int
main(int argc, char *argv[])
{
int sfd, cfd;
ssize_t numRead;
char buf[BUF_SIZE];
sfd = unixBind(SV_SOCK_PATH, SOCK_STREAM);
if (sfd == -1)
errExit("unixBind");
if (listen(sfd, 5) == -1)
errExit("listen");
for (;;) { /* Handle client connections iteratively */
cfd = accept(sfd, NULL, NULL);
if (cfd == -1)
errExit("accept");
/* Transfer data from connected socket to stdout until EOF */
while ((numRead = read(cfd, buf, BUF_SIZE)) > 0)
if (write(STDOUT_FILENO, buf, numRead) != numRead)
fatal("partial/failed write");
if (numRead == -1)
errExit("read");
if (close(cfd) == -1)
errMsg("close");
}
}
int
main(int argc, char *argv[])
{
struct msghdr msgh;
struct iovec iov;
int data, lfd, sfd, fd, opt;
ssize_t nr;
Boolean useDatagramSocket;
union {
struct cmsghdr cmh;
char control[CMSG_SPACE(sizeof(int))];
/* Space large enough to hold an 'int' */
} control_un;
struct cmsghdr *cmhp;
/* Parse command-line arguments */
useDatagramSocket = FALSE;
while ((opt = getopt(argc, argv, "d")) != -1) {
switch (opt) {
case 'd':
useDatagramSocket = TRUE;
break;
default:
usageErr("%s [-d]\n"
" -d use datagram socket\n", argv[0]);
}
}
/* Create socket bound to well-known address */
if (remove(SOCK_PATH) == -1 && errno != ENOENT)
errExit("remove-%s", SOCK_PATH);
if (useDatagramSocket) {
fprintf(stderr, "Receiving via datagram socket\n");
sfd = unixBind(SOCK_PATH, SOCK_DGRAM);
if (sfd == -1)
errExit("unixBind");
} else {
fprintf(stderr, "Receiving via stream socket\n");
lfd = unixListen(SOCK_PATH, 5);
if (lfd == -1)
errExit("unixListen");
sfd = accept(lfd, NULL, 0);
if (sfd == -1)
errExit("accept");
}
/* Set 'control_un' to describe ancillary data that we want to receive */
control_un.cmh.cmsg_len = CMSG_LEN(sizeof(int));
control_un.cmh.cmsg_level = SOL_SOCKET;
control_un.cmh.cmsg_type = SCM_RIGHTS;
/* Set 'msgh' fields to describe 'control_un' */
msgh.msg_control = control_un.control;
msgh.msg_controllen = sizeof(control_un.control);
/* Set fields of 'msgh' to point to buffer used to receive (real)
data read by recvmsg() */
msgh.msg_iov = &iov;
msgh.msg_iovlen = 1;
iov.iov_base = &data;
iov.iov_len = sizeof(int);
msgh.msg_name = NULL; /* We don't need address of peer */
msgh.msg_namelen = 0;
/* Receive real plus ancillary data */
nr = recvmsg(sfd, &msgh, 0);
if (nr == -1)
errExit("recvmsg");
fprintf(stderr, "recvmsg() returned %ld\n", (long) nr);
if (nr > 0)
fprintf(stderr, "Received data = %d\n", data);
/* Get the received file descriptor (which is typically a different
file descriptor number than was used in the sending process) */
cmhp = CMSG_FIRSTHDR(&msgh);
if (cmhp == NULL || cmhp->cmsg_len != CMSG_LEN(sizeof(int)))
fatal("bad cmsg header / message length");
if (cmhp->cmsg_level != SOL_SOCKET)
fatal("cmsg_level != SOL_SOCKET");
if (cmhp->cmsg_type != SCM_RIGHTS)
fatal("cmsg_type != SCM_RIGHTS");
fd = *((int *) CMSG_DATA(cmhp));
fprintf(stderr, "Received fd=%d\n", fd);
/* Having obtained the file descriptor, read the file's contents and
print them on standard output */
for (;;) {
char buf[BUF_SIZE];
ssize_t numRead;
numRead = read(fd, buf, BUF_SIZE);
if (numRead == -1)
