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Commit 47dceb8e authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

packet: add classic BPF fanout mode 



Add fanout mode PACKET_FANOUT_CBPF that accepts a classic BPF program
to select a socket.

This avoids having to keep adding special case fanout modes. One
example use case is application layer load balancing. The QUIC
protocol, for instance, encodes a connection ID in UDP payload.

Also add socket option SOL_PACKET/PACKET_FANOUT_DATA that updates data
associated with the socket group. Fanout mode PACKET_FANOUT_CBPF is the
only user so far.

Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a1c234f9

include/uapi/linux/if_packet.h

+2 −0
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ struct sockaddr_ll { 
#define PACKET_TX_HAS_OFF		19

#define PACKET_QDISC_BYPASS		20

#define PACKET_ROLLOVER_STATS		21

#define PACKET_FANOUT_DATA		22



#define PACKET_FANOUT_HASH		0

#define PACKET_FANOUT_LB		1
@@ -62,6 +63,7 @@ struct sockaddr_ll { 
#define PACKET_FANOUT_ROLLOVER		3

#define PACKET_FANOUT_RND		4

#define PACKET_FANOUT_QM		5

#define PACKET_FANOUT_CBPF		6

#define PACKET_FANOUT_FLAG_ROLLOVER	0x1000

#define PACKET_FANOUT_FLAG_DEFRAG	0x8000

net/packet/af_packet.c

+98 −1
Original line number Diff line number Diff line
@@ -92,6 +92,7 @@ 
#ifdef CONFIG_INET

#include <net/inet_common.h>

#endif

#include <linux/bpf.h>



#include "internal.h"
@@ -1410,6 +1411,22 @@ static unsigned int fanout_demux_qm(struct packet_fanout *f, 
	return skb_get_queue_mapping(skb) % num;

}



static unsigned int fanout_demux_bpf(struct packet_fanout *f,

				     struct sk_buff *skb,

				     unsigned int num)

{

	struct bpf_prog *prog;

	unsigned int ret = 0;



	rcu_read_lock();

	prog = rcu_dereference(f->bpf_prog);

	if (prog)

		ret = BPF_PROG_RUN(prog, skb) % num;

	rcu_read_unlock();



	return ret;

}



static bool fanout_has_flag(struct packet_fanout *f, u16 flag)

{

	return f->flags & (flag >> 8);
@@ -1454,6 +1471,9 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev, 
	case PACKET_FANOUT_ROLLOVER:

		idx = fanout_demux_rollover(f, skb, 0, false, num);

		break;

	case PACKET_FANOUT_CBPF:

		idx = fanout_demux_bpf(f, skb, num);

		break;

	}



	if (fanout_has_flag(f, PACKET_FANOUT_FLAG_ROLLOVER))
@@ -1502,6 +1522,74 @@ static bool match_fanout_group(struct packet_type *ptype, struct sock *sk) 
	return false;

}



static void fanout_init_data(struct packet_fanout *f)

{

	switch (f->type) {

	case PACKET_FANOUT_LB:

		atomic_set(&f->rr_cur, 0);

		break;

	case PACKET_FANOUT_CBPF:

		RCU_INIT_POINTER(f->bpf_prog, NULL);

		break;

	}

}



static void __fanout_set_data_bpf(struct packet_fanout *f, struct bpf_prog *new)

{

	struct bpf_prog *old;



	spin_lock(&f->lock);

	old = rcu_dereference_protected(f->bpf_prog, lockdep_is_held(&f->lock));

	rcu_assign_pointer(f->bpf_prog, new);

	spin_unlock(&f->lock);



	if (old) {

		synchronize_net();

		bpf_prog_destroy(old);

	}

}



static int fanout_set_data_cbpf(struct packet_sock *po, char __user *data,

				unsigned int len)

{

	struct bpf_prog *new;

	struct sock_fprog fprog;

	int ret;



	if (sock_flag(&po->sk, SOCK_FILTER_LOCKED))

		return -EPERM;

	if (len != sizeof(fprog))

		return -EINVAL;

	if (copy_from_user(&fprog, data, len))

		return -EFAULT;



	ret = bpf_prog_create_from_user(&new, &fprog, NULL);

	if (ret)

		return ret;



	__fanout_set_data_bpf(po->fanout, new);

	return 0;

}



static int fanout_set_data(struct packet_sock *po, char __user *data,

			   unsigned int len)

{

	switch (po->fanout->type) {

	case PACKET_FANOUT_CBPF:

		return fanout_set_data_cbpf(po, data, len);

	default:

		return -EINVAL;

	};

}



static void fanout_release_data(struct packet_fanout *f)

{

	switch (f->type) {

	case PACKET_FANOUT_CBPF:

		__fanout_set_data_bpf(f, NULL);

	};

}



static int fanout_add(struct sock *sk, u16 id, u16 type_flags)

{

	struct packet_sock *po = pkt_sk(sk);
@@ -1519,6 +1607,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) 
	case PACKET_FANOUT_CPU:

	case PACKET_FANOUT_RND:

	case PACKET_FANOUT_QM:

	case PACKET_FANOUT_CBPF:

		break;

	default:

		return -EINVAL;
@@ -1561,10 +1650,10 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) 
		match->id = id;

		match->type = type;

		match->flags = flags;

		atomic_set(&match->rr_cur, 0);

		INIT_LIST_HEAD(&match->list);

		spin_lock_init(&match->lock);

		atomic_set(&match->sk_ref, 0);

		fanout_init_data(match);

		match->prot_hook.type = po->prot_hook.type;

		match->prot_hook.dev = po->prot_hook.dev;

		match->prot_hook.func = packet_rcv_fanout;
@@ -1610,6 +1699,7 @@ static void fanout_release(struct sock *sk) 
	if (atomic_dec_and_test(&f->sk_ref)) {

		list_del(&f->list);

		dev_remove_pack(&f->prot_hook);

		fanout_release_data(f);

		kfree(f);

	}

	mutex_unlock(&fanout_mutex);
@@ -3529,6 +3619,13 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv 


		return fanout_add(sk, val & 0xffff, val >> 16);

	}

	case PACKET_FANOUT_DATA:

	{

		if (!po->fanout)

			return -EINVAL;



		return fanout_set_data(po, optval, optlen);

	}

	case PACKET_TX_HAS_OFF:

	{

		unsigned int val;

net/packet/internal.h

+4 −1
Original line number Diff line number Diff line
@@ -79,7 +79,10 @@ struct packet_fanout { 
	u16			id;

	u8			type;

	u8			flags;

	union {

		atomic_t		rr_cur;

		struct bpf_prog __rcu	*bpf_prog;

	};

	struct list_head	list;

	struct sock		*arr[PACKET_FANOUT_MAX];

	spinlock_t		lock;