QUIC: ignore duplicate PATH_CHALLENGE frames. According to RFC 9000, an endpoint SHOULD NOT send multiple PATH_CHALLENGE frames in a single packet. The change adds a check to enforce this claim to optimize server behavior. Previously each PATH_CHALLENGE always resulted in a single response datagram being sent to client. The effect of this was however limited by QUIC flood protection. Also, PATH_CHALLENGE is explicitly disabled in Initial and Handshake levels, see RFC 9000, Table 3. However, technically it may be sent by client in 0-RTT over a new path without actual migration, even though the migration itself is prohibited during handshake. This allows client to coalesce multiple 0-RTT packets each carrying a PATH_CHALLENGE and end up with multiple PATH_CHALLENGEs per datagram. This again leads to suboptimal behavior, see above. Since the purpose of sending PATH_CHALLENGE frames in 0-RTT is unclear, these frames are now only allowed in 1-RTT. For 0-RTT they are silently ignored.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


CFLAGS = -q -O2 -tWM -w-8004 -w-8012 $(CPU_OPT)

zlib.lib:
	cd $(ZLIB)

	bcc32 -c $(CFLAGS) adler32.c crc32.c deflate.c \
		trees.c zutil.c compress.c \
		inflate.c inffast.c inftrees.c

	tlib zlib.lib +adler32.obj +crc32.obj +deflate.obj \
		+trees.obj +zutil.obj +compress.obj \
		+inflate.obj +inffast.obj +inftrees.obj