[PATCH] SSL: optimized SSL_sendfile() usage on FreeBSD

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1769472200 -10800
#      Tue Jan 27 03:03:20 2026 +0300
# Node ID c3f9073f36cc89ee57cc1e09d2de1449060e3687
# Parent  80f7b4a9363e71819963ecc3283c4f41caf12cfc
SSL: optimized SSL_sendfile() usage on FreeBSD.

On FreeBSD sendfile() syscall returns an error with errno set to EAGAIN
when the socket buffer is full (along with the number of bytes sent).
Unfortunately, the SSL_sendfile() interface loses this information, and
an extra SSL_sendfile() call is needed to obtain EAGAIN, typically
resulting in doubled sendfile() syscalls.

With this change, if errno is set to EAGAIN after the SSL_sendfile()
call, we assume it was set by sendfile() and the socket buffer is full.
This is generally safe as we clear errno before the SSL_sendfile() call,
and saves an extra sendfile() syscall.

Prodded by Gleb Smirnoff.

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -3277,6 +3277,10 @@ ngx_ssl_send_chain(ngx_connection_t *c, 
                 send += n;
                 flush = 0;
 
+                if (!c->write->ready) {
+                    break;
+                }
+
                 continue;
             }
 
@@ -3595,7 +3599,7 @@ ngx_ssl_sendfile(ngx_connection_t *c, ng
 
     err = ngx_socket_errno;
 
-    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0, "SSL_sendfile: %z", n);
+    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, err, "SSL_sendfile: %z", n);
 
     if (n > 0) {
 
@@ -3618,6 +3622,16 @@ ngx_ssl_sendfile(ngx_connection_t *c, ng
 
         c->sent += n;
 
+        /*
+         * on FreeBSD sendfile(), along with the number of bytes sent,
+         * returns an error with errno set to EAGAIN when the socket buffer
+         * is full
+         */
+
+        if (err == EAGAIN) {
+            c->write->ready = 0;
+        }
+
         return n;
     }