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: Willem de Bruijn <willemb@google.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h
index d3d715f8c..a4bb16f 100644
--- a/include/uapi/linux/if_packet.h
+++ b/include/uapi/linux/if_packet.h
@@ -55,6 +55,7 @@
#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 @@
#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
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index b5afe53..8869d07 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -92,6 +92,7 @@
#ifdef CONFIG_INET
#include <net/inet_common.h>
#endif
+#include <linux/bpf.h>
#include "internal.h"
@@ -1410,6 +1411,22 @@
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 @@
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 @@
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 @@
case PACKET_FANOUT_CPU:
case PACKET_FANOUT_RND:
case PACKET_FANOUT_QM:
+ case PACKET_FANOUT_CBPF:
break;
default:
return -EINVAL;
@@ -1561,10 +1650,10 @@
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 @@
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 @@
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;
diff --git a/net/packet/internal.h b/net/packet/internal.h
index e20b3e8..9ee4631 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -79,7 +79,10 @@
u16 id;
u8 type;
u8 flags;
- atomic_t rr_cur;
+ union {
+ atomic_t rr_cur;
+ struct bpf_prog __rcu *bpf_prog;
+ };
struct list_head list;
struct sock *arr[PACKET_FANOUT_MAX];
spinlock_t lock;