spawn: support send_fd+recv_fd w/o IO::FDPass

IO::FDPass may be an extra installation burden I don't want to
impose on users.  We only support Linux and *BSDs, however.

2 files changed, 78 insertions, 6 deletions

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 2bc4a916..6f98c934 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -25,6 +25,7 @@ use Text::Wrap qw(wrap);
 use File::Path qw(mkpath);
 use File::Spec;
 our $quit = \&CORE::exit;
+my $recv_fd;
 my $GLP = Getopt::Long::Parser->new;
 $GLP->configure(qw(gnu_getopt no_ignore_case auto_abbrev));
 my $GLP_PASS = Getopt::Long::Parser->new;
@@ -615,7 +616,7 @@ sub accept_dispatch { # Listener {post_accept} callback
         # `say $sock' triggers "die" in lei(1)
         for my $i (0..2) {
                 if (select(my $rout = $rin, undef, undef, 1)) {
-                        my $fd = IO::FDPass::recv(fileno($sock));
+                        my $fd = $recv_fd->(fileno($sock));
                         if ($fd >= 0) {
                                 my $rdr = ($fd == 0 ? '<&=' : '>&=');
                                 if (open(my $fh, $rdr, $fd)) {
@@ -671,7 +672,8 @@ sub lazy_start {
         my $dev_ino_expect = pack('dd', $st[0], $st[1]); # dev+ino
         pipe(my ($eof_r, $eof_w)) or die "pipe: $!";
         my $oldset = PublicInbox::Sigfd::block_signals();
-        require IO::FDPass;
+        $recv_fd = PublicInbox::Spawn->can('recv_fd') or die
+                "Inline::C not installed/configured or IO::FDPass missing\n";
         require PublicInbox::Listener;
         require PublicInbox::EOFpipe;
         (-p STDOUT) or die "E: stdout must be a pipe\n";
diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index 762a0549..4ca94b9f 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -201,12 +201,72 @@ void nodatacow_dir(const char *dir)
 }
 SET_NODATACOW
 
+my $fdpass = <<'FDPASS';
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/socket.h>
+
+#if defined(CMSG_SPACE) && defined(CMSG_LEN)
+union my_cmsg {
+        struct cmsghdr hdr;
+        char pad[sizeof(struct cmsghdr)+8+sizeof(int)+8];
+};
+
+int send_fd(int sockfd, int fd)
+{
+        struct msghdr msg = { 0 };
+        struct iovec iov;
+        union my_cmsg cmsg = { 0 };
+
+        iov.iov_base = &msg.msg_namelen;
+        iov.iov_len = 1;
+        msg.msg_iov = &iov;
+        msg.msg_iovlen = 1;
+        msg.msg_control = &cmsg.hdr;
+        msg.msg_controllen = CMSG_SPACE(sizeof(int));
+
+        cmsg.hdr.cmsg_level = SOL_SOCKET;
+        cmsg.hdr.cmsg_type = SCM_RIGHTS;
+        cmsg.hdr.cmsg_len = CMSG_LEN(sizeof(int));
+        *(int *)CMSG_DATA(&cmsg.hdr) = fd;
+
+        return sendmsg(sockfd, &msg, 0) >= 0;
+}
+
+int recv_fd(int sockfd)
+{
+        union my_cmsg cmsg = { 0 };
+        struct msghdr msg = { 0 };
+        struct iovec iov;
+        int fd = -1;
+
+        iov.iov_base = &msg.msg_namelen;
+        iov.iov_len = 1;
+        msg.msg_iov = &iov;
+        msg.msg_iovlen = 1;
+        msg.msg_control = &cmsg.hdr;
+        msg.msg_controllen = CMSG_SPACE(sizeof(int));
+
+        if (recvmsg(sockfd, &msg, 0) <= 0)
+                return -1;
+
+        errno = EDOM;
+        if (cmsg.hdr.cmsg_level == SOL_SOCKET &&
+                        cmsg.hdr.cmsg_type == SCM_RIGHTS &&
+                        cmsg.hdr.cmsg_len == CMSG_LEN(sizeof(int)))
+                fd = *(int *)CMSG_DATA(&cmsg.hdr);
+
+        return fd;
+}
+#endif /* defined(CMSG_SPACE) && defined(CMSG_LEN) */
+FDPASS
+
 my $inline_dir = $ENV{PERL_INLINE_DIRECTORY} //= (
                 $ENV{XDG_CACHE_HOME} //
                 ( ($ENV{HOME} // '/nonexistent').'/.cache' )
         ).'/public-inbox/inline-c';
 
-$set_nodatacow = $vfork_spawn = undef unless -d $inline_dir && -w _;
+$set_nodatacow = $vfork_spawn = $fdpass = undef unless -d $inline_dir && -w _;
 if (defined $vfork_spawn) {
         # Inline 0.64 or later has locking in multi-process env,
         # but we support 0.5 on Debian wheezy
@@ -215,13 +275,13 @@ if (defined $vfork_spawn) {
                 my $f = "$inline_dir/.public-inbox.lock";
                 open my $fh, '>', $f or die "failed to open $f: $!\n";
                 flock($fh, LOCK_EX) or die "LOCK_EX failed on $f: $!\n";
-                eval 'use Inline C => $vfork_spawn . $set_nodatacow';
+                eval 'use Inline C => $vfork_spawn . $fdpass . $set_nodatacow';
                 my $err = $@;
                 my $ndc_err;
                 if ($err && $set_nodatacow) { # missing Linux kernel headers
                         $ndc_err = $err;
                         undef $set_nodatacow;
-                        eval 'use Inline C => $vfork_spawn';
+                        eval 'use Inline C => $vfork_spawn . $fdpass';
                 }
                 flock($fh, LOCK_UN) or die "LOCK_UN failed on $f: $!\n";
                 die $err if $err;
@@ -229,7 +289,7 @@ if (defined $vfork_spawn) {
         };
         if ($@) {
                 warn "Inline::C failed for vfork: $@\n";
-                $set_nodatacow = $vfork_spawn = undef;
+                $set_nodatacow = $vfork_spawn = $fdpass = undef;
         }
 }
 
@@ -243,8 +303,18 @@ unless ($set_nodatacow) {
         *nodatacow_fd = \&PublicInbox::NDC_PP::nodatacow_fd;
         *nodatacow_dir = \&PublicInbox::NDC_PP::nodatacow_dir;
 }
+unless (__PACKAGE__->can('recv_fd')) {
+        eval { # try the XS IO::FDPass package
+                require IO::FDPass;
+                no warnings 'once';
+                *recv_fd = \&IO::FDPass::recv;
+                *send_fd = \&IO::FDPass::send;
+        };
+}
+
 undef $set_nodatacow;
 undef $vfork_spawn;
+undef $fdpass;
 
 sub which ($) {
         my ($file) = @_;