[PATCH] nntp: delimit Newsgroup: header with commas

[Eric Wong <e@80x24.org>]

Andrey Melnikov <temnota.am@gmail.com> wrote:
> Hi.
> 
> nntpd generate wrong "Newsgoups:" header when message cross-posted to
> multiple groups. Currently, it write multiple groups separated with
> space, but rfc1036 chapter 2.1.3 says "... Multiple newsgroups may be
> specified, separated by a comma. ...".
> and Path: header too - rfc1036 chapter 2.1.6 says " ... The names may
> be separated by any punctuation character or characters (except "."
> which is considered part of the hostname). ..."
> Currently both headers separated as email-style with spaces,

Thanks for the bug report.  Does this break known clients or
is it just something you happened to notice?

I'm using RFC 5536 since it obsoletes 1036.
Testing the following on news.public-inbox.org:

----------8<-------
Subject: [PATCH] nntp: delimit Newsgroup: header with commas

...instead of spaces.  This is specified in RFC 5536 3.1.4.

Include references to RFC 1036, 5536 and 5537 in our docs while
we're at it.

Reported-by: Andrey Melnikov <temnota.am@gmail.com>
Link: https://public-inbox.org/meta/CA+PODjpUN5Q4gBFQhAzUNuMasVEdmp9f=8Uo0Ej0mFumdSwi4w@mail.gmail.com/
---
 Documentation/standards.perl |  3 +++
 lib/PublicInbox/NNTP.pm      | 11 ++++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/Documentation/standards.perl b/Documentation/standards.perl
index 0ac6cc52..1c56830e 100755
--- a/Documentation/standards.perl
+++ b/Documentation/standards.perl
@@ -25,6 +25,9 @@ EOF
 my $rfcs = [
 	3977 => 'NNTP',
 	977 => 'NNTP (old)',
+	1036 => 'Standard for Interchange of USENET Messages',
+	5536 => 'Netnews Article Format',
+	5537 => 'Netnews Architecture and Protocols',
 	6048 => 'NNTP additions to LIST command (TODO)',
 	8054 => 'NNTP compression',
 	4642 => 'NNTP TLS',
diff --git a/lib/PublicInbox/NNTP.pm b/lib/PublicInbox/NNTP.pm
index 102ef42c..783c0076 100644
--- a/lib/PublicInbox/NNTP.pm
+++ b/lib/PublicInbox/NNTP.pm
@@ -432,12 +432,17 @@ sub set_nntp_headers ($$) {
 		$hdr->header_set('X-Alt-Message-ID', @alt);
 	}
 
-	# clobber some
+	# clobber some existing headers
 	my $ibx = $smsg->{-ibx};
 	my $xref = xref($smsg->{nntp}, $ibx, $smsg->{num}, $mid);
 	$hdr->header_set('Xref', $xref);
-	$xref =~ s/:[0-9]+//g;
-	$hdr->header_set('Newsgroups', (split(/ /, $xref, 2))[1]);
+
+	# RFC 5536 3.1.4
+	my $newsgroups = (split(/ /, $xref, 2))[1]; # drop server name
+	$newsgroups =~ s/:[0-9]+\b//g; # drop NNTP article numbers
+	$newsgroups =~ tr/ /,/;
+	$hdr->header_set('Newsgroups', $newsgroups);
+
 	header_append($hdr, 'List-Post', "<mailto:$ibx->{-primary_address}>");
 	if (my $url = $ibx->base_url) {
 		$mid = mid_escape($mid);