From c3846becae5528e2987865ec1a5ef2cdeca3dadd Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 4 Dec 2014 10:54:31 +0100
Subject: [PATCH] Check that tcp-backlog is matched by
 /proc/sys/net/core/somaxconn.

---
 src/config.h |  1 +
 src/redis.c  | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/src/config.h b/src/config.h
index 57d07599..1f2919ed 100644
--- a/src/config.h
+++ b/src/config.h
@@ -48,6 +48,7 @@
 #define HAVE_PROC_STAT 1
 #define HAVE_PROC_MAPS 1
 #define HAVE_PROC_SMAPS 1
+#define HAVE_PROC_SOMAXCONN 1
 #endif
 
 /* Test for task_info() */
diff --git a/src/redis.c b/src/redis.c
index 25f9e568..32b54e4f 100644
--- a/src/redis.c
+++ b/src/redis.c
@@ -1621,6 +1621,23 @@ void adjustOpenFilesLimit(void) {
     }
 }
 
+/* Check that server.tcp_backlog can be actually enforced in Linux according
+ * to the value of /proc/sys/net/core/somaxconn, or warn about it. */
+void checkTcpBacklogSettings(void) {
+#ifdef HAVE_PROC_SOMAXCONN
+    FILE *fp = fopen("/proc/sys/net/core/somaxconn","r");
+    char buf[1024];
+    if (!fp) return;
+    if (fgets(buf,sizeof(buf),fp) != NULL) {
+        int somaxconn = atoi(buf);
+        if (somaxconn > 0 && somaxconn < server.tcp_backlog) {
+            redisLog(REDIS_WARNING,"WARNING: The TCP backlog setting of %d cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of %d.", server.tcp_backlog, somaxconn);
+        }
+    }
+    fclose(fp);
+#endif
+}
+
 /* Initialize a set of file descriptors to listen to the specified 'port'
  * binding the addresses specified in the Redis server configuration.
  *
@@ -3648,6 +3665,7 @@ int main(int argc, char **argv) {
     #ifdef __linux__
         linuxMemoryWarnings();
     #endif
+        checkTcpBacklogSettings();
         loadDataFromDisk();
         if (server.cluster_enabled) {
             if (verifyClusterConfigWithData() == REDIS_ERR) {