fix(client-api): parse single-IP X-Forwarded-For values#4839
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`XForwardedFor::decode` required a comma in the header value via
`split_once(',').ok_or_else(headers::Error::invalid)?`, so any client
coming through a single-hop proxy — which emits `X-Forwarded-For: <ip>`
with no comma — failed to decode.
Previously this was silent: `Option<TypedHeader<XForwardedFor>>` in
`crates/client-api/src/routes/subscribe.rs` resolved to `None` on
decode error under axum 0.7. axum 0.8 (landed in clockworklabs#2713) changed the
behavior: the same decoder `Err` now surfaces as a 400 Bad Request,
which breaks all WebSocket subscribe requests from single-hop proxy
clients — reproducible with:
```
curl -v -H 'Connection: Upgrade' -H 'Upgrade: websocket' \
-H 'Sec-WebSocket-Version: 13' -H 'Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==' \
-H 'Sec-WebSocket-Protocol: v2.bsatn.spacetimedb' \
-H 'x-forwarded-for: 1.2.3.4' \
"http://127.0.0.1:3000/v1/database/test/subscribe?token=..."
# => HTTP/1.1 400 Bad Request
# => invalid HTTP header (x-forwarded-for)
```
Accept both comma-separated and single-IP forms: take the first
entry (trimmed) regardless of whether a comma is present. This
matches how Nginx, Apache, HAProxy, etc. read the same header.
gefjon
approved these changes
Jun 29, 2026
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Summary
XForwardedFor::decoderequires a comma and fails to decodeX-Forwarded-For: 1.2.3.4.Under axum 0.8 this now surfaces as HTTP 400 on every single-hop-proxy request.
Fix
Accept comma-separated or single-IP values — take the first entry either way.
Reproducer
Any browser going through a proxy that does
.insert("x-forwarded-for", client_ip)(standard single-hop pattern) sees 400 Bad Request on WebSocket subscribe.
Version regression
Bug latent since the axum migration in 2023-06 (commit b4dae74). axum 0.7
silently dropped the decoder error via
Option<TypedHeader<T>>; axum 0.8(#2713) promotes it to a 400 rejection.