From f73ebbf68989103ed6ec888a6fbff68c21c379c0 Mon Sep 17 00:00:00 2001
From: Sergey Lyubka <valenok@gmail.com>
Date: Wed, 22 Sep 2021 18:52:42 +0100
Subject: [PATCH] Fix #1354 - report correct errno in mg_open_listener()

---
 mongoose.c | 5 ++++-
 src/sock.c | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/mongoose.c b/mongoose.c
index f9eb8001..e1871067 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -2973,6 +2973,7 @@ static void mg_set_non_blocking_mode(SOCKET fd) {
 
 SOCKET mg_open_listener(const char *url, struct mg_addr *addr) {
   SOCKET fd = INVALID_SOCKET;
+  int s_err = 0;  // Memoized socket error, in case closesocket() overrides it
   memset(addr, 0, sizeof(*addr));
   addr->port = mg_htons(mg_url_port(url));
   if (!mg_aton(mg_url_host(url), addr)) {
@@ -3020,12 +3021,14 @@ SOCKET mg_open_listener(const char *url, struct mg_addr *addr) {
       }
       mg_set_non_blocking_mode(fd);
     } else if (fd != INVALID_SOCKET) {
+      s_err = MG_SOCK_ERRNO;
       closesocket(fd);
       fd = INVALID_SOCKET;
     }
   }
   if (fd == INVALID_SOCKET) {
-    LOG(LL_ERROR, ("Failed to listen on %s, errno %d", url, MG_SOCK_ERRNO));
+    if (s_err = 0) s_err = MG_SOCK_ERRNO;
+    LOG(LL_ERROR, ("Failed to listen on %s, errno %d", url, s_err));
   }
 
   return fd;
diff --git a/src/sock.c b/src/sock.c
index f72bd5b6..4accc934 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -127,6 +127,7 @@ static void mg_set_non_blocking_mode(SOCKET fd) {
 
 SOCKET mg_open_listener(const char *url, struct mg_addr *addr) {
   SOCKET fd = INVALID_SOCKET;
+  int s_err = 0;  // Memoized socket error, in case closesocket() overrides it
   memset(addr, 0, sizeof(*addr));
   addr->port = mg_htons(mg_url_port(url));
   if (!mg_aton(mg_url_host(url), addr)) {
@@ -174,12 +175,14 @@ SOCKET mg_open_listener(const char *url, struct mg_addr *addr) {
       }
       mg_set_non_blocking_mode(fd);
     } else if (fd != INVALID_SOCKET) {
+      s_err = MG_SOCK_ERRNO;
       closesocket(fd);
       fd = INVALID_SOCKET;
     }
   }
   if (fd == INVALID_SOCKET) {
-    LOG(LL_ERROR, ("Failed to listen on %s, errno %d", url, MG_SOCK_ERRNO));
+    if (s_err = 0) s_err = MG_SOCK_ERRNO;
+    LOG(LL_ERROR, ("Failed to listen on %s, errno %d", url, s_err));
   }
 
   return fd;