getaddrinfo and AF_UNSPEC w/ IPv4/6 messes up ai_canonname?

[Pekka Savola]

Hello,

I noticed something strange when using getaddrinfo to get both IPv4 and 
IPv6 addresses w/ AI_CANONNAME.

I wrote (or parsed together) a small, attached test program to demonstrate 
this.

On Linux I get like:

pekkas: /home/pekkas$ ./test-canonname
host: ftp.kame.net, canon (if any): 3ffe:501:4819:2000:210:f3ff:fe03:4d0
pekkas: /home/pekkas$ ./test-canonname
host: ftp.kame.net, canon (if any): 2001:200:0:4819:210:f3ff:fe03:4d0

On e.g. FreeBSD I get like:

$ ./test-canonname
host: ftp.kame.net, canon (if any): kame220.kame.net

2001:200:0:4819:210:f3ff:fe03:4d0 or 3ffe:501:4819:2000:210:f3ff:fe03:4d 
are _not_ canonical names, so it looks like a bug.

Thanks,

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords
-------------- next part --------------
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/param.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>

#include <err.h>
#include <errno.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>

int main(void) {

        int error;
        struct addrinfo hints, *res0;
        static char hostnamebuf[MAXHOSTNAMELEN];
        char *port = "21";
        char *host = "ftp.kame.net";

        memset(&hints, 0, sizeof(hints));
        memset(&res0, 0, sizeof(res0));

        hints.ai_flags = AI_CANONNAME;
        hints.ai_family = PF_UNSPEC;
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_protocol = 0;
        error = getaddrinfo(host, port, &hints, &res0);
        if (error) {
                warnx("%s: %s", host, gai_strerror(error));
                if (error == EAI_SYSTEM)
                        warnx("%s: %s", host, strerror(errno));
                return (0);
        }

        if (res0->ai_canonname)
                (void) strncpy(hostnamebuf, res0->ai_canonname,
                               sizeof(hostnamebuf));

	printf("host: %s, canon (if any): %s\n", host, hostnamebuf);

	return (0);
}