syscall: implement sendmsg+recvmsg in pure Perl

Socket::MsgHdr is only packaged for Debian and derivatives at
the moment, and Inline::C pulling in gcc/clang is a huge amount
of disk space and bandwidth for some users.

This enables disk space and/or bandwidth-limited users to use lei.

Only Linux guarantees a stable ABI and syscall numbers, but
that's the majority of our userbase.  FreeBSD users will still
have to use Inline::C (or get Socket::MsgHdr packaged).

x86, x32, and x86-64 are all currently supported, more to be added.

diff --git a/devel/syscall-list b/devel/syscall-list
index a6b1bfa7781f0fbd10cc3f2330e37a9f584e6feb..d33a8a78a86e00c4534259125fa2c380323d813c 100755 (executable)
--- a/devel/syscall-list
+++ b/devel/syscall-list
@@ -49,6 +49,8 @@ int main(void)
        D(SYS_inotify_rm_watch);
        D(SYS_prctl);
        D(SYS_fstatfs);
+       D(SYS_sendmsg);
+       D(SYS_recvmsg);
 #ifdef FS_IOC_GETFLAGS
        printf("FS_IOC_GETFLAGS=%#lx\nFS_IOC_SETFLAGS=%#lx\n",
                (unsigned long)FS_IOC_GETFLAGS, (unsigned long)FS_IOC_SETFLAGS);

diff --git a/lib/PublicInbox/Syscall.pm b/lib/PublicInbox/Syscall.pm
index 806c192e4b96656317ae1e286bc93b42dd7b8cdd..e9175ceb9cfac0c3ce504be36962d7c7b9e51941 100644 (file)
--- a/lib/PublicInbox/Syscall.pm
+++ b/lib/PublicInbox/Syscall.pm
@@ -2,6 +2,9 @@
 # specifically the Debian libsys-syscall-perl 0.25-6 version to
 # fix upstream regressions in 0.25.
 #
+# See devel/syscall-list in the public-inbox source tree for maintenance
+# <https://80x24.org/public-inbox.git>
+#
 # This license differs from the rest of public-inbox
 #
 # This module is Copyright (c) 2005 Six Apart, Ltd.
@@ -16,6 +19,7 @@ use strict;
 use v5.10.1;
 use parent qw(Exporter);
 use POSIX qw(ENOENT ENOSYS EINVAL O_NONBLOCK);
+use Socket qw(SOL_SOCKET SCM_RIGHTS);
 use Config;
 
 # $VERSION = '0.25'; # Sys::Syscall version
@@ -42,8 +46,19 @@ use constant {
        EPOLL_CTL_ADD => 1,
        EPOLL_CTL_DEL => 2,
        EPOLL_CTL_MOD => 3,
+       SIZEOF_int => $Config{intsize},
+       SIZEOF_size_t => $Config{sizesize},
+       NUL => "\0",
+};
+
+use constant {
+       TMPL_size_t => SIZEOF_size_t == 8 ? 'Q' : 'L',
+       BYTES_4_hole => SIZEOF_size_t == 8 ? 'L' : '',
+       # cmsg_len, cmsg_level, cmsg_type
+       SIZEOF_cmsghdr => SIZEOF_int * 2 + SIZEOF_size_t,
 };
 
+my @BYTES_4_hole = BYTES_4_hole ? (0) : ();
 our $loaded_syscall = 0;
 
 sub _load_syscall {
@@ -68,6 +83,7 @@ our (
      $SYS_renameat2,
      );
 
