From e5b1e7be64d82b0360af3bed0eaa22ca942be4f4 Mon Sep 17 00:00:00 2001
From: Matt Stancliff <matt@genges.com>
Date: Mon, 3 Mar 2014 10:57:27 -0500
Subject: [PATCH] Bind source address for cluster communication

The first address specified as a bind parameter
(server.bindaddr[0]) gets used as the source IP
for cluster communication.

If no bind address is specified by the user, the
behavior is unchanged.

This patch allows multiple Redis Cluster instances
to communicate when running on the same interface
of the same host.
---
 src/anet.c    | 32 ++++++++++++++++++++++++++++----
 src/anet.h    |  1 +
 src/cluster.c | 11 ++++++++---
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/src/anet.c b/src/anet.c
index 2851318e..91545a0d 100644
--- a/src/anet.c
+++ b/src/anet.c
@@ -234,11 +234,12 @@ static int anetCreateSocket(char *err, int domain) {
 
 #define ANET_CONNECT_NONE 0
 #define ANET_CONNECT_NONBLOCK 1
-static int anetTcpGenericConnect(char *err, char *addr, int port, int flags)
+static int anetTcpGenericConnect(char *err, char *addr, int port,
+                                 char *source_addr, int flags)
 {
     int s = ANET_ERR, rv;
     char portstr[6];  /* strlen("65535") + 1; */
-    struct addrinfo hints, *servinfo, *p;
+    struct addrinfo hints, *servinfo, *bservinfo, *p, *b;
 
     snprintf(portstr,sizeof(portstr),"%d",port);
     memset(&hints,0,sizeof(hints));
@@ -258,6 +259,24 @@ static int anetTcpGenericConnect(char *err, char *addr, int port, int flags)
         if (anetSetReuseAddr(err,s) == ANET_ERR) goto error;
         if (flags & ANET_CONNECT_NONBLOCK && anetNonBlock(err,s) != ANET_OK)
             goto error;
+        if (source_addr) {
+            int bound = 0;
+            /* Using getaddrinfo saves us from self-determining IPv4 vs IPv6 */
+            if ((rv = getaddrinfo(source_addr, NULL, &hints, &bservinfo)) != 0) {
+                anetSetError(err, "%s", gai_strerror(rv));
+                goto end;
+            }
+            for (b = bservinfo; b != NULL; b = b->ai_next) {
+                if (bind(s,b->ai_addr,b->ai_addrlen) != -1) {
+                    bound = 1;
+                    break;
+                }
+            }
+            if (!bound) {
+                anetSetError(err, "bind: %s", strerror(errno));
+                goto end;
+            }
+        }
         if (connect(s,p->ai_addr,p->ai_addrlen) == -1) {
             /* If the socket is non-blocking, it is ok for connect() to
              * return an EINPROGRESS error here. */
@@ -287,12 +306,17 @@ end:
 
 int anetTcpConnect(char *err, char *addr, int port)
 {
-    return anetTcpGenericConnect(err,addr,port,ANET_CONNECT_NONE);
+    return anetTcpGenericConnect(err,addr,port,NULL,ANET_CONNECT_NONE);
 }
 
 int anetTcpNonBlockConnect(char *err, char *addr, int port)
 {
-    return anetTcpGenericConnect(err,addr,port,ANET_CONNECT_NONBLOCK);
+    return anetTcpGenericConnect(err,addr,port,NULL,ANET_CONNECT_NONBLOCK);
+}
+
+int anetTcpNonBlockBindConnect(char *err, char *addr, int port, char *source_addr)
+{
+    return anetTcpGenericConnect(err,addr,port,source_addr,ANET_CONNECT_NONBLOCK);
 }
 
 int anetUnixGenericConnect(char *err, char *path, int flags)
diff --git a/src/anet.h b/src/anet.h
index 3f893be2..c4659cd3 100644
--- a/src/anet.h
+++ b/src/anet.h
@@ -45,6 +45,7 @@
 
 int anetTcpConnect(char *err, char *addr, int port);
 int anetTcpNonBlockConnect(char *err, char *addr, int port);
+int anetTcpNonBlockBindConnect(char *err, char *addr, int port, char *source_addr);
 int anetUnixConnect(char *err, char *path);
 int anetUnixNonBlockConnect(char *err, char *path);
 int anetRead(int fd, char *buf, int count);
diff --git a/src/cluster.c b/src/cluster.c
index afea589e..abe68453 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -2411,9 +2411,14 @@ void clusterCron(void) {
             mstime_t old_ping_sent;
             clusterLink *link;
 
-            fd = anetTcpNonBlockConnect(server.neterr, node->ip,
-                node->port+REDIS_CLUSTER_PORT_INCR);
-            if (fd == -1) continue;
+            fd = anetTcpNonBlockBindConnect(server.neterr, node->ip,
+                node->port+REDIS_CLUSTER_PORT_INCR, server.bindaddr[0]);
+            if (fd == -1) {
+                redisLog(REDIS_DEBUG, "Unable to connect to "
+                    "Cluster Client [%s]:%d", node->ip,
+                    node->port+REDIS_CLUSTER_PORT_INCR);
+                continue;
+            }
             link = createClusterLink(node);
             link->fd = fd;
             node->link = link;