cgo_bridge: export CGoSetEnv so hosts can reach xray-core env knobs - #149
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plutoisnotaplanet wants to merge 1 commit into
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cgo_bridge: export CGoSetEnv so hosts can reach xray-core env knobs#149plutoisnotaplanet wants to merge 1 commit into
plutoisnotaplanet wants to merge 1 commit into
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The Go runtime snapshots environ when the c-archive image initializes, so a
setenv() performed later by a non-Go host is never visible to os.LookupEnv,
which common/platform.EnvFlag relies on.
That makes platform.TunFdKey ("xray.tun.fd") unreachable on iOS: the tun
descriptor only exists after NEPacketTunnelProvider.startTunnel, long after
the snapshot, so the "iOS: use provided fd from NetworkExtension" branch in
proxy/tun/tun_darwin.go can never be taken. NewTun falls through to creating
its own utun via an AF_SYSTEM socket, which the app sandbox denies, and the
inbound fails with "failed to start proxy > operation not permitted".
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Problem
The Go runtime snapshots
environwhen a c-archive image initializes. Asetenv()performed later by the host application is therefore never visibleto
os.LookupEnv, which is whatcommon/platform.EnvFlaguses.That makes every env-based knob in xray-core unreachable from a non-Go host.
The one that matters in practice is
platform.TunFdKey(xray.tun.fd), readby
proxy/tun/tun_darwin.goin the branch commented "iOS: use provided fd fromNetworkExtension".
On iOS the tun descriptor only exists after
NEPacketTunnelProvider.startTunnelruns — long after the snapshot — so aSwift host cannot publish it.
NewTunthen falls through to the macOS path andtries to create its own utun via an
AF_SYSTEMsocket, which the app sandboxdenies:
Reproduced on iPhone 16 Pro / iOS 26.6 with libXray v26.7.28, and isolated with
a minimal spike: a C program calls
setenv("xray.tun.fd", "5", 1)and then anexported Go function —
getenvreturns5,os.LookupEnvreturnsfound=false.Change
One exported function in
cgo_bridge, callingos.Setenvinside the Goruntime. No behavior change for existing callers; nothing else is touched.
With it, the iOS branch of
NewTunfinally becomes reachable: our client nowbrings the tunnel up on device with the same core version that previously
failed at the inbound. The packet path needed no further work — the 4-byte utun
header is handled in
DarwinTun.ReadPacket/WritePacket, which are shared withthe macOS path.
Alternative considered
Passing the descriptor through
TunConfig(afdfield) would be moreexplicit and would not rely on process env at all. That is a larger change to
xray-core's config surface; happy to prepare it instead if maintainers prefer.