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authorWillem de Bruijn <willemb@google.com>2015-05-12 11:56:49 -0400
committerDavid S. Miller <davem@davemloft.net>2015-05-13 15:43:00 -0400
commit3b3a5b0aab5b9ad345d4beb9a364a7dd02c23d40 (patch)
tree07714d34021e3505276c82d8c84c39324c4ddc97
parent2ccdbaa6d55b0656244ba57c4b56765a0af76c0a (diff)
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>
-rw-r--r--net/packet/af_packet.c25
-rw-r--r--net/packet/internal.h2
2 files changed, 24 insertions, 3 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 3a383fd72f82..8f0156b10f8d 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1341,6 +1341,20 @@ static int fanout_rr_next(struct packet_fanout *f, unsigned int num)
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 @@ static unsigned int fanout_demux_rollover(struct packet_fanout *f,
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 {
diff --git a/net/packet/internal.h b/net/packet/internal.h
index 22d7d778c5b7..a9d30a17c714 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -89,6 +89,8 @@ struct packet_fanout {
struct packet_rollover {
int sock;
+#define ROLLOVER_HLEN (L1_CACHE_BYTES / sizeof(u32))
+ u32 history[ROLLOVER_HLEN] ____cacheline_aligned;
} ____cacheline_aligned_in_smp;
struct packet_sock {