Public bug reported:
If the AI_ADDRCONFIG flag is passed to getaddrinfo() with AF_INET or
AF_INET6 address families, addresses in /etc/hosts are not resolved
properly.
The following test case illustrates the problem. Its output depends on the
configured networks, but if only "lo" is configured, the output is:
Requested family: 2 [AF_INET]
Error -2: Name or service not known
Requested family: 10 [AF_INET6]
Error -2: Name or service not known
Requested family: 0 [AF_UNSPEC]
Returned family: 10 [AF_INET6]
...
Returned family: 2 [AF_INET]
...
This is inconsistent and wrong (explicit requests for INET or INET6 should both
succeed, given the contents of /etc/hosts). /etc/hosts includes the lines:
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
I see a failure from this behaviour when mounting an NFS share from
localhost when the network is down. It might be argued that
AI_ADDRCONFIG is meaningless with explicit address families, in which
case this is an NFS bug? But the current behaviour is surprising.
--------------------------------------
cat <<EOF >gai.c
#include <netdb.h>
#include <string.h>
#include <stdio.h>
void query(int family)
{
struct addrinfo *ai;
struct addrinfo hint = {
.ai_family = family,
.ai_flags = AI_ADDRCONFIG,
};
int ret = getaddrinfo("localhost", NULL, &hint, &ai);
printf("Requested family: %d\n", hint.ai_family);
if (ret == 0)
while (ai) {
printf("Returned family: %d\n", ai->ai_family);
ai = ai->ai_next;
}
else
printf("Error %d: %s\n", ret, gai_strerror(ret));
}
int
main()
{
query(AF_INET);
query(AF_INET6);
query(AF_UNSPEC);
}
EOF
gcc -o gai gai.c
./gai
** Affects: glibc (Ubuntu)
Importance: Undecided
Status: New
--
Inconsistent behaviour of getaddrinfo() with AI_ADDRCONFIG
https://bugs.launchpad.net/bugs/583278
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