slirp: Factorizing address translation

This patch factorizes some duplicate code into a new function,
sotranslate_out(). This function perform the address translation when a
packet is transmitted to the host network. If the packet is destinated
to the host, the loopback address is used, and if the packet is
destinated to the virtual DNS, the real DNS address is used. This code
is just a copy of the existent, but factorized and ready to manage the
IPv6 case.

On the same model, the major part of udp_output() code is moved into a
new sotranslate_in(). This function is directly used in sorecvfrom(),
like sotranslate_out() in sosendto().
udp_output() becoming useless, it is removed and udp_output2() is
renamed into udp_output(). This adds consistency with the udp6_output()
function introduced by further patches.

Lastly, this factorizes some duplicate code into sotranslate_accept(), which
performs the address translation when a connection is established on the host
for port forwarding: if it comes from localhost, the host virtual address is
used instead.

This prepares for IPv6 support.

Signed-off-by: Guillaume Subiron <maethor@subiron.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

1 files changed, 92 insertions, 20 deletions

diff --git a/slirp/socket.c b/slirp/socket.c
index bf603c9185..d1034fb536 100644
--- a/slirp/socket.c
+++ b/slirp/socket.c
@@ -438,6 +438,7 @@ void
 sorecvfrom(struct socket *so)
 {
 	struct sockaddr_storage addr;
+	struct sockaddr_storage saddr, daddr;
 	socklen_t addrlen = sizeof(struct sockaddr_storage);
 
 	DEBUG_CALL("sorecvfrom");
@@ -525,11 +526,17 @@ sorecvfrom(struct socket *so)
 
 	    /*
 	     * If this packet was destined for CTL_ADDR,
-	     * make it look like that's where it came from, done by udp_output
+	     * make it look like that's where it came from
 	     */
+	    saddr = addr;
+	    sotranslate_in(so, &saddr);
+	    daddr = so->lhost.ss;
+
 	    switch (so->so_ffamily) {
 	    case AF_INET:
-	        udp_output(so, m, (struct sockaddr_in *) &addr);
+	        udp_output(so, m, (struct sockaddr_in *) &saddr,
+	                   (struct sockaddr_in *) &daddr,
+	                   so->so_iptos);
 	        break;
 	    default:
 	        break;
@@ -544,33 +551,20 @@ sorecvfrom(struct socket *so)
 int
 sosendto(struct socket *so, struct mbuf *m)
 {
-	Slirp *slirp = so->slirp;
 	int ret;
-	struct sockaddr_in addr;
+	struct sockaddr_storage addr;
 
 	DEBUG_CALL("sosendto");
 	DEBUG_ARG("so = %p", so);
 	DEBUG_ARG("m = %p", m);
 
-        addr.sin_family = AF_INET;
-	if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
-	    slirp->vnetwork_addr.s_addr) {
-	  /* It's an alias */
-	  if (so->so_faddr.s_addr == slirp->vnameserver_addr.s_addr) {
-	    if (get_dns_addr(&addr.sin_addr) < 0)
-	      addr.sin_addr = loopback_addr;
-	  } else {
-	    addr.sin_addr = loopback_addr;
-	  }
-	} else
-	  addr.sin_addr = so->so_faddr;
-	addr.sin_port = so->so_fport;
-
-	DEBUG_MISC((dfd, " sendto()ing, addr.sin_port=%d, addr.sin_addr.s_addr=%.16s\n", ntohs(addr.sin_port), inet_ntoa(addr.sin_addr)));
+	addr = so->fhost.ss;
+	DEBUG_CALL(" sendto()ing)");
+	sotranslate_out(so, &addr);
 
 	/* Don't care what port we get */
 	ret = sendto(so->s, m->m_data, m->m_len, 0,
-		     (struct sockaddr *)&addr, sizeof (struct sockaddr));
+		     (struct sockaddr *)&addr, sizeof(addr));
 	if (ret < 0)
 		return -1;
 
@@ -726,3 +720,81 @@ sofwdrain(struct socket *so)
 	else
 		sofcantsendmore(so);
 }
+
+/*
+ * Translate addr in host addr when it is a virtual address
+ */
+void sotranslate_out(struct socket *so, struct sockaddr_storage *addr)
+{
+    Slirp *slirp = so->slirp;
+    struct sockaddr_in *sin = (struct sockaddr_in *)addr;
+
+    switch (addr->ss_family) {
+    case AF_INET:
+        if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
+                slirp->vnetwork_addr.s_addr) {
+            /* It's an alias */
+            if (so->so_faddr.s_addr == slirp->vnameserver_addr.s_addr) {
+                if (get_dns_addr(&sin->sin_addr) < 0) {
+                    sin->sin_addr = loopback_addr;
+                }
+            } else {
+                sin->sin_addr = loopback_addr;
+            }
+        }
+
+        DEBUG_MISC((dfd, " addr.sin_port=%d, "
+            "addr.sin_addr.s_addr=%.16s\n",
+            ntohs(sin->sin_port), inet_ntoa(sin->sin_addr)));
+        break;
+
+    default:
+        break;
+    }
+}
+
+void sotranslate_in(struct socket *so, struct sockaddr_storage *addr)
+{
+    Slirp *slirp = so->slirp;
+    struct sockaddr_in *sin = (struct sockaddr_in *)addr;
+
+    switch (addr->ss_family) {
+    case AF_INET:
+        if ((so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
+            slirp->vnetwork_addr.s_addr) {
+            uint32_t inv_mask = ~slirp->vnetwork_mask.s_addr;
+
+            if ((so->so_faddr.s_addr & inv_mask) == inv_mask) {
+                sin->sin_addr = slirp->vhost_addr;
+            } else if (sin->sin_addr.s_addr == loopback_addr.s_addr ||
+                       so->so_faddr.s_addr != slirp->vhost_addr.s_addr) {
+                sin->sin_addr = so->so_faddr;
+            }
+        }
+        break;
+
+    default:
+        break;
+    }
+}
+
+/*
+ * Translate connections from localhost to the real hostname
+ */
+void sotranslate_accept(struct socket *so)
+{
+    Slirp *slirp = so->slirp;
+
+    switch (so->so_ffamily) {
+    case AF_INET:
+        if (so->so_faddr.s_addr == INADDR_ANY ||
+            (so->so_faddr.s_addr & loopback_mask) ==
+            (loopback_addr.s_addr & loopback_mask)) {
+           so->so_faddr = slirp->vhost_addr;
+        }
+        break;
+
+    default:
+        break;
+    }
+}