Examples?

[ktm5j]

Hello! Could you please provide a working example using both sendSnapshot() and receive() from the libzfs_core module with a simple TCP socket?

I've been trying to make this work and I don't know what I'm doing wrong. I can make it work using plain C with libzfs_core.. any advice would be appreciated!

[adamdruppe]

what code do you have right now?

[ktm5j]

I'm having trouble getting these functions to work in some circumstances.. However just last night I discovered that if use the extern(c) functions from your module directly (lzc_send and lzc_receive) then I can make it work.

For this example, I want to take in 2-3 args from command line: Port to open socket on, snapshot to send and optionally a "from" snapshot. So the command looks like ./send 2020 pool/dataset@snapshot or ./send 2020 pool/dataset@snapshot2 pool/dataset@snapshot1 for an incremental transfer

The following does what I want, using the lzc functions

import core.thread;

import std.conv;
import std.stdio;
import std.socket;
import std.string;

import symmetry.api.libzfs_core;

void main(string[] args) {
    if (args.length < 3)
        exit(1);

    Socket server = new TcpSocket();
    Socket client;
    server.setOption(SocketOptionLevel.SOCKET, SocketOption.REUSEADDR, true);
    server.bind(new InternetAddress(InternetAddress.ADDR_ANY, to!ushort(args[1])));
    server.listen(10);

    assert(datasetExists(args[2]));
    while(true) {
        writeln("Waiting for client");

        try {
            client = server.accept();

            if (args.length >= 4)        // Incremental
                lzc_send(args[2].toCString, args[3].toCString, cast(int)client.handle, cast(lzc_send_flags)0);
            else                         // Single
               lzc_send(args[2].toCString, null, cast(int)client.handle, cast(lzc_send_flags)0);

        } catch (Exception e) {
            logError("error: %s", e.msg);
            logError("sockerr: %s", server.getErrorText());
        }
        client.close();
    }
}

But if I use the sendSnapshot(args[2], client); function with similar inputs then I get a zfs error: 5, strace shows an error occurring during an ioctl call:

socket(AF_INET, SOCK_STREAM, IPPROTO_IP) = 4
bind(4, {sa_family=AF_INET, sin_port=htons(2026), sin_addr=inet_addr("127.0.0.1")}, 16) = 0
listen(4, 10)                           = 0
write(1, "Waiting for client
) = 53
accept(4, NULL, NULL)                   = 5
ioctl(3, _IOC(_IOC_NONE, 0x5a, 0x40, 0), 0x7fffa9208a60) = -1 EINVAL (Invalid argument)
futex(0x7f27d924f1c0, FUTEX_WAKE_PRIVATE, 2147483647) = 0
write(2, "\33[49;38;5;9m", 12)          = 12
write(2, "error: ", 7error: )                  = 7
write(2, "zfs error", 9zfs error)                = 9
write(2, "\33[0m", 4)                   = 4
write(2, "\n", 1
)                       = 1

Any thoughts? Thanks!

[adamdruppe]

Huh, the implementation of that function is similar to what you had:

https://github.com/symmetryinvestments/libzfs-core-d/blob/master/source/symmetry/api/libzfs_core.d#L4937

My guess is that fromSnapshot being "" just might be a problem. Perhaps that is being interpreted differently than null. I don't have a system ready right now to test the code myself, but would you mind copy/pasting this code for me:

ORIGINAL FUNCTION

void sendSnapshot(string snapshotName, Socket socket, SendFlag[] flags=[], string fromSnapshot="")
{
 import std.algorithm:fold;
 auto lzcFlags = flags.fold!((a,b) => a| b)(cast(SendFlag)0).to!lzc_send_flags;
 auto result = lzc_send(snapshotName.toCString, fromSnapshot.toCString,cast(int)socket.handle,lzcFlags);
 enforce(result == 0, "zfs error");
}

NEW FUNCTION

void sendSnapshot(string snapshotName, Socket socket, SendFlag[] flags=[], string fromSnapshot = null) // changed "" to null
{
 import std.algorithm:fold;
 auto lzcFlags = flags.fold!((a,b) => a| b)(cast(SendFlag)0).to!lzc_send_flags;
 auto result = lzc_send(snapshotName.toCString, fromSnapshot.length ? fromSnapshot.toCString : null,cast(int)socket.handle,lzcFlags); // changed fromSnapshot to check for null
 enforce(result == 0, "zfs error");
}

and lemme know? This looks like the only real difference between teh function in there and the function you have working.

[ktm5j]

Yes I based my code off of the implementation of your sendSnapshot() function, which is why it looks so similar! And that's why I was so confused that one would work but not the other.

I should be able to try your alternate code tomorrow, or the weekend at the latest