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qemu/slirp/misc.c
Peter Maydell 5c75f3adbb slirp: fork_exec(): create and connect child socket before fork() 
Currently fork_exec() fork()s, and then creates and connects the
child socket which it uses for communication with the parent in
the child process. This is awkward because the child has no
mechanism to report failure back to the parent, which might end
up blocked forever in accept(). The child code also has an issue
pointed out by Coverity (CID 1005727), where if the qemu_socket()
call fails it will pass -1 as a file descriptor to connect().

Fix these issues by moving the creation of the child's end of
the socket to before the fork(), where we are in a position to
handle a possible failure.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
2018-11-10 15:07:53 +01:00

309 lines
8.9 KiB
C
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/*
* Copyright (c) 1995 Danny Gasparovski.
*
* Please read the file COPYRIGHT for the
* terms and conditions of the copyright.
*/
#include "qemu/osdep.h"
#include "slirp.h"
#include "libslirp.h"
#include "monitor/monitor.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#ifdef DEBUG
int slirp_debug = DBG_CALL|DBG_MISC|DBG_ERROR;
#endif
inline void
insque(void *a, void *b)
{
register struct quehead *element = (struct quehead *) a;
register struct quehead *head = (struct quehead *) b;
element->qh_link = head->qh_link;
head->qh_link = (struct quehead *)element;
element->qh_rlink = (struct quehead *)head;
((struct quehead *)(element->qh_link))->qh_rlink
= (struct quehead *)element;
}
inline void
remque(void *a)
{
register struct quehead *element = (struct quehead *) a;
((struct quehead *)(element->qh_link))->qh_rlink = element->qh_rlink;
((struct quehead *)(element->qh_rlink))->qh_link = element->qh_link;
element->qh_rlink = NULL;
}
int add_exec(struct ex_list **ex_ptr, int do_pty, char *exec,
struct in_addr addr, int port)
{
struct ex_list *tmp_ptr;
/* First, check if the port is "bound" */
for (tmp_ptr = *ex_ptr; tmp_ptr; tmp_ptr = tmp_ptr->ex_next) {
if (port == tmp_ptr->ex_fport &&
addr.s_addr == tmp_ptr->ex_addr.s_addr)
return -1;
}
tmp_ptr = *ex_ptr;
*ex_ptr = g_new(struct ex_list, 1);
(*ex_ptr)->ex_fport = port;
(*ex_ptr)->ex_addr = addr;
(*ex_ptr)->ex_pty = do_pty;
(*ex_ptr)->ex_exec = (do_pty == 3) ? exec : g_strdup(exec);
(*ex_ptr)->ex_next = tmp_ptr;
return 0;
}
#ifdef _WIN32
int
fork_exec(struct socket *so, const char *ex, int do_pty)
{
/* not implemented */
return 0;
}
#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.
*
* do_pty = 0 Fork/exec inetd style
* do_pty = 1 Fork/exec using slirp.telnetd
* do_ptr = 2 Fork/exec using pty
*/
int
fork_exec(struct socket *so, const char *ex, int do_pty)
{
int s, cs;
struct sockaddr_in addr, csaddr;
socklen_t addrlen = sizeof(addr);
socklen_t csaddrlen = sizeof(csaddr);
int opt;
const char *argv[256];
/* don't want to clobber the original */
char *bptr;
const char *curarg;
int c, i, ret;
pid_t pid;
DEBUG_CALL("fork_exec");
DEBUG_ARG("so = %p", so);
DEBUG_ARG("ex = %p", ex);
DEBUG_ARG("do_pty = %x", do_pty);
if (do_pty == 2) {
return 0;
} else {
addr.sin_family = AF_INET;
addr.sin_port = 0;
addr.sin_addr.s_addr = INADDR_ANY;
if ((s = qemu_socket(AF_INET, SOCK_STREAM, 0)) < 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);
}
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);
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);
i = 0;