errExit("read");
if (numRead == 0)
break;
write(STDOUT_FILENO, buf, numRead);
}
exit(EXIT_SUCCESS);
}
int
main(int argc, char *argv[])
{
struct msghdr msgh;
struct iovec iov;
struct ucred *ucredp, ucred;
int data, lfd, sfd, optval, opt;
ssize_t nr;
Boolean useDatagramSocket;
union {
struct cmsghdr cmh;
char control[CMSG_SPACE(sizeof(struct ucred))];
/* Space large enough to hold a ucred structure */
} control_un;
struct cmsghdr *cmhp;
socklen_t len;
/* Parse command-line arguments */
useDatagramSocket = FALSE;
while ((opt = getopt(argc, argv, "d")) != -1) {
switch (opt) {
case 'd':
useDatagramSocket = TRUE;
break;
default:
usageErr("%s [-d]\n"
" -d use datagram socket\n", argv[0]);
}
}
/* Create socket bound to well-known address */
if (remove(SOCK_PATH) == -1 && errno != ENOENT)
errExit("remove-%s", SOCK_PATH);
if (useDatagramSocket) {
printf("Receiving via datagram socket\n");
sfd = unixBind(SOCK_PATH, SOCK_DGRAM);
if (sfd == -1)
errExit("unixBind");
} else {
printf("Receiving via stream socket\n");
lfd = unixListen(SOCK_PATH, 5);
if (lfd == -1)
errExit("unixListen");
sfd = accept(lfd, NULL, 0);
if (sfd == -1)
errExit("accept");
}
/* We must set the SO_PASSCRED socket option in order to receive
credentials */
optval = 1;
if (setsockopt(sfd, SOL_SOCKET, SO_PASSCRED, &optval, sizeof(optval)) == -1)
errExit("setsockopt");
/* Set 'control_un' to describe ancillary data that we want to receive */
control_un.cmh.cmsg_len = CMSG_LEN(sizeof(struct ucred));
control_un.cmh.cmsg_level = SOL_SOCKET;
control_un.cmh.cmsg_type = SCM_CREDENTIALS;
/* Set 'msgh' fields to describe 'control_un' */
msgh.msg_control = control_un.control;
msgh.msg_controllen = sizeof(control_un.control);
/* Set fields of 'msgh' to point to buffer used to receive (real)
data read by recvmsg() */
msgh.msg_iov = &iov;
msgh.msg_iovlen = 1;
iov.iov_base = &data;
iov.iov_len = sizeof(int);
msgh.msg_name = NULL; /* We don't need address of peer */
msgh.msg_namelen = 0;
/* Receive real plus ancillary data */
nr = recvmsg(sfd, &msgh, 0);
if (nr == -1)
errExit("recvmsg");
printf("recvmsg() returned %ld\n", (long) nr);
if (nr > 0)
printf("Received data = %d\n", data);
/* Extract credentials information from received ancillary data */
cmhp = CMSG_FIRSTHDR(&msgh);
if (cmhp == NULL || cmhp->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
fatal("bad cmsg header / message length");
if (cmhp->cmsg_level != SOL_SOCKET)
fatal("cmsg_level != SOL_SOCKET");
if (cmhp->cmsg_type != SCM_CREDENTIALS)
fatal("cmsg_type != SCM_CREDENTIALS");
ucredp = (struct ucred *) CMSG_DATA(cmhp);
printf("Received credentials pid=%ld, uid=%ld, gid=%ld\n",
(long) ucredp->pid, (long) ucredp->uid, (long) ucredp->gid);
/* The Linux-specific, read-only SO_PEERCRED socket option returns
credential information about the peer, as described in socket(7) */
len = sizeof(struct ucred);
if (getsockopt(sfd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) == -1)
errExit("getsockopt");
printf("Credentials from SO_PEERCRED: pid=%ld, euid=%ld, egid=%ld\n",
(long) ucred.pid, (long) ucred.uid, (long) ucred.gid);
exit(EXIT_SUCCESS);
}
