osmo_sock_init/getaddrinfo not working for GRE/SOCKET_RAW

[Pablo Neira Ayuso]

On Thu, Nov 22, 2012 at 10:36:34PM +0100, Pablo Neira Ayuso wrote:
> Hi Holger!
> 
> On Wed, Nov 07, 2012 at 03:21:14PM +0100, Holger Hans Peter Freyther wrote:
> > Dear Pablo,
> > 
> > getaddrinfo does not work for the combination of AF_INET, SOCK_RAW
> > and IPPROTO_GRE. I have attached an example application that can be
> > compiled with:
> > 
> >   $ gcc -o fr fr.c `pkg-config --cflags --libs libosmocore libosmogb`
> > 
> > this prints:
> > getaddrinfo returned NULL: Success
> > FAILED
> 
> $ strace ./fr
> [...]
> socket(PF_NETLINK, SOCK_RAW, 0)         = 3
> bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
> getsockname(3, {sa_family=AF_NETLINK, pid=5936, groups=00000000}, [12]) = 0
> sendto(3, "\24\0\0\0\26\0\1\3+\230\256P\0\0\0\0\0\0\0\0", 20, 0, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
> msg_iov(1)=[{"0\0\0\0\24\0\2\0+\230\256P0\27\0\0\2\10\200\376\1\0\0\0\10\0\1\0\177\0\0\1"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 108
> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
> msg_iov(1)=[{"@\0\0\0\24\0\2\0+\230\256P0\27\0\0\n\200\200\376\1\0\0\0\24\0\1\0\0\0\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 128
> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
> msg_iov(1)=[{"\24\0\0\0\3\0\2\0+\230\256P0\27\0\0\0\0\0\0\1\0\0\0\24\0\1\0\0\0\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 20
> 
> The interesting thing is that the function calls rtnetlink to obtain
> address information from the kernel, and it seems it gets it right.
> 
> Let me decipher that netlink trace:
> 
> 1) bind(3, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 0
>                                                         ^^
>    bind this socket to rtnetlink
> 
> 2) Send the request message to ask for the address information.
> 
> sendto(3, "\24\0\0\0\26\0\1\3+\230\256P\0\0\0\0\0\0\0\0", 20, 0, {sa_family=AF_NETLINK, pid=0, groups=00000000}, 12) = 20
> 
> 3) We get the multipart message with the information that we
> requested:
> 
> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
> msg_iov(1)=[{"0\0\0\0\24\0\2\0+\230\256P0\27\0\0\2\10\200\376\1\0\0\0\10\0\1\0\177\0\0\1"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 108
> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
> msg_iov(1)=[{"@\0\0\0\24\0\2\0+\230\256P0\27\0\0\n\200\200\376\1\0\0\0\24\0\1\0\0\0\0\0"..., 4096}], msg_controllen=0, msg_flags=0}, 0) = 128
> recvmsg(3, {msg_name(12)={sa_family=AF_NETLINK, pid=0, groups=00000000},
> 
> The problem seems to be in glibc, at sysdeps/posix/getaddrinfo.c, line 125:
> 
>   { SOCK_RAW, 0, GAI_PROTO_PROTOANY|GAI_PROTO_NOSERVICE, true, "raw" }
> 
> The GAI_PROTO_NOSERVICE flag is set, while interating over the list of
> addresses that it has obtained from the kernel to return the addrinfo
> object, it seems to skip the raw protocol and it returns EAI_SERVICE.

To be more precise, it returns EAI_SERVICE before even iterating over
the list of address.

This behaviour seems a bit inconsistent to me, ie. requst data from
the kernel, get it all right and discard it :-)