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authorWillem de Bruijn <willemb@google.com>2013-03-19 14:18:11 +0400
committerDavid S. Miller <davem@davemloft.net>2013-03-20 01:15:04 +0400
commit77f65ebdca506870d99bfabe52bde222511022ec (patch)
tree8f5ba6c76d1b49b44128d08281cc0b6f3e62285c /net/packet
parentb0aa73bf081da6810dacd750b9f8186640e172db (diff)
downloadlinux-77f65ebdca506870d99bfabe52bde222511022ec.tar.xz
packet: packet fanout rollover during socket overload
Changes: v3->v2: rebase (no other changes) passes selftest v2->v1: read f->num_members only once fix bug: test rollover mode + flag Minimize packet drop in a fanout group. If one socket is full, roll over packets to another from the group. Maintain flow affinity during normal load using an rxhash fanout policy, while dispersing unexpected traffic storms that hit a single cpu, such as spoofed-source DoS flows. Rollover breaks affinity for flows arriving at saturated sockets during those conditions. The patch adds a fanout policy ROLLOVER that rotates between sockets, filling each socket before moving to the next. It also adds a fanout flag ROLLOVER. If passed along with any other fanout policy, the primary policy is applied until the chosen socket is full. Then, rollover selects another socket, to delay packet drop until the entire system is saturated. Probing sockets is not free. Selecting the last used socket, as rollover does, is a greedy approach that maximizes chance of success, at the cost of extreme load imbalance. In practice, with sufficiently long queues to absorb bursts, sockets are drained in parallel and load balance looks uniform in `top`. To avoid contention, scales counters with number of sockets and accesses them lockfree. Values are bounds checked to ensure correctness. Tested using an application with 9 threads pinned to CPUs, one socket per thread and sufficient busywork per packet operation to limits each thread to handling 32 Kpps. When sent 500 Kpps single UDP stream packets, a FANOUT_CPU setup processes 32 Kpps in total without this patch, 270 Kpps with the patch. Tested with read() and with a packet ring (V1). Also, passes psock_fanout.c unit test added to selftests. Signed-off-by: Willem de Bruijn <willemb@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/packet')
-rw-r--r--net/packet/af_packet.c109
-rw-r--r--net/packet/internal.h3
2 files changed, 88 insertions, 24 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1d6793dbfbae..bd0d14c97d41 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -181,6 +181,8 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
struct packet_sock;
static int tpacket_snd(struct packet_sock *po, struct msghdr *msg);
+static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
+ struct packet_type *pt, struct net_device *orig_dev);
static void *packet_previous_frame(struct packet_sock *po,
struct packet_ring_buffer *rb,
@@ -973,11 +975,11 @@ static void *packet_current_rx_frame(struct packet_sock *po,
static void *prb_lookup_block(struct packet_sock *po,
struct packet_ring_buffer *rb,
- unsigned int previous,
+ unsigned int idx,
int status)
{
struct tpacket_kbdq_core *pkc = GET_PBDQC_FROM_RB(rb);
- struct tpacket_block_desc *pbd = GET_PBLOCK_DESC(pkc, previous);
+ struct tpacket_block_desc *pbd = GET_PBLOCK_DESC(pkc, idx);
if (status != BLOCK_STATUS(pbd))
return NULL;
@@ -1041,6 +1043,29 @@ static void packet_increment_head(struct packet_ring_buffer *buff)
buff->head = buff->head != buff->frame_max ? buff->head+1 : 0;
}
+static bool packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
+{
+ struct sock *sk = &po->sk;
+ bool has_room;
+
+ if (po->prot_hook.func != tpacket_rcv)
+ return (atomic_read(&sk->sk_rmem_alloc) + skb->truesize)
+ <= sk->sk_rcvbuf;
+
+ spin_lock(&sk->sk_receive_queue.lock);
+ if (po->tp_version == TPACKET_V3)
+ has_room = prb_lookup_block(po, &po->rx_ring,
+ po->rx_ring.prb_bdqc.kactive_blk_num,
+ TP_STATUS_KERNEL);
+ else
+ has_room = packet_lookup_frame(po, &po->rx_ring,
+ po->rx_ring.head,
+ TP_STATUS_KERNEL);
+ spin_unlock(&sk->sk_receive_queue.lock);
+
+ return has_room;
+}
+
static void packet_sock_destruct(struct sock *sk)
{
skb_queue_purge(&sk->sk_error_queue);
@@ -1066,16 +1091,16 @@ static int fanout_rr_next(struct packet_fanout *f, unsigned int num)
return x;
}
-static struct sock *fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
+static unsigned int fanout_demux_hash(struct packet_fanout *f,
