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packet: Add fanout support.
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Fanouts allow packet capturing to be demuxed to a set of AF_PACKET
sockets.  Two fanout policies are implemented:

1) Hashing based upon skb->rxhash

2) Pure round-robin

An AF_PACKET socket must be fully bound before it tries to add itself
to a fanout.  All AF_PACKET sockets trying to join the same fanout
must all have the same bind settings.

Fanouts are identified (within a network namespace) by a 16-bit ID.
The first socket to try to add itself to a fanout with a particular
ID, creates that fanout.  When the last socket leaves the fanout
(which happens only when the socket is closed), that fanout is
destroyed.

Signed-off-by: David S. Miller <davem@davemloft.net>
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@davem330
davem330 committed Jul 6, 2011
1 parent ce06b03 commit dc99f60
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Showing 2 changed files with 255 additions and 5 deletions.
4 changes: 4 additions & 0 deletions include/linux/if_packet.h
View file
Expand Up @@ -49,6 +49,10 @@ struct sockaddr_ll {
#define PACKET_VNET_HDR 15
#define PACKET_TX_TIMESTAMP 16
#define PACKET_TIMESTAMP 17
#define PACKET_FANOUT 18

#define PACKET_FANOUT_HASH 0
#define PACKET_FANOUT_LB 1

struct tpacket_stats {
unsigned int tp_packets;
Expand Down
256 changes: 251 additions & 5 deletions net/packet/af_packet.c
View file
Expand Up @@ -187,9 +187,11 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg);

static void packet_flush_mclist(struct sock *sk);

struct packet_fanout;
struct packet_sock {
/* struct sock has to be the first member of packet_sock */
struct sock sk;
struct packet_fanout *fanout;
struct tpacket_stats stats;
struct packet_ring_buffer rx_ring;
struct packet_ring_buffer tx_ring;
Expand All @@ -212,6 +214,24 @@ struct packet_sock {
struct packet_type prot_hook ____cacheline_aligned_in_smp;
};

#define PACKET_FANOUT_MAX 256

struct packet_fanout {
#ifdef CONFIG_NET_NS
struct net *net;
#endif
unsigned int num_members;
u16 id;
u8 type;
u8 pad;
atomic_t rr_cur;
struct list_head list;
struct sock *arr[PACKET_FANOUT_MAX];
spinlock_t lock;
atomic_t sk_ref;
struct packet_type prot_hook ____cacheline_aligned_in_smp;
};

struct packet_skb_cb {
unsigned int origlen;
union {
Expand All @@ -227,6 +247,9 @@ static inline struct packet_sock *pkt_sk(struct sock *sk)
return (struct packet_sock *)sk;
}

static void __fanout_unlink(struct sock *sk, struct packet_sock *po);
static void __fanout_link(struct sock *sk, struct packet_sock *po);

/* register_prot_hook must be invoked with the po->bind_lock held,
* or from a context in which asynchronous accesses to the packet
* socket is not possible (packet_create()).
Expand All @@ -235,7 +258,10 @@ static void register_prot_hook(struct sock *sk)
{
struct packet_sock *po = pkt_sk(sk);
if (!po->running) {
dev_add_pack(&po->prot_hook);
if (po->fanout)
__fanout_link(sk, po);
else
dev_add_pack(&po->prot_hook);
sock_hold(sk);
po->running = 1;
}
Expand All @@ -253,7 +279,10 @@ static void __unregister_prot_hook(struct sock *sk, bool sync)
struct packet_sock *po = pkt_sk(sk);

po->running = 0;
__dev_remove_pack(&po->prot_hook);
if (po->fanout)
__fanout_unlink(sk, po);
else
__dev_remove_pack(&po->prot_hook);
__sock_put(sk);

if (sync) {
Expand Down Expand Up @@ -388,6 +417,201 @@ static void packet_sock_destruct(struct sock *sk)
sk_refcnt_debug_dec(sk);
}

static int fanout_rr_next(struct packet_fanout *f, unsigned int num)
{
int x = atomic_read(&f->rr_cur) + 1;

if (x >= num)
x = 0;

return x;
}

static struct sock *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];
}

static struct sock *fanout_demux_lb(struct packet_fanout *f, struct sk_buff *skb, unsigned int num)
{
int cur, old;

cur = atomic_read(&f->rr_cur);
while ((old = atomic_cmpxchg(&f->rr_cur, cur,
fanout_rr_next(f, num))) != cur)
cur = old;
return f->arr[cur];
}

static int packet_rcv_fanout_hash(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
struct packet_fanout *f = pt->af_packet_priv;
unsigned int num = f->num_members;
struct packet_sock *po;
struct sock *sk;

if (!net_eq(dev_net(dev), read_pnet(&f->net)) ||
!num) {
kfree_skb(skb);
return 0;
}

skb_get_rxhash(skb);

sk = fanout_demux_hash(f, skb, num);
po = pkt_sk(sk);

return po->prot_hook.func(skb, dev, &po->prot_hook, orig_dev);
}

static int packet_rcv_fanout_lb(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
struct packet_fanout *f = pt->af_packet_priv;
unsigned int num = f->num_members;
struct packet_sock *po;
struct sock *sk;

