Commit d9850f8e authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Luis Henriques

packet: infer protocol from ethernet header if unset

commit c72219b7 upstream.

In case no struct sockaddr_ll has been passed to packet
socket's sendmsg() when doing a TX_RING flush run, then
skb->protocol is set to po->num instead, which is the protocol
passed via socket(2)/bind(2).

Applications only xmitting can go the path of allocating the
socket as socket(PF_PACKET, <mode>, 0) and do a bind(2) on the
TX_RING with sll_protocol of 0. That way, register_prot_hook()
is neither called on creation nor on bind time, which saves
cycles when there's no interest in capturing anyway.

That leaves us however with po->num 0 instead and therefore
the TX_RING flush run sets skb->protocol to 0 as well. Eric
reported that this leads to problems when using tools like
trafgen over bonding device. I.e. the bonding's hash function
could invoke the kernel's flow dissector, which depends on
skb->protocol being properly set. In the current situation, all
the traffic is then directed to a single slave.

Fix it up by inferring skb->protocol from the Ethernet header
when not set and we have ARPHRD_ETHER device type. This is only
done in case of SOCK_RAW and where we have a dev->hard_header_len
length. In case of ARPHRD_ETHER devices, this is guaranteed to
cover ETH_HLEN, and therefore being accessed on the skb after
the skb_store_bits().
Reported-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 66a74d96
...@@ -2097,6 +2097,15 @@ static void tpacket_destruct_skb(struct sk_buff *skb) ...@@ -2097,6 +2097,15 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
sock_wfree(skb); sock_wfree(skb);
} }
static void tpacket_set_protocol(const struct net_device *dev,
struct sk_buff *skb)
{
if (dev->type == ARPHRD_ETHER) {
skb_reset_mac_header(skb);
skb->protocol = eth_hdr(skb)->h_proto;
}
}
static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb, static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
void *frame, struct net_device *dev, int size_max, void *frame, struct net_device *dev, int size_max,
__be16 proto, unsigned char *addr, int hlen) __be16 proto, unsigned char *addr, int hlen)
...@@ -2182,6 +2191,8 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb, ...@@ -2182,6 +2191,8 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
dev->hard_header_len); dev->hard_header_len);
if (unlikely(err)) if (unlikely(err))
return err; return err;
if (!skb->protocol)
tpacket_set_protocol(dev, skb);
data += dev->hard_header_len; data += dev->hard_header_len;
to_write -= dev->hard_header_len; to_write -= dev->hard_header_len;
......
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