1 files changed, 74 insertions, 3 deletions
diff --git a/perl/lib/Nix/CopyClosure.pm b/perl/lib/Nix/CopyClosure.pm
index 41ceabd85847..cba365aa1745 100644
--- a/perl/lib/Nix/CopyClosure.pm
+++ b/perl/lib/Nix/CopyClosure.pm
@@ -4,6 +4,15 @@ use strict;
 use Nix::Config;
 use Nix::Store;
 use List::Util qw(sum);
+use IPC::Open2;
+
+
+sub readInt {
+    my ($from) = @_;
+    my $resp;
+    sysread($from, $resp, 8) == 8 or die "did not receive valid reply from remote host\n";
+    return unpack("L<x4", $resp);
+}
 
 
 sub copyTo {
@@ -20,14 +29,76 @@ sub copyTo {
         # Ignore exit status because this is just an optimisation.
     }
 
+    # Start ‘nix-store --serve’ on the remote host.
+    my ($from, $to);
+    my $pid = open2($from, $to, "ssh $sshHost @{$sshOpts} nix-store --serve --write");
+
+    # Do the handshake.
+    eval {
+        my $SERVE_MAGIC_1 = 0x390c9deb; # FIXME
+        my $clientVersion = 0x200;
+        syswrite($to, pack("L<x4L<x4", $SERVE_MAGIC_1, $clientVersion)) or die;
+        die "did not get valid handshake from remote host\n" if readInt($from) != 0x5452eecb;
+        my $serverVersion = readInt($from);
+        die "unsupported server version\n" if $serverVersion < 0x200 || $serverVersion >= 0x300;
+    };
+    if ($@) {
+        chomp $@;
+        warn "$@; falling back to old closure copying method\n";
+        return oldCopyTo(\@closure, @_);
+    }
+
+    # Send the "query valid paths" command with the "lock" option
+    # enabled. This prevens a race where the remote host
+    # garbage-collect paths that are already there.
+    my $req = pack("L<x4L<x4L<x4", 1, 1, scalar @closure);
+    for my $s (@closure) {
+        my $len = length $s;
+        $req .= pack("L<x4", $len);
+        $req .= $s;
+        $req .= "\000" x (8 - $len % 8) if $len % 8;
+    }
+    syswrite($to, $req) or die;
+
+    # Get back the set of paths that are already valid on the remote host.
+    my %present;
+    my $n = readInt($from);
+    while ($n--) {
+        my $len = readInt($from);
+        my $s;
+        sysread($from, $s, $len) == $len or die;
+        $present{$s} = 1;
+        sysread($from, $s, 8 - $len % 8) if $len % 8; # skip padding
+    }
+
+    my @missing = grep { !$present{$_} } @closure;
+    return if !@missing;
+
+    # Send the "import paths" command.
+    syswrite($to, pack("L<x4", 4)) or die;
+    exportPaths(fileno($to), $sign, @missing);
+    readInt($from) == 1 or die;
+
+    # Shut down the server process.
+    close $to;
+    waitpid $pid, 0;
+}
+
+
+# For backwards compatibility with Nix <= 1.7. Will be removed
+# eventually.
+sub oldCopyTo {
+    my ($closure, $sshHost, $sshOpts, $storePaths, $compressor, $decompressor,
+        $includeOutputs, $dryRun, $sign, $progressViewer, $useSubstitutes) = @_;
+
     # Ask the remote host which paths are invalid.  Because of limits
     # to the command line length, do this in chunks.  Eventually,
     # we'll want to use ‘--from-stdin’, but we can't rely on the
     # target having this option yet.
-    my @missing = ();
+    my @missing;
     my $missingSize = 0;
-    while (scalar(@closure) > 0) {
-        my @ps = splice(@closure, 0, 1500);
+    while (scalar(@$closure) > 0) {
+        my @ps = splice(@$closure, 0, 1500);
         open(READ, "set -f; ssh $sshHost @{$sshOpts} nix-store --check-validity --print-invalid @ps|");
         while (<READ>) {
             chomp;