make user networking hostfwd work with restrict=y

This patch allows the hostfwd option to override the restrict=y setting in the user network stack, as explicitly stated in the documentation on the restrict option:

restrict=on|off
If this option is enabled, the guest will be isolated, i.e. it will not be able to contact the host and no guest IP packets will be routed over the host to the outside. This option does not affect any explicitly set forwarding rules.

Qemu bug tracker:
https://bugs.launchpad.net/qemu/+bug/829455

diff -aur qemu-kvm-0.15.0+noroms/slirp/tcp_input.c qemu-kvm-0.15.0+noromsnew/slirp/tcp_input.c

slirp/tcp_input.c +17 -11

@@ -316,16 +316,6 @@
  	m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
  	m->m_len  -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
 
-    if (slirp->restricted) {
-        for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
-            if (ex_ptr->ex_fport == ti->ti_dport&&
-                ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
-                break;
-            }
-        }
-        if (!ex_ptr)
-            goto drop;
-    }
  	/*
  	 * Locate pcb for segment.
  	 */

@@ -354,7 +344,23 @@
  	 * the only flag set, then create a session, mark it
  	 * as if it was LISTENING, and continue...
  	 */
-        if (so == NULL) {
+    if (so == NULL) {
+        if (slirp->restricted) {
+            /* Any hostfwds will have an existing socket, so we only get here
+             * for non-hostfwd connections. These should be dropped, unless it
+             * happens to be a guestfwd.
+             */
+            for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
+                if (ex_ptr->ex_fport == ti->ti_dport&&
+                    ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
+                    break;
+                }
+            }
+            if (!ex_ptr) {
+                goto dropwithreset;
+            }
+        }
+
  	  if ((tiflags&  (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
  	    goto dropwithreset;
 

Signed-off-by Gertjan Halkes<[email protected]>

Please submit against qemu.git master with a Signed-off-by.

Quoted 1 line · Anthony Liguori

Please submit against qemu.git master with a Signed-off-by.

Ok, here goes:

This patch allows the hostfwd option to override the restrict=y setting in the user network stack, as explicitly stated in the documentation on the restrict option:

    restrict=on|off
        If this option is enabled, the guest will be isolated, i.e. it will not be able to contact the host and no guest IP packets will be routed over the host to the outside. This option does not affect any explicitly set forwarding rules.

Qemu bug tracker:
https://bugs.launchpad.net/qemu/+bug/829455

Signed-off-by Gertjan Halkes <[email protected]>

---
 slirp/tcp_input.c |   28 +++++++++++++++++-----------

 1 files changed, 17 insertions(+), 11 deletions(-)

slirp/tcp_input.c +17 -12

index 942aaf4..ed09c27 100644
@@ -316,16 +316,6 @@ tcp_input(struct mbuf *m, int iphlen, struct socket *inso)
        m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
        m->m_len  -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
 
-    if (slirp->restricted) {
-        for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
-            if (ex_ptr->ex_fport == ti->ti_dport &&
-                ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
-                break;
-            }
-        }
-        if (!ex_ptr)
-            goto drop;
-    }
        /*
         * Locate pcb for segment.
         */

@@ -354,7 +344,23 @@ findso:
         * the only flag set, then create a session, mark it
         * as if it was LISTENING, and continue...
         */
-        if (so == NULL) {
+    if (so == NULL) {
+        if (slirp->restricted) {
+            /* Any hostfwds will have an existing socket, so we only get here
+             * for non-hostfwd connections. These should be dropped, unless it
+             * happens to be a guestfwd.
+             */
+            for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
+                if (ex_ptr->ex_fport == ti->ti_dport &&
+                    ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
+                    break;
+                }
+            }
+            if (!ex_ptr) {
+                goto dropwithreset;
+            }
+        }
+
          if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
            goto dropwithreset;
 
--

1.7.1