[PATCH v2] daemon: support listening on Unix domain sockets

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

Listening on Unix domain sockets can be convenient for running
behind reverse proxies, avoiding port conflicts, limiting access,
or avoiding the overhead (if any) of TCP over loopback.
---
 v2: extra tests for binding (not just inheriting),
 setting a permissive umask, and clobbering stale sockets.

 lib/PublicInbox/Daemon.pm |  60 ++++++++++++++++++--------
 t/httpd-corner.t          |  27 +++++++++++-
 t/httpd-unix.t            | 105 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 172 insertions(+), 20 deletions(-)
 create mode 100644 t/httpd-unix.t

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index c101ecb..9f33c05 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -7,6 +7,7 @@ use strict;
 use warnings;
 use Getopt::Long qw/:config gnu_getopt no_ignore_case auto_abbrev/;
 use IO::Handle;
+use IO::Socket;
 STDOUT->autoflush(1);
 STDERR->autoflush(1);
 require Danga::Socket;
@@ -52,17 +53,35 @@ sub daemon_prepare ($) {
 
 	foreach my $l (@cfg_listen) {
 		next if $listener_names{$l}; # already inherited
-		require IO::Socket::INET6; # works for IPv4, too
-		my %o = (
-			LocalAddr => $l,
-			ReuseAddr => 1,
-			Proto => 'tcp',
-		);
-		if (my $s = IO::Socket::INET6->new(%o)) {
+		my (%o, $sock_pkg);
+		if (index($l, '/') == 0) {
+			$sock_pkg = 'IO::Socket::UNIX';
+			eval "use $sock_pkg";
+			die $@ if $@;
+			%o = (Type => SOCK_STREAM, Peer => $l);
+			if (-S $l) {
+				my $c = $sock_pkg->new(%o);
+				if (!defined($c) && $!{ECONNREFUSED}) {
+					unlink $l or die
+"failed to unlink stale socket=$l: $!\n";
+				} # else: let the bind fail
+			}
+			$o{Local} = delete $o{Peer};
+		} else {
+			$sock_pkg = 'IO::Socket::INET6'; # works for IPv4, too
+			eval "use $sock_pkg";
+			die $@ if $@;
+			%o = (LocalAddr => $l, ReuseAddr => 1, Proto => 'tcp');
+		}
+		$o{Listen} = 1024;
+		my $prev = umask 0000;
+		my $s = eval { $sock_pkg->new(%o) };
+		warn "error binding $l: $!\n" unless $s;
+		umask $prev;
+
+		if ($s) {
 			$listener_names{sockname($s)} = $s;
 			push @listeners, $s;
-		} else {
-			warn "error binding $l: $!\n";
 		}
 	}
 	die "No listeners bound\n" unless @listeners;
@@ -165,15 +184,20 @@ sub sockname ($) {
 sub host_with_port ($) {
 	my ($addr) = @_;
 	my ($port, $host);
-	if (length($addr) >= 28) {
-		require Socket6;
-		($port, $host) = Socket6::unpack_sockaddr_in6($addr);
-		$host = '['.Socket6::inet_ntop(Socket6::AF_INET6(), $host).']';
-	} else {
-		($port, $host) = Socket::sockaddr_in($addr);
-		$host = Socket::inet_ntoa($host);
-	}
-	($host, $port);
+
+	# this eval will die on Unix sockets:
+	eval {
+		if (length($addr) >= 28) {
+			require Socket6;
+			($port, $host) = Socket6::unpack_sockaddr_in6($addr);
+			$host = Socket6::inet_ntop(Socket6::AF_INET6(), $host);
+			$host = "[$host]";
+		} else {
+			($port, $host) = Socket::sockaddr_in($addr);
+			$host = Socket::inet_ntoa($host);
+		}
+	};
+	$@ ? ('127.0.0.1', 0) : ($host, $port);
 }
 
