mirror of
https://github.com/slackhq/nebula.git
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Ryan HuberandClaude Opus 5.5
21075ba32e
internal/msgx is the one copy of xnu's private batched socket calls: the msghdr_x layout, Send/Recv through the raw syscall (EINTR retried) and Unsupported for the errnos a kernel or sandbox refuses them with. Every socket the listener owns reads with recvmsg_x: the listener and each connected socket run their own reader goroutine, and hand whole batches to ListenOut over a channel. ListenOut runs the EncReader over a batch and flushes once, so the reader stays single-threaded without a lock that readers contend on, and the next recvmsg_x overlaps the decrypt of the last batch. Batch buffers (64 x MTU) come from a per-listener free list that keeps up to 11; a reader takes one only while its socket is readable, so idle connected sockets hold none. A batch with a header intact msghdr_x entries can't produce, or ENOSYS/EPERM/EOPNOTSUPP, switches every reader to one datagram per read for good. Connected sockets send runs with sendmsg_x, which xnu batches through the stack on a connected socket. EAGAIN/ENOBUFS keep #1901's single-datagram stall handling; a refused sendmsg_x retries the datagram with write and turns sendmsg_x off once that goes through. The connected-socket knobs lose their NEBULA_CONNSOCK* environment overrides and keep #1901's defaults. Based on Caleb Jasik's #1895 (recvmsg_x) and #1897 (sendmsg_x), and Jack Doan's internal/msgx shape from #1898. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
80 lines
2.3 KiB
Go
80 lines
2.3 KiB
Go
package msgx
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import (
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"bytes"
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"syscall"
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"testing"
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"unsafe"
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"github.com/stretchr/testify/assert"
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"github.com/stretchr/testify/require"
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"golang.org/x/sys/unix"
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)
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// TestHdrLayout pins Hdr to struct msghdr_x's LP64 layout: 56 bytes, Datalen last at 48.
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func TestHdrLayout(t *testing.T) {
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var h Hdr
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assert.EqualValues(t, 56, unsafe.Sizeof(h))
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assert.EqualValues(t, 48, unsafe.Offsetof(h.Datalen))
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}
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// TestSendRecvRoundTrip sends a batch through sendmsg_x in one call and reads it back through recvmsg_x in one
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// call, each message whole, in order, with Datalen set.
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func TestSendRecvRoundTrip(t *testing.T) {
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fds, err := unix.Socketpair(unix.AF_UNIX, unix.SOCK_DGRAM, 0)
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require.NoError(t, err)
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t.Cleanup(func() {
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_ = unix.Close(fds[0])
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_ = unix.Close(fds[1])
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})
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// A dropped datagram fails the receive instead of hanging it.
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require.NoError(t, unix.SetsockoptTimeval(fds[1], unix.SOL_SOCKET, unix.SO_RCVTIMEO, &unix.Timeval{Sec: 2}))
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const n = 5
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var want [n][]byte
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var iovs [n]unix.Iovec
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hdrs := make([]Hdr, n)
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for i := range n {
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want[i] = bytes.Repeat([]byte{byte(i + 1)}, 10+i)
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iovs[i] = unix.Iovec{Base: &want[i][0]}
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iovs[i].SetLen(len(want[i]))
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hdrs[i] = Hdr{Iov: &iovs[i], Iovlen: 1}
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}
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sent, errno := Send(uintptr(fds[0]), hdrs)
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require.Zero(t, errno)
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require.Equal(t, n, sent)
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var bufs [n + 1][64]byte
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var riovs [n + 1]unix.Iovec
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rhdrs := make([]Hdr, n+1)
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for i := range rhdrs {
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riovs[i] = unix.Iovec{Base: &bufs[i][0]}
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riovs[i].SetLen(len(bufs[i]))
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rhdrs[i] = Hdr{Iov: &riovs[i], Iovlen: 1}
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}
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got, errno := Recv(uintptr(fds[1]), rhdrs)
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require.Zero(t, errno)
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require.Equal(t, n, got)
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for i := range n {
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l := int(rhdrs[i].Datalen)
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assert.Equal(t, want[i], bufs[i][:l], "message %d", i)
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}
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}
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// TestEmptyBatch pins that an empty batch is refused before it reaches the kernel.
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func TestEmptyBatch(t *testing.T) {
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_, errno := Send(0, nil)
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assert.Equal(t, syscall.EINVAL, errno)
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_, errno = Recv(0, nil)
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assert.Equal(t, syscall.EINVAL, errno)
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}
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func TestUnsupported(t *testing.T) {
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for _, e := range []syscall.Errno{syscall.ENOSYS, syscall.EPERM, syscall.EOPNOTSUPP} {
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assert.True(t, Unsupported(e), "%v", e)
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}
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for _, e := range []syscall.Errno{0, syscall.EAGAIN, syscall.ENOBUFS, syscall.EINVAL} {
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assert.False(t, Unsupported(e), "%v", e)
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}
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}
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