After the first iteration of the loop, we call memmem with a buflen that
points past the end of buf.
In practice we probably never read the uninitialized memory since we
guarantee the buffer ends with "\r\n", and since most/all libc
implementations probably read the haystack sequentially. But maybe
there's some libc with a crazy optimization out there. It's good to use
an accurate buflen just in case.
Discovered this while running some unit tests with MSan.
Example request that is dying:
NEW REQUEST! lightning_websocketd:main [1955685] <-- bad request from safari
read 507
write_all 1
-> websocket_to_lightningd
-> read_payload_header
read 2
read_all 1
read -11 <--- This tried to read a part of the header, is this -EAGAIN?
read_all 0 should we be blocking on these reads?
*dies*
Fixes#5089
Changelog-Fixed: `experimental-websocket` intermittent read errors fixed
Signed-off-by: William Casarin <jb55@jb55.com>
WebSocket is a bit weird:
1. It starts like an HTTP connection, but they send special headers.
2. We reply with special headers, one of which involves SHA1 of one of theirs.
3. We are then in WebSocket mode, where each frame starts with a 2-20 byte
header.
We relay data in a simplistic way: if either side sends something, we
read it and relay it synchronously. That avoids any gratuitous
buffering.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Matt Morehouse
William Casarin
Rusty Russell