daemon: set TCP_DEFER_ACCEPT on everything but NNTP

This Linux-specific option can save us some wakeups during
the TLS negotiation phase, and it can help with ordinary HTTP,
too.

Plain NNTP (and in the future, POP3) are the only things which
require the server send messages, first.

1 files changed, 19 insertions, 0 deletions

diff --git a/t/httpd-corner.t b/t/httpd-corner.t
index c1dc77db..13befcf1 100644
--- a/t/httpd-corner.t
+++ b/t/httpd-corner.t
@@ -36,6 +36,17 @@ my %opts = (
         Listen => 1024,
 );
 my $sock = IO::Socket::INET->new(%opts);
+my $defer_accept_val;
+if ($^O eq 'linux') {
+        setsockopt($sock, IPPROTO_TCP, Socket::TCP_DEFER_ACCEPT(), 5) or die;
+        my $x = getsockopt($sock, IPPROTO_TCP, Socket::TCP_DEFER_ACCEPT());
+        defined $x or die "getsockopt: $!";
+        $defer_accept_val = unpack('i', $x);
+        if ($defer_accept_val <= 0) {
+                die "unexpected TCP_DEFER_ACCEPT value: $defer_accept_val";
+        }
+}
+
 my $upath = "$tmpdir/s";
 my $unix = IO::Socket::UNIX->new(
         Listen => 1024,
@@ -497,6 +508,14 @@ SKIP: {
         is($body, sha1_hex(''), 'read expected body #2');
 }
 
+SKIP: {
+        skip 'TCP_DEFER_ACCEPT is Linux-only', 1 if $^O ne 'linux';
+        my $var = Socket::TCP_DEFER_ACCEPT();
+        defined(my $x = getsockopt($sock, IPPROTO_TCP, $var)) or die;
+        is(unpack('i', $x), $defer_accept_val,
+                'TCP_DEFER_ACCEPT unchanged if previously set');
+};
+
 done_testing();
 
 sub capture {