+ struct sk_buff *skb,
+ unsigned int num)
{
- u32 idx, hash = skb->rxhash;
-
- idx = ((u64)hash * num) >> 32;
-
- return f->arr[idx];
+ return (((u64)skb->rxhash) * num) >> 32;
}
-static struct sock *fanout_demux_lb(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
+static unsigned int fanout_demux_lb(struct packet_fanout *f,
+ struct sk_buff *skb,
+ unsigned int num)
{
int cur, old;
@@ -1083,14 +1108,40 @@ static struct sock *fanout_demux_lb(struct packet_fanout *f, struct sk_buff *skb
while ((old = atomic_cmpxchg(&f->rr_cur, cur,
fanout_rr_next(f, num))) != cur)
cur = old;
- return f->arr[cur];
+ return cur;
+}
+
+static unsigned int fanout_demux_cpu(struct packet_fanout *f,
+ struct sk_buff *skb,
+ unsigned int num)
+{
+ return smp_processor_id() % num;
}
-static struct sock *fanout_demux_cpu(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
+static unsigned int fanout_demux_rollover(struct packet_fanout *f,
+ struct sk_buff *skb,
+ unsigned int idx, unsigned int skip,
+ unsigned int num)
{
- unsigned int cpu = smp_processor_id();
+ unsigned int i, j;
- return f->arr[cpu % num];
+ i = j = min_t(int, f->next[idx], num - 1);
+ do {
+ if (i != skip && packet_rcv_has_room(pkt_sk(f->arr[i]), skb)) {
+ if (i != j)
+ f->next[idx] = i;
+ return i;
+ }
+ if (++i == num)
+ i = 0;
+ } while (i != j);
+
+ return idx;
+}
+
+static bool fanout_has_flag(struct packet_fanout *f, u16 flag)
+{
+ return f->flags & (flag >> 8);
}
static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
@@ -1099,7 +1150,7 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
struct packet_fanout *f = pt->af_packet_priv;
unsigned int num = f->num_members;
struct packet_sock *po;
- struct sock *sk;
+ unsigned int idx;
if (!net_eq(dev_net(dev), read_pnet(&f->net)) ||
!num) {
@@ -1110,23 +1161,31 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
switch (f->type) {
case PACKET_FANOUT_HASH:
default:
- if (f->defrag) {
+ if (fanout_has_flag(f, PACKET_FANOUT_FLAG_DEFRAG)) {
skb = ip_check_defrag(skb, IP_DEFRAG_AF_PACKET);
if (!skb)
return 0;
}
skb_get_rxhash(skb);
- sk = fanout_demux_hash(f, skb, num);
+ idx = fanout_demux_hash(f, skb, num);
break;
case PACKET_FANOUT_LB:
- sk = fanout_demux_lb(f, skb, num);
+ idx = fanout_demux_lb(f, skb, num);
break;
case PACKET_FANOUT_CPU:
- sk = fanout_demux_cpu(f, skb, num);
+ idx = fanout_demux_cpu(f, skb, num);
+ break;
+ case PACKET_FANOUT_ROLLOVER:
+ idx = fanout_demux_rollover(f, skb, 0, (unsigned int) -1, num);
break;
}
- po = pkt_sk(sk);
+ po = pkt_sk(f->arr[idx]);
+ if (fanout_has_flag(f, PACKET_FANOUT_FLAG_ROLLOVER) &&
+ unlikely(!packet_rcv_has_room(po, skb))) {
+ idx = fanout_demux_rollover(f, skb, idx, idx, num);
+ po = pkt_sk(f->arr[idx]);
+ }
return po->prot_hook.func(skb, dev, &po->prot_hook, orig_dev);
}
@@ -1175,10 +1234,13 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
struct packet_sock *po = pkt_sk(sk);
struct packet_fanout *f, *match;
u8 type = type_flags & 0xff;
- u8 defrag = (type_flags & PACKET_FANOUT_FLAG_DEFRAG) ? 1 : 0;
+ u8 flags = type_flags >> 8;
int err;
switch (type) {
+ case PACKET_FANOUT_ROLLOVER:
+ if (type_flags & PACKET_FANOUT_FLAG_ROLLOVER)
+ return -EINVAL;
case PACKET_FANOUT_HASH:
case PACKET_FANOUT_LB:
case PACKET_FANOUT_CPU:
@@ -1203,7 +1265,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
}
}
err = -EINVAL;
- if (match && match->defrag != defrag)
+ if (match && match->flags != flags)
goto out;
if (!match) {
err = -ENOMEM;
@@ -1213,7 +1275,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
write_pnet(&match->net, sock_net(sk));
match->id = id;
match->type = type;
- match->defrag = defrag;
+ match->flags = flags;
atomic_set(&match->rr_cur, 0);
INIT_LIST_HEAD(&match->list);
spin_lock_init(&match->lock);
@@ -3240,7 +3302,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
case PACKET_FANOUT:
val = (po->fanout ?
((u32)po->fanout->id |
- ((u32)po->fanout->type << 16)) :
+ ((u32)po->fanout->type << 16) |
+ ((u32)po->fanout->flags << 24)) :
0);
break;
case PACKET_TX_HAS_OFF:
diff --git a/net/packet/internal.h b/net/packet/internal.h
index e84cab8cb7a9..e891f025a1b9 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -77,10 +77,11 @@ struct packet_fanout {
unsigned int num_members;
u16 id;
u8 type;
- u8 defrag;
+ u8 flags;
atomic_t rr_cur;
struct list_head list;
struct sock *arr[PACKET_FANOUT_MAX];
+ int next[PACKET_FANOUT_MAX];
spinlock_t lock;
atomic_t sk_ref;
struct packet_type prot_hook ____cacheline_aligned_in_smp;