runtime.GOOS=="android" (not "linux"), so StdNetBind enabled UDP_GRO and read
rxOffload=true, but the GRO receive dispatcher in bind_std.go is gated on
GOOS=="linux" → dead on android. A coalesced GRO super-packet was read as one
datagram, corrupting the WG transport stream → download died on no-detour
WG-endpoint (detour path uses ClientBind, no offload, so it worked).
Gate both the UDP_GRO setsockopt (controlfns_linux.go) and the rxOffload
readback (features_linux.go) behind !android. TX/GSO untouched, so non-android
linux performance is unchanged. Confirmed on device (CPH2411/Android-15:
probe gave rxOffload=true + dispatch=single).
See SPECS/010-B-O-WG_ENDPOINT_GRO_SPLIT_BRAIN.
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