slirp: fix guest network access with darwin host

On Darwin, connect, sendto and friends want the exact size of the sockaddr,
not more (and in particular, not sizeof(struct sockaddr_storaget))

This commit adds the sockaddr_size helper to be used when passing a sockaddr
size to such function, and makes use of it int sendto and connect calls.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: John Arbuckle <programmingkidx@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
diff --git a/ip_icmp.c b/ip_icmp.c
index 917aeae..88cde36 100644
--- a/ip_icmp.c
+++ b/ip_icmp.c
@@ -188,7 +188,7 @@
             sotranslate_out(so, &addr);
 
             if (sendto(so->s, icmp_ping_msg, strlen(icmp_ping_msg), 0,
-                       (struct sockaddr *)&addr, sizeof(addr)) == -1) {
+                       (struct sockaddr *)&addr, sockaddr_size(&addr)) == -1) {
                 DEBUG_MISC((dfd, "icmp_input udp sendto tx errno = %d-%s\n",
                             errno, strerror(errno)));
                 icmp_send_error(m, ICMP_UNREACH, ICMP_UNREACH_NET, 0,
diff --git a/socket.c b/socket.c
index f3b460d..ee76941 100644
--- a/socket.c
+++ b/socket.c
@@ -635,7 +635,7 @@
 
     /* Don't care what port we get */
     ret = sendto(so->s, m->m_data, m->m_len, 0, (struct sockaddr *)&addr,
-                 sizeof(addr));
+                 sockaddr_size(&addr));
     if (ret < 0)
         return -1;
 
diff --git a/socket.h b/socket.h
index 41b54c8..f48370f 100644
--- a/socket.h
+++ b/socket.h
@@ -127,6 +127,18 @@
     return 0;
 }
 
+static inline socklen_t sockaddr_size(struct sockaddr_storage *a)
+{
+    switch (a->ss_family) {
+    case AF_INET:
+        return sizeof(struct sockaddr_in);
+    case AF_INET6:
+        return sizeof(struct sockaddr_in6);
+    default:
+        g_assert_not_reached();
+    }
+}
+
 struct socket *solookup(struct socket **, struct socket *,
                         struct sockaddr_storage *, struct sockaddr_storage *);
 struct socket *socreate(Slirp *);
diff --git a/tcp_subr.c b/tcp_subr.c
index 270e362..2a82c35 100644
--- a/tcp_subr.c
+++ b/tcp_subr.c
@@ -411,7 +411,7 @@
         sotranslate_out(so, &addr);
 
         /* We don't care what port we get */
-        ret = connect(s, (struct sockaddr *)&addr, sizeof(addr));
+        ret = connect(s, (struct sockaddr *)&addr, sockaddr_size(&addr));
 
         /*
          * If it's not in progress, it failed, so we just return 0,