Cleanup host UDS support

This change fixes several issues with the fsgofer host UDS support. Notably, it
adds support for SOCK_SEQPACKET and SOCK_DGRAM sockets [1]. It also fixes
unsafe use of unet.Socket, which could cause a panic if Socket.FD is called
when err != nil, and calls to Socket.FD with nothing to prevent the garbage
collector from destroying and closing the socket.

A set of tests is added to exercise host UDS access. This required extracting
most of the syscall test runner into a library that can be used by custom
tests.

Updates #235
Updates #1003

[1] N.B. SOCK_DGRAM sockets are likely not particularly useful, as a server can
only reply to a client that binds first. We don't allow bind, so these are
unlikely to be used.

PiperOrigin-RevId: 275558502

2 files changed, 0 insertions, 11 deletions

diff --git a/pkg/fd/BUILD b/pkg/fd/BUILD
index c7f549428..afa8f7659 100644
--- a/pkg/fd/BUILD
+++ b/pkg/fd/BUILD
@@ -8,9 +8,6 @@ go_library(
     srcs = ["fd.go"],
     importpath = "gvisor.dev/gvisor/pkg/fd",
     visibility = ["//visibility:public"],
-    deps = [
-        "//pkg/unet",
-    ],
 )
 
 go_test(
diff --git a/pkg/fd/fd.go b/pkg/fd/fd.go
index 7691b477b..83bcfe220 100644
--- a/pkg/fd/fd.go
+++ b/pkg/fd/fd.go
@@ -22,8 +22,6 @@ import (
 	"runtime"
 	"sync/atomic"
 	"syscall"
-
-	"gvisor.dev/gvisor/pkg/unet"
 )
 
 // ReadWriter implements io.ReadWriter, io.ReaderAt, and io.WriterAt for fd. It
@@ -187,12 +185,6 @@ func OpenAt(dir *FD, path string, flags int, mode uint32) (*FD, error) {
 	return New(f), nil
 }
 
-// DialUnix connects to a Unix Domain Socket and return the file descriptor.
-func DialUnix(path string) (*FD, error) {
-	socket, err := unet.Connect(path, false)
-	return New(socket.FD()), err
-}
-
 // Close closes the file descriptor contained in the FD.
 //
 // Close is safe to call multiple times, but will return an error after the