infinite loop in esp6_ctlinput()?

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Dear all:

When receiving a "packet too big" ICMP error message, FreeBSD will call 
the ctlinput() function of the upper protocol. If the preceding packet 
is an ESP  IPv6 packet, then FreeBSD will call esp6_ctlinput(). In 
esp6_ctlinput(), pfctlinput2() will be executed to traverse all possible 
upper protocols, and call their registered ctlinput() function. However, 
that would call esp6_ctlinput() again since ESP is one of the upper 
protocols! Then an infinite loop occurs!!

After comparing both IPSEC and FAST_IPSEC, the operations are exactly 
the same. Is it a bug?

Best regards,

Yi-Wen