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Pablo Neira Ayuso pablo at gnumonks.orgHi 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.
I'd need to investigate further the reason why they are doing like
that.
> gettadrinfo returns -8 which should be this:
> # define EAI_SERVICE -8 /* SERVICE not supported for `ai_socktype'. */
>
>
> I am not sure what is the most clever way to resolve this. Make SOCK_RAW
> branch out early and do the socket/bind(/listen) manually, use getaddrinfo
> twice with some more unspefici options, just deal with SOCK_RAW differently
> now? The attached code has the benefit of at least handling INET and INET6
> inside the getaddrinfo result.
>
> any ideas?
The quick thing would be to workaround libosmocore. I'll try to
investigate this issue a bit more but it may take me a while.
Hope it helps.