+my ($SYS_sendmsg, $SYS_recvmsg);
 my $SYS_fstatfs; # don't need fstatfs64, just statfs.f_type
 my ($FS_IOC_GETFLAGS, $FS_IOC_SETFLAGS);
 my $SFD_CLOEXEC = 02000000; # Perl does not expose O_CLOEXEC
@@ -99,6 +115,8 @@ if ($^O eq "linux") {
         $SYS_signalfd4 = 327;
         $SYS_renameat2 //= 353;
        $SYS_fstatfs = 100;
+       $SYS_sendmsg = 370;
+       $SYS_recvmsg = 372;
        $FS_IOC_GETFLAGS = 0x80046601;
        $FS_IOC_SETFLAGS = 0x40046602;
     } elsif ($machine eq "x86_64") {
@@ -108,6 +126,8 @@ if ($^O eq "linux") {
         $SYS_signalfd4 = 289;
        $SYS_renameat2 //= 316;
        $SYS_fstatfs = 138;
+       $SYS_sendmsg = 46;
+       $SYS_recvmsg = 47;
        $FS_IOC_GETFLAGS = 0x80086601;
        $FS_IOC_SETFLAGS = 0x40086602;
     } elsif ($machine eq 'x32') {
@@ -117,6 +137,8 @@ if ($^O eq "linux") {
         $SYS_signalfd4 = 1073742113;
        $SYS_renameat2 //= 0x40000000 + 316;
        $SYS_fstatfs = 138;
+       $SYS_sendmsg = 0x40000206;
+       $SYS_recvmsg = 0x40000207;
        $FS_IOC_GETFLAGS = 0x80046601;
        $FS_IOC_SETFLAGS = 0x40046602;
     } elsif ($machine eq 'sparc64') {
@@ -378,6 +400,79 @@ sub nodatacow_dir {
        if (open my $fh, '<', $_[0]) { nodatacow_fh($fh) }
 }
 
+sub CMSG_ALIGN ($) { ($_[0] + SIZEOF_size_t - 1) & ~(SIZEOF_size_t - 1) }
+use constant CMSG_ALIGN_SIZEOF_cmsghdr => CMSG_ALIGN(SIZEOF_cmsghdr);
+sub CMSG_SPACE ($) { CMSG_ALIGN($_[0]) + CMSG_ALIGN_SIZEOF_cmsghdr }
+sub CMSG_LEN ($) { CMSG_ALIGN_SIZEOF_cmsghdr + $_[0] }
+
+if (defined($SYS_sendmsg) && defined($SYS_recvmsg)) {
+no warnings 'once';
+*send_cmd4 = sub ($$$$) {
+       my ($sock, $fds, undef, $flags) = @_;
+       my $iov = pack('P'.TMPL_size_t,
+                       $_[2] // NUL, length($_[2] // NUL) || 1);
+       my $cmsghdr = pack(TMPL_size_t . # cmsg_len
+                       'LL' .  # cmsg_level, cmsg_type,
+                       ('i' x scalar(@$fds)),
+                       CMSG_LEN(scalar(@$fds) * SIZEOF_int), # cmsg_len
+                       SOL_SOCKET, SCM_RIGHTS, # cmsg_{level,type}
+                       @$fds); # CMSG_DATA
+       my $mh = pack('PL' . # msg_name, msg_namelen (socklen_t (U32))
+                       BYTES_4_hole . # 4-byte padding on 64-bit
+                       'P'.TMPL_size_t . # msg_iov, msg_iovlen,
+                       'P'.TMPL_size_t . # msg_control, msg_controllen,
+                       'i', # msg_flags
+                       NUL, 0, # msg_name, msg_namelen (unused)
+                       @BYTES_4_hole,
+                       $iov, 1, # msg_iov, msg_iovlen
+                       $cmsghdr, # msg_control
+                       CMSG_SPACE(scalar(@$fds) * SIZEOF_int), # msg_controllen
+                       0); # msg_flags
+       my $sent;
+       my $try = 0;
+       do {
+               $sent = syscall($SYS_sendmsg, fileno($sock), $mh, $flags);
+       } while ($sent < 0 &&
+                       ($!{ENOBUFS} || $!{ENOMEM} || $!{ETOOMANYREFS}) &&
+                       (++$try < 50) &&
+                       warn "sleeping on sendmsg: $! (#$try)\n" &&
+                       select(undef, undef, undef, 0.1) == 0);
+       $sent >= 0 ? $sent : undef;
+};
+
+*recv_cmd4 = sub ($$$) {
+       my ($sock, undef, $len) = @_;
+       vec($_[1], ($len + 1) * 8, 1) = 0;
+       vec(my $cmsghdr = '', 256 * 8 - 1, 1) = 1;
+       my $iov = pack('P'.TMPL_size_t, $_[1], $len);
+       my $mh = pack('PL' . # msg_name, msg_namelen (socklen_t (U32))
+                       BYTES_4_hole . # 4-byte padding on 64-bit
+                       'P'.TMPL_size_t . # msg_iov, msg_iovlen,
+                       'P'.TMPL_size_t . # msg_control, msg_controllen,
+                       'i', # msg_flags
+                       NUL, 0, # msg_name, msg_namelen (unused)
+                       @BYTES_4_hole,
+                       $iov, 1, # msg_iov, msg_iovlen
+                       $cmsghdr, # msg_control
+                       256, # msg_controllen
+                       0); # msg_flags
+       my $r = syscall($SYS_recvmsg, fileno($sock), $mh, 0);
+       return (undef) if $r < 0; # $! set
+       substr($_[1], $r, length($_[1]), '');
+       my @ret;
+       if ($r > 0) {
+               my ($len, $lvl, $type, @fds) = unpack(TMPL_size_t . # cmsg_len
+                                       'LLi*', # cmsg_level, cmsg_type, @fds
+                                       $cmsghdr);
+               if ($lvl == SOL_SOCKET && $type == SCM_RIGHTS) {
+                       $len -= CMSG_ALIGN_SIZEOF_cmsghdr;
+                       @ret = @fds[0..(($len / SIZEOF_int) - 1)];
+               }
+       }
+       @ret;
+};
+}
+
 1;
 
