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packet: rollover huge flows before small flows

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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>
This commit is contained in:
Willem de Bruijn 2015-05-12 11:56:49 -04:00 committed by David S. Miller
parent 2ccdbaa6d5
commit 3b3a5b0aab
2 changed files with 24 additions and 3 deletions
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25
net/packet/af_packet.c
View File

@ -1341,6 +1341,20 @@ static int fanout_rr_next(struct packet_fanout *f, unsigned int num)
return x; 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, static unsigned int fanout_demux_hash(struct packet_fanout *f,
struct sk_buff *skb, struct sk_buff *skb,
unsigned int num) unsigned int num)
@ -1381,11 +1395,16 @@ static unsigned int fanout_demux_rollover(struct packet_fanout *f,
unsigned int num) unsigned int num)
{ {
struct packet_sock *po, *po_next; struct packet_sock *po, *po_next;
unsigned int i, j; unsigned int i, j, room;
po = pkt_sk(f->arr[idx]); 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); i = j = min_t(int, po->rollover->sock, num - 1);
do { do {

2
net/packet/internal.h
View File

@ -89,6 +89,8 @@ struct packet_fanout {
struct packet_rollover { struct packet_rollover {
int sock; int sock;
#define ROLLOVER_HLEN (L1_CACHE_BYTES / sizeof(u32))
u32 history[ROLLOVER_HLEN] ____cacheline_aligned;
} ____cacheline_aligned_in_smp; } ____cacheline_aligned_in_smp;
struct packet_sock { struct packet_sock {