On 27 October 2015 at 03:09, Laurent Vivier <laur...@vivier.eu> wrote:
> Le 26/10/2015 15:40, Peter Maydell a écrit :
>> This confuses me. The packet(7) manpage suggests there are two flavours
>> of packet socket:
>> (1) legacy AF_INET + SOCK_PACKET
>> (2) new style AF_PACKET + SOCK_RAW / SOCK_DGRAM
>>
>> but this comment suggests it's trying to handle AF_PACKET + SOCK_PACKET ?
>
> In fact, I've started not from the man page, but from a non working dhcp
> client, originally with a m68k target and etch-m68k distro, and I've met
> again this problem on a ppc target and jessie distro.
> kernel 4.3.0-rc3, net/packet/af_packet.c:
>
> 2961
> 2962 static int packet_bind_spkt(struct socket *sock, struct sockaddr
> *uaddr,
> 2963 int addr_len)
> 2964 {
> 2965 struct sock *sk = sock->sk;
> 2966 char name[15];
> 2967 struct net_device *dev;
> 2968 int err = -ENODEV;
> 2969
> 2970 /*
> 2971 * Check legality
> 2972 */
> 2973
> 2974 if (addr_len != sizeof(struct sockaddr))
> 2975 return -EINVAL;
> 2976 strlcpy(name, uaddr->sa_data, sizeof(name));
> 2977
> 2978 dev = dev_get_by_name(sock_net(sk), name);
> 2979 if (dev)
> 2980 err = packet_do_bind(sk, dev, pkt_sk(sk)->num);
> 2981 return err;
> 2982 }
> ...
> 4246 static const struct proto_ops packet_ops_spkt = {
> 4247 .family = PF_PACKET,
> ...
> 4250 .bind = packet_bind_spkt,
> ...
> 3022
> 3023 static int packet_create(struct net *net, struct socket *sock,
> int protocol,
> 3024 int kern)
> ...
> 3045 if (sock->type == SOCK_PACKET)
> 3046 sock->ops = &packet_ops_spkt;
> ...
Yes, but also:
http://lxr.free-electrons.com/source/net/socket.c#L1109
1114 if (family == PF_INET && type == SOCK_PACKET) {
1115 static int warned;
1116 if (!warned) {
1117 warned = 1;
1118 pr_info("%s uses obsolete (PF_INET,SOCK_PACKET)\n",
1119 current->comm);
1120 }
1121 family = PF_PACKET;
1122 }
So I think my conclusion is:
* Original 2.0 kernels used PF_INET + SOCK_PACKET
* When the non-legacy stuff was added and this compat warning
came in, the (accidental?) result was that PF_PACKET + SOCK_PACKET
gave a warning, PF_PACKET + SOCK_PACKET gave legacy behaviour
without a warning, and PF_PACKET + SOCK_RAW/SOCK_DGRAM gave
the new interface
* Some userspace programs responded not by updating to the new
non-legacy interface, but by moving to PF_PACKET + SOCK_PACKET
which just suppresses the warning
So we should special case both PF_INET + SOCK_PACKET and
PF_PACKET + SOCK_PACKET (but not any other PF_* + SOCK_PACKET).
thanks
-- PMM
