network Programming (2nd ed), vol 1, p. 389 recommends sending at least a byte anyhow, which allows you to detect EOF. Also see http://www.cs-ipv6.lancs.ac.uk/ipv6/mail-archive/LinuxNetdev/1998-03/0144.html however. I've attached an example that appears to work. Bert #include <sys/socket.h> #include <stdio.h> int sfd(int passfd, int fd, int data) { char cbuf[CMSG_SPACE(sizeof(int))]; struct msghdr mh = { 0 }; struct cmsghdr *cm; int *dp; struct iovec iov; if (fd >= 0) { mh.msg_control = cbuf; mh.msg_controllen = sizeof cbuf; cm = CMSG_FIRSTHDR(&mh); cm->cmsg_len = CMSG_LEN(sizeof(int)); cm->cmsg_level = SOL_SOCKET; cm->cmsg_type = SCM_RIGHTS; dp = CMSG_DATA(cm); *dp = fd; } if (data != 0) { iov.iov_base = &data; iov.iov_len = sizeof data; mh.msg_iov = &iov; mh.msg_iovlen = 1; } return sendmsg(passfd, &mh, 0); } /* Only prepared to rcv one fd per message */ int rcvfd(int passfd, int *data, int *datalen) { char cbuf[CMSG_SPACE(sizeof(int))]; struct msghdr mh = { 0 }; struct cmsghdr *cm; int *dp, ret; struct iovec iov; if (data) { mh.msg_iov = &iov; mh.msg_iovlen = 1; iov.iov_base = &data; iov.iov_len = sizeof(int); } mh.msg_control = cbuf; mh.msg_controllen = sizeof cbuf; cm = CMSG_FIRSTHDR(&mh); cm->cmsg_len = CMSG_LEN(sizeof(int)); cm->cmsg_level = SOL_SOCKET; cm->cmsg_type = SCM_RIGHTS; *datalen = 0; ret = recvmsg(passfd, &mh, 0); if (ret < 0) return ret; if (datalen) *datalen = ret; dp = CMSG_DATA(cm); return *dp; } int main() { int fd[2]; int datalen; socketpair(AF_UNIX, SOCK_DGRAM, 0, fd); printf("Sending returned status: %d\n", sfd(fd[0], 0, 1)); printf("Received fd: %d\n", rcvfd(fd[1], 0, &datalen)); } -- http://www.PowerDNS.com Open source, database driven DNS Software http://netherlabs.nl Open and Closed source services - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
