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authorEric Wong <e@80x24.org>2022-03-23 08:54:35 +0000
committerEric Wong <e@80x24.org>2022-03-23 18:39:03 +0000
commitacefd91b302dc1bffded901c3ecd0db8f9916e9b (patch)
treedc67a37a04c85d503185f12d6c21cb19f01078a3 /lib/PublicInbox
parent215e2138c99d48e2061eb98aef5a6da1bc3ff828 (diff)
downloadpublic-inbox-acefd91b302dc1bffded901c3ecd0db8f9916e9b.tar.gz
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.
Diffstat (limited to 'lib/PublicInbox')
-rw-r--r--lib/PublicInbox/Syscall.pm95
1 files changed, 95 insertions, 0 deletions
diff --git a/lib/PublicInbox/Syscall.pm b/lib/PublicInbox/Syscall.pm
index 806c192e..e9175ceb 100644
--- 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