Libc getnameinfo length requirement

Christophe Beauval christophebeauval at
Thu Mar 1 22:44:17 UTC 2018

Hello all

This message after having presented the problem below in the freenode 
#freebsd and EFNet #bsdcode channels and being advised (amongst others) 
to use this mailing list.

When I got strange errors (EAI_FAIL) from getnameinfo-calls in a private 
project, I investigated the freebsd/libc/net/getnameinfo.c source code 
and stumbled upon the requirement (in the switch-statement at line 127) 
that the "socklen_t salen" argument needs to be the exact same number as 
"sizeof(struct sockaddr_in)" for the PF_INET protocol family and 
"sizeof(struct sockaddr_in6)" for the PF_INET6 protocol family. This 
fails when using a "sockaddr_storage" struct as first argument and tied 
to this a "sizeof(struct sockaddr_storage)" as second argument, as can 
be found as example in RFC 4038 on page 21 paragraph 6.2.3. For the 
PF_LOCAL protocol family a larger "salen" than it's used struct is also 
not allowed in that switch.

A less strict requirement either allowing any larger size (like in 
glibc's implementation) or at least the size of "struct 
sockaddr_storage" (as suggested by hrs) would solve this problem.

Kind regards

Christophe Beauval

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