 =head1 WARRANTY

diff --git a/script/lei b/script/lei
index 5cad19d776034176552fa352cb6a4415022683e3..adef9944288d91f396a0be0be50f6412d4779de2 100755 (executable)
--- a/script/lei
+++ b/script/lei
@@ -1,5 +1,5 @@
 #!perl -w
-# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict;
 use v5.10.1;
@@ -9,6 +9,10 @@ my $narg = 5;
 my $sock;
 my $recv_cmd = PublicInbox::CmdIPC4->can('recv_cmd4');
 my $send_cmd = PublicInbox::CmdIPC4->can('send_cmd4') // do {
+       require PublicInbox::Syscall;
+       $recv_cmd = PublicInbox::Syscall->can('recv_cmd4');
+       PublicInbox::Syscall->can('send_cmd4');
+} // do {
        my $inline_dir = $ENV{PERL_INLINE_DIRECTORY} //= (
                        $ENV{XDG_CACHE_HOME} //
                        ( ($ENV{HOME} // '/nonexistent').'/.cache' )

diff --git a/t/cmd_ipc.t b/t/cmd_ipc.t
index dd90fa2a63e401962061cece8f1450295f8beb0c..75697a1539e3e8b2b80bb4d1cfa80d685e7d57d5 100644 (file)
--- a/t/cmd_ipc.t
+++ b/t/cmd_ipc.t
@@ -1,5 +1,5 @@
 #!perl -w
-# Copyright (C) 2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict;
 use v5.10.1;
@@ -142,4 +142,15 @@ SKIP: {
        }
 }
 
+SKIP: {
+       skip 'not Linux', 1 if $^O ne 'linux';
+       require_ok 'PublicInbox::Syscall';
+       $send = PublicInbox::Syscall->can('send_cmd4') or
+               skip 'send_cmd4 not defined for arch';
+       $recv = PublicInbox::Syscall->can('recv_cmd4') or
+               skip 'recv_cmd4 not defined for arch';
+       $do_test->(SOCK_STREAM, 0, 'PP Linux stream');
+       $do_test->($SOCK_SEQPACKET, MSG_EOR, 'PP Linux seqpacket');
+}
+
 done_testing;