Use a windows specific keepalive function. (#1104)

Use a windows specific keepalive function.

While it is possible to toggle `TCP_KEEPALIVE` in windows via
setsockopt, you have to use `WSAIoctl` to set the interval.

Since `WSAIoctl` can actually do all of this in one call (toggle the
option, and set the corresponding interval), just use that in Windows
and avoid the call to `setsockopt` alltogether.

Fixes: #1100

net.c

@@ -168,6 +168,7 @@ int redisKeepAlive(redisContext *c, int interval) {
     int val = 1;
     redisFD fd = c->fd;
 
+#ifndef _WIN32
     if (setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof(val)) == -1){
         __redisSetError(c,REDIS_ERR_OTHER,strerror(errno));
         return REDIS_ERR;
@@ -201,7 +202,15 @@ int redisKeepAlive(redisContext *c, int interval) {
     }
 #endif
 #endif
+#else
+    int res;
 
+    res = win32_redisKeepAlive(fd, interval * 1000);
+    if (res != 0) {
+        __redisSetError(c, REDIS_ERR_OTHER, strerror(res));
+        return REDIS_ERR;
+    }
+#endif
     return REDIS_OK;
 }
 

sockcompat.c

@@ -260,4 +260,21 @@ int win32_poll(struct pollfd *fds, nfds_t nfds, int timeout) {
     _updateErrno(ret != SOCKET_ERROR);
     return ret != SOCKET_ERROR ? ret : -1;
 }
+
+int win32_redisKeepAlive(SOCKET sockfd, int interval_ms) {
+    struct tcp_keepalive cfg;
+    DWORD bytes_in;
+    int res;
+
+    cfg.onoff = 1;
+    cfg.keepaliveinterval = interval_ms;
+    cfg.keepalivetime = interval_ms;
+
+    res = WSAIoctl(sockfd, SIO_KEEPALIVE_VALS, &cfg,
+                   sizeof(struct tcp_keepalive), NULL, 0,
+                   &bytes_in, NULL, NULL);
+
+    return res == 0 ? 0 : _wsaErrorToErrno(res);
+}
+
 #endif /* _WIN32 */

sockcompat.h

@@ -50,6 +50,7 @@
 #include <ws2tcpip.h>
 #include <stddef.h>
 #include <errno.h>
+#include <Mstcpip.h>
 
 #ifdef _MSC_VER
 typedef long long ssize_t;
@@ -71,6 +72,8 @@ ssize_t win32_send(SOCKET sockfd, const void *buf, size_t len, int flags);
 typedef ULONG nfds_t;
 int win32_poll(struct pollfd *fds, nfds_t nfds, int timeout);
 
+int win32_redisKeepAlive(SOCKET sockfd, int interval_ms);
+
 #ifndef REDIS_SOCKCOMPAT_IMPLEMENTATION
 #define getaddrinfo(node, service, hints, res) win32_getaddrinfo(node, service, hints, res)
 #undef gai_strerror

test.c

@@ -405,6 +405,16 @@ static void test_append_formatted_commands(struct config config) {
     disconnect(c, 0);
 }
 
+static void test_tcp_options(struct config cfg) {
+    redisContext *c;
+
+    c = do_connect(cfg);
+    test("We can enable TCP_KEEPALIVE: ");
+    test_cond(redisEnableKeepAlive(c) == REDIS_OK);
+
+    disconnect(c, 0);
+}
+
 static void test_reply_reader(void) {
     redisReader *reader;
     void *reply, *root;
@@ -2261,6 +2271,7 @@ int main(int argc, char **argv) {
     test_blocking_io_errors(cfg);
     test_invalid_timeout_errors(cfg);
     test_append_formatted_commands(cfg);
+    test_tcp_options(cfg);
     if (throughput) test_throughput(cfg);
 
     printf("\nTesting against Unix socket connection (%s): ", cfg.unix_sock.path);