packet: rollover huge flows before small flows
Migrate flows from a socket to another socket in the fanout group not
only when the socket is full. Start migrating huge flows early, to
divert possible 4-tuple attacks without affecting normal traffic.
Introduce fanout_flow_is_huge(). This detects huge flows, which are
defined as taking up more than half the load. It does so cheaply, by
storing the rxhashes of the N most recent packets. If over half of
these are the same rxhash as the current packet, then drop it. This
only protects against 4-tuple attacks. N is chosen to fit all data in
a single cache line.
Tested:
Ran bench_rollover for 10 sec with 1.5 Mpps of single flow input.
lpbb5:/export/hda3/willemb# ./bench_rollover -l 1000 -r -s
cpu rx rx.k drop.k rollover r.huge r.failed
0 14 14 0 0 0 0
1 20 20 0 0 0 0
2 16 16 0 0 0 0
3 6168824 6168824 0 4867721 4867721 0
4 4867741 4867741 0 0 0 0
5 12 12 0 0 0 0
6 15 15 0 0 0 0
7 17 17 0 0 0 0
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 3a383fd..8f0156b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1341,6 +1341,20 @@
return x;
}
+static bool fanout_flow_is_huge(struct packet_sock *po, struct sk_buff *skb)
+{
+ u32 rxhash;
+ int i, count = 0;
+
+ rxhash = skb_get_hash(skb);
+ for (i = 0; i < ROLLOVER_HLEN; i++)
+ if (po->rollover->history[i] == rxhash)
+ count++;
+
+ po->rollover->history[prandom_u32() % ROLLOVER_HLEN] = rxhash;
+ return count > (ROLLOVER_HLEN >> 1);
+}
+
static unsigned int fanout_demux_hash(struct packet_fanout *f,
struct sk_buff *skb,
unsigned int num)
@@ -1381,11 +1395,16 @@
unsigned int num)
{
struct packet_sock *po, *po_next;
- unsigned int i, j;
+ unsigned int i, j, room;
po = pkt_sk(f->arr[idx]);
- if (try_self && packet_rcv_has_room(po, skb) != ROOM_NONE)
- return idx;
+
+ if (try_self) {
+ room = packet_rcv_has_room(po, skb);
+ if (room == ROOM_NORMAL ||
+ (room == ROOM_LOW && !fanout_flow_is_huge(po, skb)))
+ return idx;
+ }
i = j = min_t(int, po->rollover->sock, num - 1);
do {