net-tc: convert tc_from to tc_from_ingress and tc_redirected

The tc_from field fulfills two roles. It encodes whether a packet was
redirected by an act_mirred device and, if so, whether act_mirred was
called on ingress or egress. Split it into separate fields.

The information is needed by the special IFB loop, where packets are
taken out of the normal path by act_mirred, forwarded to IFB, then
reinjected at their original location (ingress or egress) by IFB.

The IFB device cannot use skb->tc_at_ingress, because that may have
been overwritten as the packet travels from act_mirred to ifb_xmit,
when it passes through tc_classify on the IFB egress path. Cache this
value in skb->tc_from_ingress.

That field is valid only if a packet arriving at ifb_xmit came from
act_mirred. Other packets can be crafted to reach ifb_xmit. These
must be dropped. Set tc_redirected on redirection and drop all packets
that do not have this bit set.

Both fields are set only on cloned skbs in tc actions, so original
packet sources do not have to clear the bit when reusing packets
(notably, pktgen and octeon).

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 8 deletions

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index b73b6b6c066b..312fce7302d3 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -78,9 +78,7 @@ static void ifb_ri_tasklet(unsigned long _txp)
 	}
 
 	while ((skb = __skb_dequeue(&txp->tq)) != NULL) {
-		u32 from = skb->tc_from;
-
-		skb_reset_tc(skb);
+		skb->tc_redirected = 0;
 		skb->tc_skip_classify = 1;
 
 		u64_stats_update_begin(&txp->tsync);
@@ -101,13 +99,12 @@ static void ifb_ri_tasklet(unsigned long _txp)
 		rcu_read_unlock();
 		skb->skb_iif = txp->dev->ifindex;
 
-		if (from & AT_EGRESS) {
+		if (!skb->tc_from_ingress) {
 			dev_queue_xmit(skb);
-		} else if (from & AT_INGRESS) {
+		} else {
 			skb_pull(skb, skb->mac_len);
 			netif_receive_skb(skb);
-		} else
-			BUG();
+		}
 	}
 
 	if (__netif_tx_trylock(txq)) {
@@ -246,7 +243,7 @@ static netdev_tx_t ifb_xmit(struct sk_buff *skb, struct net_device *dev)
 	txp->rx_bytes += skb->len;
 	u64_stats_update_end(&txp->rsync);
 
-	if (skb->tc_from == AT_STACK || !skb->skb_iif) {
+	if (!skb->tc_redirected || !skb->skb_iif) {
 		dev_kfree_skb(skb);
 		dev->stats.rx_dropped++;
 		return NETDEV_TX_OK;