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af_packet: don't emit packet on orig fanout group
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If a packet is emitted on one socket in one group of fanout sockets,
it is transmitted again. It is thus read again on one of the sockets
of the fanout group. This result in a loop for software which
generate packets when receiving one.
This retransmission is not the intended behavior: a fanout group
must behave like a single socket. The packet should not be
transmitted on a socket if it originates from a socket belonging
to the same fanout group.

This patch fixes the issue by changing the transmission check to
take fanout group info account.

Reported-by: Aleksandr Kotov <[email protected]>
Signed-off-by: Eric Leblond <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
regit authored and davem330 committed Aug 20, 2012
1 parent 9915e67 commit c0de08d
Showing 3 changed files with 25 additions and 2 deletions.
2 changes: 2 additions & 0 deletions include/linux/netdevice.h
Original file line number Diff line number Diff line change
@@ -1522,6 +1522,8 @@ struct packet_type {
struct sk_buff **(*gro_receive)(struct sk_buff **head,
struct sk_buff *skb);
int (*gro_complete)(struct sk_buff *skb);
bool (*id_match)(struct packet_type *ptype,
struct sock *sk);
void *af_packet_priv;
struct list_head list;
};
16 changes: 14 additions & 2 deletions net/core/dev.c
Original file line number Diff line number Diff line change
@@ -1642,6 +1642,19 @@ static inline int deliver_skb(struct sk_buff *skb,
return pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
}

static inline bool skb_loop_sk(struct packet_type *ptype, struct sk_buff *skb)
{
if (ptype->af_packet_priv == NULL)
return false;

if (ptype->id_match)
return ptype->id_match(ptype, skb->sk);
else if ((struct sock *)ptype->af_packet_priv == skb->sk)
return true;

return false;
}

/*
* Support routine. Sends outgoing frames to any network
* taps currently in use.
@@ -1659,8 +1672,7 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
* they originated from - MvS ([email protected])
*/
if ((ptype->dev == dev || !ptype->dev) &&
(ptype->af_packet_priv == NULL ||
(struct sock *)ptype->af_packet_priv != skb->sk)) {
(!skb_loop_sk(ptype, skb))) {
if (pt_prev) {
deliver_skb(skb2, pt_prev, skb->dev);
pt_prev = ptype;
9 changes: 9 additions & 0 deletions net/packet/af_packet.c
Original file line number Diff line number Diff line change
@@ -1273,6 +1273,14 @@ static void __fanout_unlink(struct sock *sk, struct packet_sock *po)
spin_unlock(&f->lock);
}

bool match_fanout_group(struct packet_type *ptype, struct sock * sk)
{
if (ptype->af_packet_priv == (void*)((struct packet_sock *)sk)->fanout)
return true;

return false;
}

static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
{
struct packet_sock *po = pkt_sk(sk);
@@ -1325,6 +1333,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
match->prot_hook.dev = po->prot_hook.dev;
match->prot_hook.func = packet_rcv_fanout;
match->prot_hook.af_packet_priv = match;
match->prot_hook.id_match = match_fanout_group;
dev_add_pack(&match->prot_hook);
list_add(&match->list, &fanout_list);
}

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