TCP/IP Port Forwarding + Patch

[Oleksandr Shneyder <o.shneyder@xxxxxxxxxxxxx>]

Hello,
here is a patch to fix problem with port forwarding.

Problem description:

//forward port 9080
ssh_forward_listen(session, NULL, 9080, NULL);
//forward port 9090
ssh_forward_listen(session, NULL, 9090, NULL);
//accept connections
while(1){
ssh_channel channel = ssh_forward_accept(session, 1000);
//channel created, but we don't know if it from port 9080 or 9090 !!!
}

Solution - use function, that return destination port (see patch)

//forward port 9080
ssh_forward_listen(session, NULL, 9080, NULL);
//forward port 9090
ssh_forward_listen(session, NULL, 9090, NULL);
//accept connections
while(1){
int port;
ssh_channel channel = ssh_forward_accept_ex(session, 1000, &port);
fprintf(stderr, "forwarding channel from port %d\n", port);
}

As we need multiply port forwarding in our project (X2Go), please accept
my patch or suggest your own solution to solve this problem. We will
take care about patching old versions of libssh used by Debian and
possible other Linux distributions.

regards,
Alex
-- 
----------------------------------------------------
Oleksandr Shneyder  | Email: o.shneyder@xxxxxxxxxxxxx
phoca GmbH          | Tel. : 0911 - 14870374 0
Bräuhausgasse 9     | Fax. : 0911 - 14870374 9
D-82205 Gilching    | Mobil: 0163 - 49 64 461

Geschäftsführung:
Dipl.-Inf. Oleksandr Shneyder

Amtsgericht München | http://www.phoca-gmbh.de
HRB 196 658         | http://www.x2go.org
USt-IdNr.: DE281977973
----------------------------------------------------

diff --git a/include/libssh/libssh.h b/include/libssh/libssh.h
index 46aafae..411a562 100644
--- a/include/libssh/libssh.h
+++ b/include/libssh/libssh.h
@@ -406,6 +406,7 @@ LIBSSH_API void ssh_disconnect(ssh_session session);
 LIBSSH_API char *ssh_dirname (const char *path);
 LIBSSH_API int ssh_finalize(void);
 LIBSSH_API ssh_channel ssh_forward_accept(ssh_session session, int timeout_ms);
+LIBSSH_API ssh_channel ssh_forward_accept_ex(ssh_session session, int timeout_ms, int *destination_port);
 LIBSSH_API int ssh_forward_cancel(ssh_session session, const char *address, int port);
 LIBSSH_API int ssh_forward_listen(ssh_session session, const char *address, int port, int *bound_port);
 LIBSSH_API void ssh_free(ssh_session session);
diff --git a/src/channels.c b/src/channels.c
index 0547889..48e7218 100644
--- a/src/channels.c
+++ b/src/channels.c
@@ -1989,7 +1989,7 @@ error:
 }
 
 static ssh_channel ssh_channel_accept(ssh_session session, int channeltype,
-    int timeout_ms) {
+    int timeout_ms, int *destination_port) {
 #ifndef _WIN32
   static const struct timespec ts = {
     .tv_sec = 0,
@@ -2016,6 +2016,10 @@ static ssh_channel ssh_channel_accept(ssh_session session, int channeltype,
             ssh_message_subtype(msg) == channeltype) {
           ssh_list_remove(session->ssh_message_list, iterator);
           channel = ssh_message_channel_request_open_reply_accept(msg);
+          if(destination_port) {
+            *destination_port=msg->channel_request_open.destination_port;
+          }
+
           ssh_message_free(msg);
           return channel;
         }
@@ -2046,7 +2050,7 @@ static ssh_channel ssh_channel_accept(ssh_session session, int channeltype,
  *                      the server.
  */
 ssh_channel ssh_channel_accept_x11(ssh_channel channel, int timeout_ms) {
-  return ssh_channel_accept(channel->session, SSH_CHANNEL_X11, timeout_ms);
+  return ssh_channel_accept(channel->session, SSH_CHANNEL_X11, timeout_ms, NULL);
 }
 
 /**
@@ -2300,7 +2304,23 @@ error:
  *         the server
  */
 ssh_channel ssh_forward_accept(ssh_session session, int timeout_ms) {
-  return ssh_channel_accept(session, SSH_CHANNEL_FORWARDED_TCPIP, timeout_ms);
+  return ssh_channel_accept(session, SSH_CHANNEL_FORWARDED_TCPIP, timeout_ms, NULL);
+}
+
+/**
+ * @brief Accept an incoming TCP/IP forwarding channel and get information
+ * about incomming connection
+ * @param[in]  session    The ssh session to use.
+ *
+ * @param[in]  timeout_ms A timeout in milliseconds.
+ *
+ * @param[in]  destination_port A pointer to destination port or NULL.
+ *
+ * @return Newly created channel, or NULL if no incoming channel request from
+ *         the server
+ */
+ssh_channel ssh_forward_accept_ex(ssh_session session, int timeout_ms, int* destination_port) {
+  return ssh_channel_accept(session, SSH_CHANNEL_FORWARDED_TCPIP, timeout_ms, destination_port);
 }
 
 /**

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