Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/docs/libcurl/opts/CURLINFO_OS_ERRNO.md

@@ -0,0 +1,72 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: CURLINFO_OS_ERRNO
+Section: 3
+Source: libcurl
+See-also:
+  - curl_easy_getinfo (3)
+  - curl_easy_setopt (3)
+Protocol:
+  - All
+Added-in: 7.12.2
+---
+
+# NAME
+
+CURLINFO_OS_ERRNO - get errno number from last connect failure
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_OS_ERRNO, long *errnop);
+~~~
+
+# DESCRIPTION
+
+Pass a pointer to a long to receive the errno variable from a connect failure.
+Note that the value is only set on failure, it is not reset upon a successful
+operation. The number is OS and system specific.
+
+libcurl network-related errors that may have a saved errno are:
+CURLE_COULDNT_CONNECT, CURLE_FAILED_INIT, CURLE_INTERFACE_FAILED,
+CURLE_OPERATION_TIMEDOUT, CURLE_RECV_ERROR, CURLE_SEND_ERROR.
+
+Since 8.8.0 libcurl clears the easy handle's saved errno before performing the
+transfer. Prior versions did not clear the saved errno, which means if a saved
+errno is retrieved it could be from a previous transfer on the same handle.
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURL *curl = curl_easy_init();
+  if(curl) {
+    CURLcode res;
+    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
+    res = curl_easy_perform(curl);
+    if(res != CURLE_OK) {
+      long error;
+      res = curl_easy_getinfo(curl, CURLINFO_OS_ERRNO, &error);
+      if(!res && error) {
+        printf("Errno: %ld\n", error);
+      }
+    }
+    curl_easy_cleanup(curl);
+  }
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+curl_easy_getinfo(3) returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).