fix: fragment CRYPTO flight to honor peer max_udp_payload_size (#2)#3
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…size (#2) Also advertise only the configured version_preference in the version_information transport param instead of all supported_versions.
javiergarea
approved these changes
Jun 2, 2026
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Closes #2.
The server packed its entire Handshake CRYPTO flight (~1550 bytes) into one
datagram, exceeding the 1472-byte max_udp_payload_size quiche
advertises. Client dropped it with ERR_MSG_TOO_BIG before decryption and timed
out (quic_error 67); curl/ngtcp2 tolerated it, hiding the bug.
flush_handshake/1 now uses build_handshake_packets/2 to split the flight across
packets, fragmenting CRYPTO at its offset boundary (RFC 9000 §19.6) so no
datagram exceeds min(max_payload_size, peer max_udp_payload_size).
Also advertise only the configured version_preference in the version_information transport param instead of all supported_versions.