Removes bindDevice from dialOnce's UDP empty-addr path. For relay/listener
UDP sockets, the ListenUDP laddr binding already pins the source IP correctly.
The additional SO_BINDTODEVICE forced all outbound datagrams through the named
interface, which conflicts with the kernel routing table for unconnected UDP
sockets and causes silent packet drops — breaking SOCKS5 UDP associate when
interface is configured.
Fixesgo-gost/gost#287
The switchNetns function was only defined for linux (dialer_netns.go,
build tag linux && !android) and android (dialer_android.go, stub).
This left darwin, freebsd, openbsd, windows, and other platforms with
an undefined symbol at dialer.go:55.
Add no-op stubs to all remaining platform files so the dialer package
compiles on every GOOS.
When using IP aliases on loopback (e.g. ip addr add 10.1.1.1/32 dev lo)
with policy routing, findInterfaceByIP() resolves the alias IP to the
loopback interface. Binding the socket to lo via SO_BINDTODEVICE prevents
outbound traffic from reaching non-local destinations.
Skip SO_BINDTODEVICE when the resolved interface is loopback — source IP
binding via LocalAddr is sufficient for policy routing to steer traffic
through the correct physical interface.
matcher: fix IPv6 normalization via netip.ParseAddr, port-range overwrite
by switching to []*PortRange map, case-insensitive domain/host matching,
glob.MustCompile→Compile to avoid panic on invalid patterns.
plugin: guard nil *Options in NewGRPCConn and NewHTTPClient; add
HTTPClientTransport helper for idle-connection cleanup.
net/*: add doc comments for all exported symbols (no code changes).
Add 30 tests (matcher_test.go 22, plugin_test.go 8) covering all
matcher types, nil safety, case insensitivity, IPv6 normalization,
port ranges, and plugin option composition.
Fix setMark early-return conditions that were inverted relative to
Linux: on FreeBSD (SO_USER_COOKIE) and OpenBSD (SO_RTABLE), a
non-zero mark was short-circuited instead of applied, disabling
socket marking entirely.
Also fix GetClientIP to trim leading whitespace from X-Forwarded-For
entries (per RFC 7239), and fix Body.Read to subtract len(b) instead
of n from recordSize when a single read exceeds the remaining quota.
Add unit tests for internal/net/ (addr, dialer, http, ip, net, pipe,
transport, resolve, proxyproto, udp).
ginuerzh