Make redisEnableKeepAlive a no-op on AF_UNIX connections.

Fixes #1185

.gitignore

@@ -7,3 +7,4 @@
 /*.pc
 *.dSYM
 tags
+compile_commands.json

net.c

@@ -173,6 +173,10 @@ int redisKeepAlive(redisContext *c, int interval) {
     int val = 1;
     redisFD fd = c->fd;
 
+    /* TCP_KEEPALIVE makes no sense with AF_UNIX connections */
+    if (c->connection_type == REDIS_CONN_UNIX)
+        return REDIS_ERR;
+
 #ifndef _WIN32
     if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof(val)) == -1){
         __redisSetError(c,REDIS_ERR_OTHER,strerror(errno));

test.c

@@ -431,6 +431,24 @@ static void test_tcp_options(struct config cfg) {
     redisFree(c);
 }
 
+static void test_unix_keepalive(struct config cfg) {
+    redisContext *c;
+    redisReply *r;
+
+    c = do_connect(cfg);
+
+    test("Setting TCP_KEEPALIVE on a unix socket returns an error: ");
+    test_cond(redisEnableKeepAlive(c) == REDIS_ERR && c->err == 0);
+
+    test("Setting TCP_KEEPALIVE on a unix socket doesn't break the connection: ");
+    r = redisCommand(c, "PING");
+    test_cond(r != NULL && r->type == REDIS_REPLY_STATUS && r->len == 4 &&
+              !memcmp(r->str, "PONG", 4));
+    freeReplyObject(r);
+
+    redisFree(c);
+}
+
 static void test_reply_reader(void) {
     redisReader *reader;
     void *reply, *root;
@@ -2363,6 +2381,7 @@ int main(int argc, char **argv) {
         test_blocking_connection_timeouts(cfg);
         test_blocking_io_errors(cfg);
         test_invalid_timeout_errors(cfg);
+        test_unix_keepalive(cfg);
         if (throughput) test_throughput(cfg);
     } else {
         test_skipped();