From 92038286e8c047966f779e8d7eefa6d2786bfa43 Mon Sep 17 00:00:00 2001
From: oranagra <oran@redislabs.com>
Date: Sun, 21 Aug 2016 20:39:15 +0300
Subject: [PATCH] fix tcp binding when IPv6 is unsupported

---
 src/anet.c   |  2 +-
 src/server.c | 22 +++++++++++++---------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/anet.c b/src/anet.c
index 1728f3eb..ef1711d0 100644
--- a/src/anet.c
+++ b/src/anet.c
@@ -486,7 +486,7 @@ static int _anetTcpServer(char *err, int port, char *bindaddr, int af, int backl
         goto end;
     }
     if (p == NULL) {
-        anetSetError(err, "unable to bind socket");
+        anetSetError(err, "unable to bind socket, errno: %d", errno);
         goto error;
     }
 
diff --git a/src/server.c b/src/server.c
index a7758259..fe8364d0 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1636,6 +1636,7 @@ int listenToPort(int port, int *fds, int *count) {
     if (server.bindaddr_count == 0) server.bindaddr[0] = NULL;
     for (j = 0; j < server.bindaddr_count || j == 0; j++) {
         if (server.bindaddr[j] == NULL) {
+            int unsupported = 0;
             /* Bind * for both IPv6 and IPv4, we enter here only if
              * server.bindaddr_count == 0. */
             fds[*count] = anetTcp6Server(server.neterr,port,NULL,
@@ -1643,19 +1644,22 @@ int listenToPort(int port, int *fds, int *count) {
             if (fds[*count] != ANET_ERR) {
                 anetNonBlock(NULL,fds[*count]);
                 (*count)++;
+            } else if (errno == EAFNOSUPPORT)
+                unsupported++;
 
-                /* Bind the IPv4 address as well. */
-                fds[*count] = anetTcpServer(server.neterr,port,NULL,
-                    server.tcp_backlog);
-                if (fds[*count] != ANET_ERR) {
-                    anetNonBlock(NULL,fds[*count]);
-                    (*count)++;
-                }
-            }
+            /* Bind the IPv4 address as well. */
+            fds[*count] = anetTcpServer(server.neterr,port,NULL,
+                server.tcp_backlog);
+            if (fds[*count] != ANET_ERR) {
+                anetNonBlock(NULL,fds[*count]);
+                (*count)++;
+            } else if (errno == EAFNOSUPPORT)
+                unsupported++;
             /* Exit the loop if we were able to bind * on IPv4 and IPv6,
+             * or if one is unsupported by th OS.
              * otherwise fds[*count] will be ANET_ERR and we'll print an
              * error and return to the caller with an error. */
-            if (*count == 2) break;
+            if (*count + unsupported == 2) break;
         } else if (strchr(server.bindaddr[j],':')) {
             /* Bind IPv6 address. */
             fds[*count] = anetTcp6Server(server.neterr,port,server.bindaddr[j],