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slirp: move socket pair creation in helper function

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Originally, the patch was fixing a bunch of issues, but Peter beat me
to it with earlier commit "slirp: fork_exec(): create and connect
child socket before fork()".

Factor out socket pair creation, to simplify the fork_exec() code.
Use the name socketpair_with_oob() since the code is actually similar
to what socketpair() would do, except that it uses TCP sockets, for
SLIRP to be able to call send with MSG_OOB (since SO_OOBINLINE is set,
this could probably be faked instead on regular unix sockets though).

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
This commit is contained in:
Marc-André Lureau 2018-11-14 16:36:03 +04:00 committed by Samuel Thibault
parent 9a50b0e0b8
commit 7f5140929b
1 changed files with 71 additions and 71 deletions
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142
slirp/misc.c
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@ -73,85 +73,92 @@ fork_exec(struct socket *so, const char *ex)
#else
/*
* XXX This is ugly
* We create and bind a socket, then fork off to another
* process, which connects to this socket, after which we
* exec the wanted program. If something (strange) happens,
* the accept() call could block us forever.
*/
static int
slirp_socketpair_with_oob(int sv[2])
{
struct sockaddr_in addr = {
.sin_family = AF_INET,
.sin_port = 0,
.sin_addr.s_addr = INADDR_ANY,
};
socklen_t addrlen = sizeof(addr);
int ret, s;
sv[1] = -1;
s = qemu_socket(AF_INET, SOCK_STREAM, 0);
if (s < 0 || bind(s, (struct sockaddr *)&addr, addrlen) < 0 ||
listen(s, 1) < 0 ||
getsockname(s, (struct sockaddr *)&addr, &addrlen) < 0) {
goto err;
}
sv[1] = qemu_socket(AF_INET, SOCK_STREAM, 0);
if (sv[1] < 0) {
goto err;
}
/*
* This connect won't block because we've already listen()ed on
* the server end (even though we won't accept() the connection
* until later on).
*/
do {
ret = connect(sv[1], (struct sockaddr *)&addr, addrlen);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
goto err;
}
do {
sv[0] = accept(s, (struct sockaddr *)&addr, &addrlen);
} while (sv[0] < 0 && errno == EINTR);
if (sv[0] < 0) {
goto err;
}
closesocket(s);
return 0;
err:
error_report("Error: slirp_socketpair(): %s", strerror(errno));
if (s >= 0) {
closesocket(s);
}
if (sv[1] >= 0) {
closesocket(sv[1]);
}
return -1;
}
int
fork_exec(struct socket *so, const char *ex)
{
int s, cs;
struct sockaddr_in addr, csaddr;
socklen_t addrlen = sizeof(addr);
socklen_t csaddrlen = sizeof(csaddr);
int opt;
char **argv;
int ret;
int opt, c, sp[2];
pid_t pid;
DEBUG_CALL("fork_exec");
DEBUG_ARG("so = %p", so);
DEBUG_ARG("ex = %p", ex);
addr.sin_family = AF_INET;
addr.sin_port = 0;
addr.sin_addr.s_addr = INADDR_ANY;
s = qemu_socket(AF_INET, SOCK_STREAM, 0);
if (s < 0 || bind(s, (struct sockaddr *)&addr, addrlen) < 0 ||
listen(s, 1) < 0) {
error_report("Error: inet socket: %s", strerror(errno));
if (s >= 0) {
closesocket(s);
}
if (slirp_socketpair_with_oob(sp) < 0) {
return 0;
}
if (getsockname(s, (struct sockaddr *)&csaddr, &csaddrlen) < 0) {
closesocket(s);
return 0;
}
cs = qemu_socket(AF_INET, SOCK_STREAM, 0);
if (cs < 0) {
closesocket(s);
return 0;
}
csaddr.sin_addr = loopback_addr;
/*
* This connect won't block because we've already listen()ed on
* the server end (even though we won't accept() the connection
* until later on).
*/
do {
ret = connect(cs, (struct sockaddr *)&csaddr, csaddrlen);
} while (ret < 0 && errno == EINTR);
if (ret < 0) {
closesocket(s);
closesocket(cs);
return 0;
}
pid = fork();
switch(pid) {
case -1:
error_report("Error: fork failed: %s", strerror(errno));
closesocket(cs);
close(s);
closesocket(sp[0]);
closesocket(sp[1]);
return 0;
case 0:
setsid();
/* Set the DISPLAY */
close(s);
dup2(cs, 0);
dup2(cs, 1);
dup2(cs, 2);
for (s = getdtablesize() - 1; s >= 3; s--)
close(s);
setsid();
dup2(sp[1], 0);
dup2(sp[1], 1);
dup2(sp[1], 2);
for (c = getdtablesize() - 1; c >= 3; c--)
close(c);
argv = g_strsplit(ex, " ", -1);
execvp(argv[0], (char **)argv);
@ -163,19 +170,12 @@ fork_exec(struct socket *so, const char *ex)
exit(1);
default:
so->s = sp[0];
closesocket(sp[1]);
qemu_add_child_watch(pid);
closesocket(cs);
/*
* This should never block, because we already connect()ed
* on the child end before we forked.
*/
do {
so->s = accept(s, (struct sockaddr *)&addr, &addrlen);
} while (so->s < 0 && errno == EINTR);
closesocket(s);
socket_set_fast_reuse(so->s);
opt = 1;
qemu_setsockopt(so->s, SOL_SOCKET, SO_OOBINLINE, &opt, sizeof(int));
socket_set_fast_reuse(so->s);
opt = 1;
qemu_setsockopt(so->s, SOL_SOCKET, SO_OOBINLINE, &opt, sizeof(int));
qemu_set_nonblock(so->s);
return 1;
}