target = "https://www.rfc-editor.org/rfc/rfc9000#section-14.2.1"

# 14.2.1.  Handling of ICMP Messages by PMTUD
#
# PMTUD [RFC1191] [RFC8201] relies on reception of ICMP messages (that
# is, IPv6 Packet Too Big (PTB) messages) that indicate when an IP
# packet is dropped because it is larger than the local router MTU.
# DPLPMTUD can also optionally use these messages.  This use of ICMP
# messages is potentially vulnerable to attacks by entities that cannot
# observe packets but might successfully guess the addresses used on
# the path.  These attacks could reduce the PMTU to a bandwidth-
# inefficient value.
# 
# An endpoint MUST ignore an ICMP message that claims the PMTU has
# decreased below QUIC's smallest allowed maximum datagram size.
# 
# The requirements for generating ICMP [RFC1812] [RFC4443] state that
# the quoted packet should contain as much of the original packet as
# possible without exceeding the minimum MTU for the IP version.  The
# size of the quoted packet can actually be smaller, or the information
# unintelligible, as described in Section 1.1 of [DPLPMTUD].
# 
# QUIC endpoints using PMTUD SHOULD validate ICMP messages to protect
# from packet injection as specified in [RFC8201] and Section 5.2 of
# [RFC8085].  This validation SHOULD use the quoted packet supplied in
# the payload of an ICMP message to associate the message with a
# corresponding transport connection (see Section 4.6.1 of [DPLPMTUD]).
# ICMP message validation MUST include matching IP addresses and UDP
# ports [RFC8085] and, when possible, connection IDs to an active QUIC
# session.  The endpoint SHOULD ignore all ICMP messages that fail
# validation.
# 
# An endpoint MUST NOT increase the PMTU based on ICMP messages; see
# Item 6 in Section 3 of [DPLPMTUD].  Any reduction in QUIC's maximum
# datagram size in response to ICMP messages MAY be provisional until
# QUIC's loss detection algorithm determines that the quoted packet has
# actually been lost.

[[spec]]
level = "MUST"
quote = '''
An endpoint MUST ignore an ICMP message that claims the PMTU has
decreased below QUIC's smallest allowed maximum datagram size.
'''

[[spec]]
level = "SHOULD"
quote = '''
QUIC endpoints using PMTUD SHOULD validate ICMP messages to protect
from packet injection as specified in [RFC8201] and Section 5.2 of
[RFC8085].
'''

[[spec]]
level = "SHOULD"
quote = '''
This validation SHOULD use the quoted packet supplied in
the payload of an ICMP message to associate the message with a
corresponding transport connection (see Section 4.6.1 of [DPLPMTUD]).
'''

[[spec]]
level = "MUST"
quote = '''
ICMP message validation MUST include matching IP addresses and UDP
ports [RFC8085] and, when possible, connection IDs to an active QUIC
session.
'''

[[spec]]
level = "SHOULD"
quote = '''
The endpoint SHOULD ignore all ICMP messages that fail
validation.
'''

[[spec]]
level = "MUST"
quote = '''
An endpoint MUST NOT increase the PMTU based on ICMP messages; see
Item 6 in Section 3 of [DPLPMTUD].
'''

[[spec]]
level = "MAY"
quote = '''
Any reduction in QUIC's maximum
datagram size in response to ICMP messages MAY be provisional until
QUIC's loss detection algorithm determines that the quoted packet has
actually been lost.
'''