splithttp: bind sendThrough=origin to the real per-connection local IP#6476
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echoowall wants to merge 2 commits into
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splithttp: bind sendThrough=origin to the real per-connection local IP#6476echoowall wants to merge 2 commits into
echoowall wants to merge 2 commits into
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The XHTTP inbound set every accepted connection's LocalAddr to the
listener's address (h.localAddr = l.listener.Addr()). On a wildcard
listener that is the unspecified address ("[::]" / "0.0.0.0").
sendThrough "origin" derives the outbound gateway from inbound.Local,
which comes from conn.LocalAddr(). So with XHTTP every connection's
egress was bound to the wildcard, collapsing all entry IPs onto one
(often IPv6) source address and breaking source-in-source-out on
multi-IP hosts (and failing outright when that address has no route).
Read the concrete per-connection local address from the request context
(http.LocalAddrContextKey), which net/http populates with the address
the client actually connected to. Fall back to the listener address when
the key is absent (e.g. HTTP/3, where net/http does not set it).
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Problem
With
sendThrough: "origin"(source-in-source-out), the outbound gateway is derived frominbound.Local, which is set fromconn.LocalAddr()of the accepted connection (app/proxyman/inbound/worker.go).For the XHTTP (splithttp) inbound, every accepted connection's
LocalAddris set toh.localAddr, which is the listener address (l.listener.Addr()). On a wildcard listener that is the unspecified address ([::]or0.0.0.0).Consequences on a multi-IP host:
sendThrough: originreads the wildcard[::]for every connection, so all egress is bound to a single (often IPv6) source address regardless of which local IP the client actually connected to — source-in-source-out silently stops working.[::]has no route, the outbound fails entirely: the REALITY handshake and VLESS tunnel come up, but no data flows (network is unreachable).TCP inbounds are unaffected because
worker.goalready uses the realconn.LocalAddr(); only XHTTP substitutes the listener address.Fix
Read the concrete per-connection local address from the request context via
http.LocalAddrContextKey, whichnet/httppopulates with the address the client actually connected to. Fall back to the listener address when the key is absent (e.g. HTTP/3, wherenet/httpdoes not set it), preserving current behavior there.Verification
Confirmed under HTTP/2 on a wildcard
[::]listener thatrequest.Context().Value(http.LocalAddrContextKey)returns the concrete IP the client connected to (different entry IP → different value), whereasl.listener.Addr()is always[::].End-to-end on a 5-IP host running
sendThrough: origin+ VLESS/REALITY/XHTTP: before the patch all egress bound[::](broken on a host without IPv6 route); after the patch each entry IP egresses via the matching source IP (.38→.38,.49→.49, …), all reachable.