When no custom resolver or host mapper is configured, xnet.Resolve now
resolves hostnames via Go's native pure-Go resolver (PreferGo: true)
instead of returning the hostname unchanged.
Previously, the unresolved hostname would reach net.Dialer.DialContext,
which on CGO_ENABLED=1 builds used cgo-based DNS — blocking a dedicated
OS thread per concurrent lookup. At scale (1000+ listeners), this
exhausted Go's 10000-thread limit.
Fixesgo-gost/gost#550
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