 sub inherit () {
diff --git a/t/httpd-corner.t b/t/httpd-corner.t
index 198a7e9..1956407 100644
--- a/t/httpd-corner.t
+++ b/t/httpd-corner.t
@@ -16,6 +16,7 @@ use Digest::SHA qw(sha1_hex);
 use File::Temp qw/tempdir/;
 use Cwd qw/getcwd/;
 use IO::Socket;
+use IO::Socket::UNIX;
 use Fcntl qw(FD_CLOEXEC F_SETFD F_GETFD :seek);
 use Socket qw(SO_KEEPALIVE IPPROTO_TCP TCP_NODELAY);
 use POSIX qw(dup2 mkfifo :sys_wait_h);
@@ -34,20 +35,32 @@ my %opts = (
 	Listen => 1024,
 );
 my $sock = IO::Socket::INET->new(%opts);
+my $upath = "$tmpdir/s";
+my $unix = IO::Socket::UNIX->new(
+	Listen => 1024,
+	Type => SOCK_STREAM,
+	Local => $upath
+);
+ok($unix, 'UNIX socket created');
 my $pid;
 END { kill 'TERM', $pid if defined $pid };
 my $spawn_httpd = sub {
 	my (@args) = @_;
+	$! = 0;
 	my $fl = fcntl($sock, F_GETFD, 0);
 	ok(! $!, 'no error from fcntl(F_GETFD)');
 	is($fl, FD_CLOEXEC, 'cloexec set by default (Perl behavior)');
 	$pid = fork;
 	if ($pid == 0) {
 		# pretend to be systemd
-		fcntl($sock, F_SETFD, $fl &= ~FD_CLOEXEC);
 		dup2(fileno($sock), 3) or die "dup2 failed: $!\n";
+		dup2(fileno($unix), 4) or die "dup2 failed: $!\n";
+		$sock = IO::Handle->new_from_fd(3, 'r');
+		$sock->fcntl(F_SETFD, 0);
+		$unix = IO::Handle->new_from_fd(4, 'r');
+		$unix->fcntl(F_SETFD, 0);
 		$ENV{LISTEN_PID} = $$;
-		$ENV{LISTEN_FDS} = 1;
+		$ENV{LISTEN_FDS} = 2;
 		exec $httpd, @args, "--stdout=$out", "--stderr=$err", $psgi;
 		die "FAIL: $!\n";
 	}
@@ -63,6 +76,16 @@ my $spawn_httpd = sub {
 	$spawn_httpd->('-W0');
 }
 
