slirp_add_host*fwd: Ensure all error paths set errno

Debugging bind/listen failures without errno can get painful.

Signed-off-by: Doug Evans <dje@google.com>

4 files changed, 14 insertions, 2 deletions

diff --git a/src/slirp.c b/src/slirp.c
index 40d3873..fcaa179 100644
--- a/src/slirp.c
+++ b/src/slirp.c
@@ -1175,8 +1175,10 @@ int slirp_add_hostxfwd(Slirp *slirp,
     if (gaddr->sa_family == AF_INET) {
         const struct sockaddr_in *gaddr_in = (const struct sockaddr_in *) gaddr;
 
-        if (gaddrlen < sizeof(struct sockaddr_in))
+        if (gaddrlen < sizeof(struct sockaddr_in)) {
+            errno = EINVAL;
             return -1;
+        }
 
         if (!gaddr_in->sin_addr.s_addr) {
             gdhcp_addr = *gaddr_in;
@@ -1187,8 +1189,10 @@ int slirp_add_hostxfwd(Slirp *slirp,
     } else {
         const struct sockaddr_in6 *gaddr_in6 = (const struct sockaddr_in6 *) gaddr;
 
-        if (gaddrlen < sizeof(struct sockaddr_in6))
+        if (gaddrlen < sizeof(struct sockaddr_in6)) {
+            errno = EINVAL;
             return -1;
+        }
 
         if (in6_zero(&gaddr_in6->sin6_addr)) {
             /*
@@ -1196,6 +1200,7 @@ int slirp_add_hostxfwd(Slirp *slirp,
              * we can't translate "addr-any" to the guest. Instead, for now,
              * reject it.
              */
+            errno = EINVAL;
             return -1;
         }
     }
diff --git a/src/socket.c b/src/socket.c
index 679ac4f..9166d83 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -735,6 +735,7 @@ int sosendto(struct socket *so, struct mbuf *m)
 
 /*
  * Listen for incoming TCP connections
+ * On failure errno contains the reason.
  */
 struct socket *tcpx_listen(Slirp *slirp,
                            const struct sockaddr *haddr, socklen_t haddrlen,
diff --git a/src/udp.c b/src/udp.c
index 37f13ca..bb65ecf 100644
--- a/src/udp.c
+++ b/src/udp.c
@@ -360,18 +360,23 @@ struct socket *udpx_listen(Slirp *slirp,
 {
     struct socket *so;
     socklen_t addrlen;
+    int save_errno;
 
     so = socreate(slirp);
     so->s = slirp_socket(haddr->sa_family, SOCK_DGRAM, 0);
     if (so->s < 0) {
+        save_errno = errno;
         sofree(so);
+        errno = save_errno;
         return NULL;
     }
     so->so_expire = curtime + SO_EXPIRE;
     insque(so, &slirp->udb);
 
     if (bind(so->s, haddr, haddrlen) < 0) {
+        save_errno = errno;
         udp_detach(so);
+        errno = save_errno;
         return NULL;
     }
     slirp_socket_set_fast_reuse(so->s);
diff --git a/src/util.c b/src/util.c
index 67ef667..e6bccbe 100644
--- a/src/util.c
+++ b/src/util.c
@@ -71,6 +71,7 @@ static void slirp_set_cloexec(int fd)
 
 /*
  * Opens a socket with FD_CLOEXEC set
+ * On failure errno contains the reason.
  */
 int slirp_socket(int domain, int type, int protocol)
 {