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fdpassing-keith-packard
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Modified zerowrite to work using SOCK_SEQPACKET. SOCK_STREAM does not work 

because zero length sends only makes sense for packets, not streams.
This commit is contained in:
Nicholas Rishel 2020-06-16 16:17:40 -07:00
parent 9c79e2b92f
commit c3b2188cbb
2 changed files with 28 additions and 13 deletions
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8
fdpass.c
View File

@ -37,10 +37,15 @@ sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd, int *nfdp)
int nfd_passed, nfd; int nfd_passed, nfd;
int i; int i;
int *fd_passed; int *fd_passed;
int type;
int length;
iov.iov_base = buf; iov.iov_base = buf;
iov.iov_len = bufsize; iov.iov_len = bufsize;
length = sizeof( int );
getsockopt (sock, SOL_SOCKET, SO_TYPE, &type, &length);
msg.msg_name = NULL; msg.msg_name = NULL;
msg.msg_namelen = 0; msg.msg_namelen = 0;
msg.msg_iov = &iov; msg.msg_iov = &iov;
@ -52,7 +57,7 @@ sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd, int *nfdp)
perror ("recvmsg"); perror ("recvmsg");
exit(1); exit(1);
} }
if (size > 0 && pass.cmsghdr.cmsg_len > sizeof (struct cmsghdr)) { if ((size > 0 || type == SOCK_SEQPACKET) && pass.cmsghdr.cmsg_len > sizeof (struct cmsghdr)) {
if ((msg.msg_flags & MSG_TRUNC) || if ((msg.msg_flags & MSG_TRUNC) ||
(msg.msg_flags & MSG_CTRUNC)) { (msg.msg_flags & MSG_CTRUNC)) {
fprintf (stderr, "control message truncated"); fprintf (stderr, "control message truncated");
@ -68,7 +73,6 @@ sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd, int *nfdp)
pass.cmsghdr.cmsg_type); pass.cmsghdr.cmsg_type);
exit(1); exit(1);
} }
nfd_passed = (pass.cmsghdr.cmsg_len - sizeof (struct cmsghdr)) / sizeof (int); nfd_passed = (pass.cmsghdr.cmsg_len - sizeof (struct cmsghdr)) / sizeof (int);
fd_passed = (int *) CMSG_DATA(&pass.cmsghdr); fd_passed = (int *) CMSG_DATA(&pass.cmsghdr);

33
zerowrite.c
View File

@ -25,17 +25,28 @@ child(int sock)
ssize_t size; ssize_t size;
sleep(1); sleep(1);
for (;;) { size = sock_fd_read(sock, buf, sizeof(buf), NULL, NULL);
nfd = 1; if (size <= 0) {
size = sock_fd_read(sock, buf, sizeof(buf), &fd, &nfd); printf ("<=0");
if (size <= 0) return;
break;
printf ("read %d nfd %d\n", size, nfd);
if (nfd == 1) {
write(fd, "hello, world\n", 13);
close(fd);
}
} }
printf ("read %d\n", size);
nfd = 1;
size = sock_fd_read(sock, buf, sizeof(buf), &fd, &nfd);
printf ("read %d nfd %d\n", size, nfd);
if (nfd == 1) {
write(fd, "hello, world\n", 13);
close(fd);
}
size = sock_fd_read(sock, buf, sizeof(buf), NULL, NULL);
if (size <= 0) {
printf ("<=0");
return;
}
printf ("read %d\n", size);
} }
void void
@ -60,7 +71,7 @@ main(int argc, char **argv)
int sv[2]; int sv[2];
int pid; int pid;
if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sv) < 0) { if (socketpair(AF_LOCAL, SOCK_SEQPACKET, 0, sv) < 0) {
perror("socketpair"); perror("socketpair");
exit(1); exit(1);
} }