pipe: add flb_pipe_error

[braydonk]

On Windows, the flb_pipe_r and flb_pipe_w macros do not set errno on failure, meaning calling flb_errno in error scenarios is insufficient. This PR adds a new macro that will check the correct place, WSAGetLastError, and output a similar error message. On Linux this will still be flb_errno, meaning messages should work the same as they always did, but now on Windows we will get actual error messages.

Fixes #3146

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Testing
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• Example configuration file for the change
• Debug log output from testing the change

I had trouble finding a scenario wherein a proper winsock.h failure is propagated. In #3146 they mentioned sending to an elasticsearch host that is not available, but the pattern for how the http client handles that error appears to have changed such that a direct pipe read error isn't propagated.

To test the log format, I made this local change on Windows:

--- a/src/flb_utils.c
+++ b/src/flb_utils.c
@@ -494,7 +494,9 @@ int flb_utils_timer_consume(flb_pipefd_t fd)
     int ret;
     uint64_t val;

-    ret = flb_pipe_r(fd, &val, sizeof(val));
+    // ret = flb_pipe_r(fd, &val, sizeof(val));
+    ret = -1;
+    WSASetLastError(WSAEADDRINUSE);
     if (ret == -1) {
         flb_pipe_error();
         return -1;

Resulting log:

[2025/02/27 18:01:58] [error] [C:\Users\braydonk\Git\fluent-bit\src\flb_utils.c:501 WSAGetLastError=10048] Only one usage of each socket address (protocol/network address/port) is normally permitted.

On Linux I made the following similar local change:

--- a/src/flb_utils.c
+++ b/src/flb_utils.c
@@ -494,7 +494,9 @@ int flb_utils_timer_consume(flb_pipefd_t fd)
     int ret;
     uint64_t val;
 
-    ret = flb_pipe_r(fd, &val, sizeof(val));
+    // ret = flb_pipe_r(fd, &val, sizeof(val));
+    ret = -1;
+    errno = EADDRINUSE;
     if (ret == -1) {
         flb_pipe_error();
         return -1;

And this is the resulting error message:

[2025/02/28 13:57:17] [error] [/usr/local/google/home/braydonk/Git/fluent-bit/src/flb_utils.c:501 errno=98] Address already in use

• Attached Valgrind output that shows no leaks or memory corruption was found

Documentation

Docs PR should not be required.

Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[braydonk]

That s390x failure doesn't look related to this PR.