bptr = g_strdup(ex); /* No need to free() this */
if (do_pty == 1) {
/* Setup "slirp.telnetd -x" */
argv[i++] = "slirp.telnetd";
argv[i++] = "-x";
argv[i++] = bptr;
} else
do {
/* Change the string into argv[] */
curarg = bptr;
while (*bptr != ' ' && *bptr != (char)0)
bptr++;
c = *bptr;
*bptr++ = (char)0;
argv[i++] = g_strdup(curarg);
} while (c);
argv[i] = NULL;
execvp(argv[0], (char **)argv);
/* Ooops, failed, let's tell the user why */
fprintf(stderr, "Error: execvp of %s failed: %s\n",
argv[0], strerror(errno));
close(0); close(1); close(2); /* XXX */
exit(1);
default:
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));
qemu_set_nonblock(so->s);
/* Append the telnet options now */
if (so->so_m != NULL && do_pty == 1) {
sbappend(so, so->so_m);
so->so_m = NULL;
}
return 1;
}
}
#endif
void slirp_connection_info(Slirp *slirp, Monitor *mon)
{
const char * const tcpstates[] = {
[TCPS_CLOSED] = "CLOSED",
[TCPS_LISTEN] = "LISTEN",
[TCPS_SYN_SENT] = "SYN_SENT",
[TCPS_SYN_RECEIVED] = "SYN_RCVD",
[TCPS_ESTABLISHED] = "ESTABLISHED",
[TCPS_CLOSE_WAIT] = "CLOSE_WAIT",
[TCPS_FIN_WAIT_1] = "FIN_WAIT_1",
[TCPS_CLOSING] = "CLOSING",
[TCPS_LAST_ACK] = "LAST_ACK",
[TCPS_FIN_WAIT_2] = "FIN_WAIT_2",
[TCPS_TIME_WAIT] = "TIME_WAIT",
};
struct in_addr dst_addr;
struct sockaddr_in src;
socklen_t src_len;
uint16_t dst_port;
struct socket *so;
const char *state;
char buf[20];
monitor_printf(mon, " Protocol[State] FD Source Address Port "
"Dest. Address Port RecvQ SendQ\n");
for (so = slirp->tcb.so_next; so != &slirp->tcb; so = so->so_next) {
if (so->so_state & SS_HOSTFWD) {
state = "HOST_FORWARD";
} else if (so->so_tcpcb) {
state = tcpstates[so->so_tcpcb->t_state];
} else {
state = "NONE";
}
if (so->so_state & (SS_HOSTFWD | SS_INCOMING)) {
src_len = sizeof(src);
getsockname(so->s, (struct sockaddr *)&src, &src_len);
dst_addr = so->so_laddr;
dst_port = so->so_lport;
} else {
src.sin_addr = so->so_laddr;
src.sin_port = so->so_lport;
dst_addr = so->so_faddr;
dst_port = so->so_fport;
}
snprintf(buf, sizeof(buf), " TCP[%s]", state);
monitor_printf(mon, "%-19s %3d %15s %5d ", buf, so->s,
src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*",
ntohs(src.sin_port));
monitor_printf(mon, "%15s %5d %5d %5d\n",
inet_ntoa(dst_addr), ntohs(dst_port),
so->so_rcv.sb_cc, so->so_snd.sb_cc);
}
for (so = slirp->udb.so_next; so != &slirp->udb; so = so->so_next) {
if (so->so_state & SS_HOSTFWD) {
snprintf(buf, sizeof(buf), " UDP[HOST_FORWARD]");
src_len = sizeof(src);
getsockname(so->s, (struct sockaddr *)&src, &src_len);
dst_addr = so->so_laddr;
dst_port = so->so_lport;
} else {
snprintf(buf, sizeof(buf), " UDP[%d sec]",
(so->so_expire - curtime) / 1000);
src.sin_addr = so->so_laddr;
src.sin_port = so->so_lport;
dst_addr = so->so_faddr;
dst_port = so->so_fport;
}
monitor_printf(mon, "%-19s %3d %15s %5d ", buf, so->s,
src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*",
ntohs(src.sin_port));
monitor_printf(mon, "%15s %5d %5d %5d\n",
inet_ntoa(dst_addr), ntohs(dst_port),
so->so_rcv.sb_cc, so->so_snd.sb_cc);
}
for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so->so_next) {
snprintf(buf, sizeof(buf), " ICMP[%d sec]",
(so->so_expire - curtime) / 1000);
src.sin_addr = so->so_laddr;
dst_addr = so->so_faddr;
monitor_printf(mon, "%-19s %3d %15s - ", buf, so->s,
src.sin_addr.s_addr ? inet_ntoa(src.sin_addr) : "*");
monitor_printf(mon, "%15s - %5d %5d\n", inet_ntoa(dst_addr),
so->so_rcv.sb_cc, so->so_snd.sb_cc);
}
}
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