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Re: [Qemu-devel] [PATCH] New feature - RFC3931 L2TPv3 network transport
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] New feature - RFC3931 L2TPv3 network transport using static Ethernet over L2TPv3 tunnels |
Date: |
Mon, 10 Mar 2014 09:35:31 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sun, Mar 09, 2014 at 05:06:15PM +0000, Anton Ivanov wrote:
> >>+ return -1;
> >>+ }
> >>+
> >>+ freeaddrinfo(result);
> >>+
> >>+ memset(&hints, 0, sizeof(hints));
> >>+
> >>+ if (s->ipv6) {
> >>+ hints.ai_family = AF_INET6;
> >>+ } else {
> >>+ hints.ai_family = AF_INET;
> >>+ }
> >>+ if (s->udp) {
> >>+ hints.ai_socktype = SOCK_DGRAM;
> >>+ hints.ai_protocol = 0;
> >>+ } else {
> >>+ hints.ai_socktype = SOCK_RAW;
> >>+ hints.ai_protocol = IPPROTO_L2TP;
> >Hang on, this is bogus. This is a *userspace* L2TP implementation!
> >
> >We don't want a kernel L2TP driver to handle this socket. Luckily this
> >never happens anyway since net/l2tp/l2tp_ip.c only registers its socket
> >type for <AF_INET, SOCK_DGRAM, IPPROTO_L2TP> and <AF_INET6, SOCK_DGRAM,
> >IPPROTO_L2TP>.
> >
> >When we create this socket with <AF_INET, SOCK_RAW, IPPROTO_L2TP> what
> >really happens is that the kernel falls back to the IPv4 raw socket
> >driver due to a wildcard match.
> >
> >In other words, we shouldn't use IPPROTO_L2TP. Just use 0.
> >
>
> This is not passed to socket directly - both setups share a call to
> getaddinfo() after that and use whatever it returns.
>
> If you pass family, RAW, 0 to getaddrinfo it returns family, DGRAM,
> 0. So when you use it later on the socket is setup incorrectly.
>
> If you pass RAW, PROTO_L2TPV3 it returns the correct values to setup
> the socket. Bug for bug canceling each other out :(
That doesn't match what I see. Can you double-check your test and figure out
what is happening?
Here is my test:
$ grep -r SOCK_RAW /usr/include/
/usr/include/bits/socket_type.h: SOCK_RAW = 3, /* Raw protocol interface. */
$ ./a
src ai_family 2 ai_socketype 3 ai_protocol 0
dst ai_family 2 ai_socketype 3 ai_protocol 0
$ cat a.c
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
int main(int argc, char **argv)
{
int fd, gairet;
struct addrinfo hints;
struct addrinfo * result = NULL;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_RAW;
hints.ai_protocol = 0;
gairet = getaddrinfo("localhost", NULL, &hints, &result);
if ((gairet !=0) || (result == NULL)) {
fprintf(stderr, "could not resolve src, errno = %s\n",
gai_strerror(gairet));
return 1;
}
printf("src ai_family %d ai_socketype %d ai_protocol %d\n",
result->ai_family, result->ai_socktype, result->ai_protocol);
freeaddrinfo(result);
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_RAW;
hints.ai_protocol = 0;
gairet = getaddrinfo("8.8.8.8", NULL, &hints, &result);
if ((gairet !=0) || (result == NULL)) {
fprintf(stderr, "could not resolve dst, errno = %s\n",
gai_strerror(gairet));
return 1;
}
printf("dst ai_family %d ai_socketype %d ai_protocol %d\n",
result->ai_family, result->ai_socktype, result->ai_protocol);
freeaddrinfo(result);
return 0;
}