nntp: support COMPRESS DEFLATE per RFC 8054

This is only tested so far with my patches to Net::NNTP at:
https://rt.cpan.org/Ticket/Display.html?id=129967

Memory use in C10K situations is disappointing, but that's
the nature of compression.

gzip compression over HTTPS does have the advantage of not
keeping zlib streams open when clients are idle, at the
cost of worse compression.

1 files changed, 22 insertions, 1 deletions

diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 631fd3c7..d6f315ba 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -20,6 +20,7 @@ use Time::Local qw(timegm timelocal);
 use constant {
         LINE_MAX => 512, # RFC 977 section 2.3
         r501 => '501 command syntax error',
+        r502 => '502 Command unavailable',
         r221 => '221 Header follows',
         r224 => '224 Overview information follows (multi-line)',
         r225 =>        '225 Headers follow (multi-line)',
@@ -41,6 +42,7 @@ LIST ACTIVE ACTIVE.TIMES NEWSGROUPS OVERVIEW.FMT\r
 HDR\r
 OVER\r
 
+my $have_deflate;
 my $EXPMAP; # fd -> [ idle_time, $self ]
 my $expt;
 our $EXPTIME = 180; # 3 minutes
@@ -897,11 +899,13 @@ sub cmd_xover ($;$) {
         });
 }
 
+sub compressed { undef }
+
 sub cmd_starttls ($) {
         my ($self) = @_;
         my $sock = $self->{sock} or return;
         # RFC 4642 2.2.1
-        (ref($sock) eq 'IO::Socket::SSL') and return '502 Command unavailable';
+        return r502 if (ref($sock) eq 'IO::Socket::SSL' || $self->compressed);
         my $opt = $self->{nntpd}->{accept_tls} or
                 return '580 can not initiate TLS negotiation';
         res($self, '382 Continue with TLS negotiation');
@@ -910,6 +914,17 @@ sub cmd_starttls ($) {
         undef;
 }
 
+# RFC 8054
+sub cmd_compress ($$) {
+        my ($self, $alg) = @_;
+        return '503 Only the DEFLATE is supported' if uc($alg) ne 'DEFLATE';
+        return r502 if $self->compressed || !$have_deflate;
+        res($self, '206 Compression active');
+        PublicInbox::NNTPdeflate->enable($self);
+        $self->requeue;
+        undef
+}
+
 sub cmd_xpath ($$) {
         my ($self, $mid) = @_;
         return r501 unless $mid =~ /\A<(.+)>\z/;
@@ -997,4 +1012,10 @@ sub busy {
         ($self->{rbuf} || $self->{wbuf} || not_idle_long($self, $now));
 }
 
+# this is an import to prevent "perl -c" from complaining about fields
+sub import {
+        $have_deflate = eval { require PublicInbox::NNTPdeflate } and
+                $CAPABILITIES .= "COMPRESS DEFLATE\r\n";
+}
+
 1;