+# Unix domain sockets
+{
+	my $u = IO::Socket::UNIX->new(Type => SOCK_STREAM, Peer => $upath);
+	ok($u, 'unix socket connected');
+	$u->write("GET /host-port HTTP/1.0\r\n\r\n");
+	$u->read(my $buf, 4096);
+	like($buf, qr!\r\n\r\n127\.0\.0\.1:0\z!,
+		'set REMOTE_ADDR and REMOTE_PORT for Unix socket');
+}
+
 sub conn_for {
 	my ($sock, $msg) = @_;
 	my $conn = IO::Socket::INET->new(
diff --git a/t/httpd-unix.t b/t/httpd-unix.t
new file mode 100644
index 0000000..580d14d
--- /dev/null
+++ b/t/httpd-unix.t
@@ -0,0 +1,105 @@
+# Copyright (C) 2016 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+# Tests for binding Unix domain sockets
+use strict;
+use warnings;
+use Test::More;
+
+foreach my $mod (qw(Plack::Util Plack::Request Plack::Builder Danga::Socket
+			HTTP::Parser::XS HTTP::Date HTTP::Status)) {
+	eval "require $mod";
+	plan skip_all => "$mod missing for httpd-unix.t" if $@;
+}
+
+use File::Temp qw/tempdir/;
+use IO::Socket::UNIX;
+use Cwd qw/getcwd/;
+use Fcntl qw(FD_CLOEXEC F_SETFD F_GETFD :seek);
+my $tmpdir = tempdir('httpd-unix-XXXXXX', TMPDIR => 1, CLEANUP => 1);
+my $unix = "$tmpdir/unix.sock";
+my $httpd = 'blib/script/public-inbox-httpd';
+my $psgi = getcwd() . '/t/httpd-corner.psgi';
+my $out = "$tmpdir/out.log";
+my $err = "$tmpdir/err.log";
+
+my $pid;
+END { kill 'TERM', $pid if defined $pid };
+
+my $spawn_httpd = sub {
+	my (@args) = @_;
+	$pid = fork;
+	if ($pid == 0) {
+		exec $httpd, @args, "--stdout=$out", "--stderr=$err", $psgi;
+		die "FAIL: $!\n";
+	}
+	ok(defined $pid, 'forked httpd process successfully');
+};
+
+ok(!-S $unix, 'UNIX socket does not exist, yet');
+$spawn_httpd->("-l$unix");
+for (1..1000) {
+	last if -S $unix;
+	select undef, undef, undef, 0.02
+}
+
+ok(-S $unix, 'UNIX socket was bound by -httpd');
+sub check_sock ($) {
+	my ($unix) = @_;
+	my $sock = IO::Socket::UNIX->new(Peer => $unix, Type => SOCK_STREAM);
+	ok($sock, 'client UNIX socket connected');
+	ok($sock->write("GET /host-port HTTP/1.0\r\n\r\n"),
+		'wrote req to server');
+	ok($sock->read(my $buf, 4096), 'read response');
+	like($buf, qr!\r\n\r\n127\.0\.0\.1:0\z!,
+		'set REMOTE_ADDR and REMOTE_PORT for Unix socket');
+}
+
+check_sock($unix);
+
+{ # do not clobber existing socket
+	my $fpid = fork;
+	if ($fpid == 0) {
+		open STDOUT, '>>', "$tmpdir/1" or die "redirect failed: $!";
+		open STDERR, '>>', "$tmpdir/2" or die "redirect failed: $!";
+		exec $httpd, '-l', $unix, '-W0', $psgi;
+		die "FAIL: $!\n";
+	}
+	is($fpid, waitpid($fpid, 0), 'second httpd exits');
+	isnt($?, 0, 'httpd failed with failure to bind');
+	open my $fh, "$tmpdir/2" or die "failed to open $tmpdir/2: $!";
+	local $/;
+	my $e = <$fh>;
+	like($e, qr/no listeners bound/i, 'got error message');
+	is(-s "$tmpdir/1", 0, 'stdout was empty');
+}
+
+{
+	my $kpid = $pid;
+	$pid = undef;
+	is(kill('TERM', $kpid), 1, 'terminate existing process');
+	is(waitpid($kpid, 0), $kpid, 'existing httpd terminated');
+	is($?, 0, 'existing httpd exited successfully');
+	ok(-S $unix, 'unix socket still exists');
+}
+{
+	# wait for daemonization
+	$spawn_httpd->("-l$unix", '-D', '-P', "$tmpdir/pid");
+	my $kpid = $pid;
+	$pid = undef;
+	is(waitpid($kpid, 0), $kpid, 'existing httpd terminated');
+	check_sock($unix);
+
+	ok(-f "$tmpdir/pid", 'pid file written');
+	open my $fh, '<', "$tmpdir/pid" or die "open failed: $!";
+	my $rpid = <$fh>;
+	chomp $rpid;
+	like($rpid, qr/\A\d+\z/s, 'pid file looks like a pid');
+	is(kill('TERM', $rpid), 1, 'signalled daemonized process');
+	for (1..100) {
+		kill(0, $rpid) or last;
+		select undef, undef, undef, 0.02;
+	}
+	is(kill(0, $rpid), 0, 'daemonized process exited')
+}
+
+done_testing();
-- 
EW