slirp: Rework internal configuration

The user mode IP stack is currently only minimally configurable /wrt to
its virtual IP addresses. This is unfortunate if some guest has a fixed
idea of which IP addresses to use.

Therefore this patch prepares the stack for fully configurable IP
addresses and masks. The user interface and default addresses remain
untouched in this step, they will be enhanced in the following patch.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/udp.c b/udp.c
index 09eb5ff..7bb7323 100644
--- a/udp.c
+++ b/udp.c
@@ -312,12 +312,14 @@ int udp_output(struct socket *so, struct mbuf *m, struct sockaddr_in *addr)
     struct sockaddr_in saddr, daddr;
 
     saddr = *addr;
-    if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
-        if ((so->so_faddr.s_addr & htonl(0x000000ff)) == htonl(0xff))
-            saddr.sin_addr.s_addr = alias_addr.s_addr;
-        else if (addr->sin_addr.s_addr == loopback_addr.s_addr ||
-                 (ntohl(so->so_faddr.s_addr) & 0xff) != CTL_ALIAS)
-            saddr.sin_addr.s_addr = so->so_faddr.s_addr;
+    if ((so->so_faddr.s_addr & vnetwork_mask.s_addr) == vnetwork_addr.s_addr) {
+        if ((so->so_faddr.s_addr & ~vnetwork_mask.s_addr) ==
+            ~vnetwork_mask.s_addr) {
+            saddr.sin_addr = vhost_addr;
+        } else if (addr->sin_addr.s_addr == loopback_addr.s_addr ||
+                   so->so_faddr.s_addr != vhost_addr.s_addr) {
+            saddr.sin_addr = so->so_faddr;
+        }
     }
     daddr.sin_addr = so->so_laddr;
     daddr.sin_port = so->so_lport;
@@ -647,11 +649,11 @@ struct socket *udp_listen(u_int port, u_int32_t laddr, u_int lport, int flags)
     getsockname(so->s, (struct sockaddr *)&addr, &addrlen);
     so->so_fport = addr.sin_port;
     if (addr.sin_addr.s_addr == 0 ||
-        addr.sin_addr.s_addr == loopback_addr.s_addr)
-        so->so_faddr = alias_addr;
-    else
+        addr.sin_addr.s_addr == loopback_addr.s_addr) {
+        so->so_faddr = vhost_addr;
+    } else {
         so->so_faddr = addr.sin_addr;
-
+    }
     so->so_lport = lport;
     so->so_laddr.s_addr = laddr;
     if (flags != SS_FACCEPTONCE)