http: avoid corking on "Content-Length: 0" response

We must use a normal write instead of send(.., MSG_MORE)
when writing responses of "Content-Length: 0" to avoid
the corking effect MSG_MORE provides.  We only want to
cork headers if we will send a non-empty body.

Fixes: c3eeaf664cf0 ("http: clarify intent for persistence")
This needs a proper test.

1 files changed, 6 insertions, 5 deletions

diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index 39345122..c7fb954e 100644
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -151,7 +151,7 @@ sub response_header_write {
         my $proto = $env->{SERVER_PROTOCOL} or return; # HTTP/0.9 :P
         my $status = $res->[0];
         my $h = "$proto $status " . status_message($status) . "\r\n";
-        my $term;
+        my ($len, $chunked);
         my $headers = $res->[1];
 
         for (my $i = 0; $i < @$headers; $i += 2) {
@@ -159,14 +159,15 @@ sub response_header_write {
                 my $v = $headers->[$i + 1];
                 next if $k =~ /\A(?:Connection|Date)\z/i;
 
-                if ($k =~ /\AContent-Length\z/ ||
-                    ($k =~ /\ATransfer-Encoding\z/i && $v =~ /\bchunked\b/i)) {
-                        $term = 1;
+                $len = $v if $k =~ /\AContent-Length\z/i;
+                if ($k =~ /\ATransfer-Encoding\z/i && $v =~ /\bchunked\b/i) {
+                        $chunked = 1;
                 }
                 $h .= "$k: $v\r\n";
         }
 
         my $conn = $env->{HTTP_CONNECTION} || '';
+        my $term = defined($len) || $chunked;
         my $alive = $term &&
                         (($proto eq 'HTTP/1.1' && $conn !~ /\bclose\b/i) ||
                          ($conn =~ /\bkeep-alive\b/i));
@@ -174,7 +175,7 @@ sub response_header_write {
         $h .= 'Connection: ' . ($alive ? 'keep-alive' : 'close');
         $h .= "\r\nDate: " . http_date() . "\r\n\r\n";
 
-        if ($term && $env->{REQUEST_METHOD} ne 'HEAD') {
+        if (($len || $chunked) && $env->{REQUEST_METHOD} ne 'HEAD') {
                 more($self, $h);
         } else {
                 $self->write($h);