if (!net_eq(dev_net(dev), read_pnet(&f->net)) ||
!num) {
kfree_skb(skb);
return 0;
}

sk = fanout_demux_lb(f, skb, num);
po = pkt_sk(sk);

return po->prot_hook.func(skb, dev, &po->prot_hook, orig_dev);
}

static DEFINE_MUTEX(fanout_mutex);
static LIST_HEAD(fanout_list);

static void __fanout_link(struct sock *sk, struct packet_sock *po)
{
struct packet_fanout *f = po->fanout;

spin_lock(&f->lock);
f->arr[f->num_members] = sk;
smp_wmb();
f->num_members++;
spin_unlock(&f->lock);
}

static void __fanout_unlink(struct sock *sk, struct packet_sock *po)
{
struct packet_fanout *f = po->fanout;
int i;

spin_lock(&f->lock);
for (i = 0; i < f->num_members; i++) {
if (f->arr[i] == sk)
break;
}
BUG_ON(i >= f->num_members);
f->arr[i] = f->arr[f->num_members - 1];
f->num_members--;
spin_unlock(&f->lock);
}

static int fanout_add(struct sock *sk, u16 id, u8 type)
{
struct packet_sock *po = pkt_sk(sk);
struct packet_fanout *f, *match;
int err;

switch (type) {
case PACKET_FANOUT_HASH:
case PACKET_FANOUT_LB:
break;
default:
return -EINVAL;
}

if (!po->running)
return -EINVAL;

if (po->fanout)
return -EALREADY;

mutex_lock(&fanout_mutex);
match = NULL;
list_for_each_entry(f, &fanout_list, list) {
if (f->id == id &&
read_pnet(&f->net) == sock_net(sk)) {
match = f;
break;
}
}
if (!match) {
match = kzalloc(sizeof(*match), GFP_KERNEL);
if (match) {
write_pnet(&match->net, sock_net(sk));
match->id = id;
match->type = type;
atomic_set(&match->rr_cur, 0);
INIT_LIST_HEAD(&match->list);
spin_lock_init(&match->lock);
atomic_set(&match->sk_ref, 0);
match->prot_hook.type = po->prot_hook.type;
match->prot_hook.dev = po->prot_hook.dev;
switch (type) {
case PACKET_FANOUT_HASH:
match->prot_hook.func = packet_rcv_fanout_hash;
break;
case PACKET_FANOUT_LB:
match->prot_hook.func = packet_rcv_fanout_lb;
break;
}
match->prot_hook.af_packet_priv = match;
dev_add_pack(&match->prot_hook);
list_add(&match->list, &fanout_list);
}
}
err = -ENOMEM;
if (match) {
err = -EINVAL;
if (match->type == type &&
match->prot_hook.type == po->prot_hook.type &&
match->prot_hook.dev == po->prot_hook.dev) {
err = -ENOSPC;
if (atomic_read(&match->sk_ref) < PACKET_FANOUT_MAX) {
__dev_remove_pack(&po->prot_hook);
po->fanout = match;
atomic_inc(&match->sk_ref);
__fanout_link(sk, po);
err = 0;
}
}
}
mutex_unlock(&fanout_mutex);
return err;
}

static void fanout_release(struct sock *sk)
{
struct packet_sock *po = pkt_sk(sk);
struct packet_fanout *f;

f = po->fanout;
if (!f)
return;

po->fanout = NULL;

mutex_lock(&fanout_mutex);
if (atomic_dec_and_test(&f->sk_ref)) {
list_del(&f->list);
dev_remove_pack(&f->prot_hook);
kfree(f);
}
mutex_unlock(&fanout_mutex);
}

static const struct proto_ops packet_ops;

Expand Down Expand Up @@ -1398,6 +1622,8 @@ static int packet_release(struct socket *sock)
if (po->tx_ring.pg_vec)
packet_set_ring(sk, &req, 1, 1);

fanout_release(sk);

synchronize_net();
/*
* Now the socket is dead. No more input will appear.
Expand All @@ -1421,9 +1647,9 @@ static int packet_release(struct socket *sock)
static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 protocol)
{
struct packet_sock *po = pkt_sk(sk);
/*
* Detach an existing hook if present.
*/

if (po->fanout)
return -EINVAL;

lock_sock(sk);

Expand Down Expand Up @@ -2133,6 +2359,17 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
po->tp_tstamp = val;
return 0;
}
case PACKET_FANOUT:
{
int val;

if (optlen != sizeof(val))
return -EINVAL;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;

return fanout_add(sk, val & 0xffff, val >> 16);
}
default:
return -ENOPROTOOPT;
}
Expand Down Expand Up @@ -2231,6 +2468,15 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
val = po->tp_tstamp;
data = &val;
break;
case PACKET_FANOUT:
if (len > sizeof(int))
len = sizeof(int);
val = (po->fanout ?
((u32)po->fanout->id |
((u32)po->fanout->type << 16)) :
0);
data = &val;
break;
default:
return -ENOPROTOOPT;
}
Expand Down

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