Date: Thu, 12 Jul 2012 14:21:38 -0700 From: Doug Hardie <bc979@lafn.org> To: Matthias Apitz <guru@unixarea.de> Cc: freebsd-questions@freebsd.org Subject: Re: IPv6 && getaddrinfo(3C) Message-ID: <80BE761E-42B1-4111-ACEC-0C31E43D105D@lafn.org> In-Reply-To: <20120712142415.GA1624@tiny.Sisis.de> References: <20120712142415.GA1624@tiny.Sisis.de>
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On 12 July 2012, at 07:24, Matthias Apitz wrote:
>=20
> Hello,
>=20
> I'm playing around with IPv6 code on a FreeBSD 9 system and can't get
> getaddrinfo(3C) to do what it should do as stated in its man page:
> accept an IPv6 and IPv4 IP addr, it only works with the IPv6 form:
>=20
> $ ./a.out ::1
> host: ::1
> read: SSH-2.0-OpenSSH_5.6p1 FreeBSD-20101111
> $ ./a.out 127.0.0.1
> host: 127.0.0.1
> ssh: getaddrinfo failed code 8: hostname nor servname provided, or not =
known
> $ telnet 127.0.0.1 22
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> SSH-2.0-OpenSSH_5.6p1 FreeBSD-20101111
>=20
> the used C-code is attached below; what I'm doing wrong in the code?
>=20
> Thanks
>=20
> matthias
>=20
> /* IPv6 client code using getaddrinfo */
>=20
> #include <stdlib.h>
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> #include <stdio.h>
> #include <netdb.h>
> #include <string.h>
>=20
>=20
> main(argc, argv) /* client side */
> int argc;
> char *argv[];
> {
>=20
> struct addrinfo req, *ans;
> int code, s, n;
> char buf[1024];
>=20
> memset(&req, 0, sizeof(req));
> req.ai_flags =3D AI_ADDRCONFIG|AI_NUMERICHOST;
> req.ai_family =3D AF_INET6; /* Same as AF_INET6. */
> req.ai_socktype =3D SOCK_STREAM;
>=20
> /* */
> /* Use default protocol (in this case tcp) */
> /* */
>=20
> req.ai_protocol =3D 0;
>=20
> printf("host: %s\n", argv[1]);
> if ((code =3D getaddrinfo(argv[1], "ssh", &req, &ans)) !=3D 0) {
> fprintf(stderr, "ssh: getaddrinfo failed code %d: %s\n", =
code, gai_strerror(code));
> exit(1);
> }
> =20
> =20
> /* */
> /* ans must contain at least one addrinfo, use */
> /* the first. */
> /* */=20
> =09
> s =3D socket(ans->ai_family, ans->ai_socktype, =
ans->ai_protocol);
> if (s < 0) {
> perror("ssh: socket");
> exit(3);
> }
>=20
> /* Connect does the bind for us */
> =09
> if (connect(s, ans->ai_addr, ans->ai_addrlen) < 0) {
> perror("ssh: connect");
> exit(5);
> }
>=20
> n =3D read(s, buf, 1024);
> printf ("read: %s", buf);
> =09
> /* */
> /* Free answers after use */
> /* */=20
> freeaddrinfo(ans);
>=20
> exit(0);
> }
>=20
> =20
I won't claim to be an expert on this, but I have used getaddrinfo =
successfully in servers. The only thing I see that might be an issue is =
the use of zero for ai_protocol. The comment in the man page implies =
that value is for servers and not clients. I suspect you have to set =
the specific protocol you want. You haven't included AI_PASSIVE so I =
suspect its expecting you to use the address to contact a server.
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