bpf: sockmap with sk redirect support

Recently we added a new map type called dev map used to forward XDP
packets between ports (6093ec2d). This patches introduces a
similar notion for sockets.

A sockmap allows users to add participating sockets to a map. When
sockets are added to the map enough context is stored with the
map entry to use the entry with a new helper

  bpf_sk_redirect_map(map, key, flags)

This helper (analogous to bpf_redirect_map in XDP) is given the map
and an entry in the map. When called from a sockmap program, discussed
below, the skb will be sent on the socket using skb_send_sock().

With the above we need a bpf program to call the helper from that will
then implement the send logic. The initial site implemented in this
series is the recv_sock hook. For this to work we implemented a map
attach command to add attributes to a map. In sockmap we add two
programs a parse program and a verdict program. The parse program
uses strparser to build messages and pass them to the verdict program.
The parse programs use the normal strparser semantics. The verdict
program is of type SK_SKB.

The verdict program returns a verdict SK_DROP, or  SK_REDIRECT for
now. Additional actions may be added later. When SK_REDIRECT is
returned, expected when bpf program uses bpf_sk_redirect_map(), the
sockmap logic will consult per cpu variables set by the helper routine
and pull the sock entry out of the sock map. This pattern follows the
existing redirect logic in cls and xdp programs.

This gives the flow,

 recv_sock -> str_parser (parse_prog) -> verdict_prog -> skb_send_sock
                                                     \
                                                      -> kfree_skb

As an example use case a message based load balancer may use specific
logic in the verdict program to select the sock to send on.

Sample programs are provided in future patches that hopefully illustrate
the user interfaces. Also selftests are in follow-on patches.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/bpf.h

@@ -16,6 +16,7 @@
 #include <linux/rbtree_latch.h>
 
 struct perf_event;
+struct bpf_prog;
 struct bpf_map;
 
 /* map is generic key/value storage optionally accesible by eBPF programs */
@@ -37,6 +38,8 @@ struct bpf_map_ops {
 	void (*map_fd_put_ptr)(void *ptr);
 	u32 (*map_gen_lookup)(struct bpf_map *map, struct bpf_insn *insn_buf);
 	u32 (*map_fd_sys_lookup_elem)(void *ptr);
+	int (*map_attach)(struct bpf_map *map,
+			  struct bpf_prog *p1, struct bpf_prog *p2);
 };
 
 struct bpf_map {
@@ -138,8 +141,6 @@ enum bpf_reg_type {
 	PTR_TO_PACKET_END,	 /* skb->data + headlen */
 };
 
-struct bpf_prog;
-
 /* The information passed from prog-specific *_is_valid_access
  * back to the verifier.
  */
@@ -312,6 +313,7 @@ int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
 
 /* Map specifics */
 struct net_device  *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
+struct sock  *__sock_map_lookup_elem(struct bpf_map *map, u32 key);
 void __dev_map_insert_ctx(struct bpf_map *map, u32 index);
 void __dev_map_flush(struct bpf_map *map);
 
@@ -391,6 +393,7 @@ extern const struct bpf_func_proto bpf_get_current_comm_proto;
 extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
 extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
 extern const struct bpf_func_proto bpf_get_stackid_proto;
+extern const struct bpf_func_proto bpf_sock_map_update_proto;
 
 /* Shared helpers among cBPF and eBPF. */
 void bpf_user_rnd_init_once(void);

include/linux/bpf_types.h

@@ -38,4 +38,5 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY_OF_MAPS, array_of_maps_map_ops)
 BPF_MAP_TYPE(BPF_MAP_TYPE_HASH_OF_MAPS, htab_of_maps_map_ops)
 #ifdef CONFIG_NET
 BPF_MAP_TYPE(BPF_MAP_TYPE_DEVMAP, dev_map_ops)
+BPF_MAP_TYPE(BPF_MAP_TYPE_SOCKMAP, sock_map_ops)
 #endif

include/linux/filter.h

@@ -727,6 +727,8 @@ void xdp_do_flush_map(void);
 void bpf_warn_invalid_xdp_action(u32 act);
 void bpf_warn_invalid_xdp_redirect(u32 ifindex);
 
+struct sock *do_sk_redirect_map(void);
+
 #ifdef CONFIG_BPF_JIT
 extern int bpf_jit_enable;
 extern int bpf_jit_harden;

include/uapi/linux/bpf.h

@@ -110,6 +110,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_ARRAY_OF_MAPS,
 	BPF_MAP_TYPE_HASH_OF_MAPS,
 	BPF_MAP_TYPE_DEVMAP,
+	BPF_MAP_TYPE_SOCKMAP,
 };
 
 enum bpf_prog_type {
@@ -135,11 +136,15 @@ enum bpf_attach_type {
 	BPF_CGROUP_INET_EGRESS,
 	BPF_CGROUP_INET_SOCK_CREATE,
 	BPF_CGROUP_SOCK_OPS,
+	BPF_CGROUP_SMAP_INGRESS,
 	__MAX_BPF_ATTACH_TYPE
 };
 
 #define MAX_BPF_ATTACH_TYPE __MAX_BPF_ATTACH_TYPE
 
+/* If BPF_SOCKMAP_STRPARSER is used sockmap will use strparser on receive */
+#define BPF_SOCKMAP_STRPARSER	(1U << 0)
+
 /* If BPF_F_ALLOW_OVERRIDE flag is used in BPF_PROG_ATTACH command
  * to the given target_fd cgroup the descendent cgroup will be able to
  * override effective bpf program that was inherited from this cgroup
@@ -211,6 +216,7 @@ union bpf_attr {
 		__u32		attach_bpf_fd;	/* eBPF program to attach */
 		__u32		attach_type;
 		__u32		attach_flags;
+		__u32		attach_bpf_fd2;
 	};
 
 	struct { /* anonymous struct used by BPF_PROG_TEST_RUN command */
@@ -557,6 +563,23 @@ union bpf_attr {
  *     @mode: operation mode (enum bpf_adj_room_mode)
  *     @flags: reserved for future use
  *     Return: 0 on success or negative error code
+ *
+ * int bpf_sk_redirect_map(map, key, flags)
+ *     Redirect skb to a sock in map using key as a lookup key for the
+ *     sock in map.
+ *     @map: pointer to sockmap
+ *     @key: key to lookup sock in map
+ *     @flags: reserved for future use
+ *     Return: SK_REDIRECT
+ *
+ * int bpf_sock_map_update(skops, map, key, flags, map_flags)
+ *	@skops: pointer to bpf_sock_ops
+ *	@map: pointer to sockmap to update
+ *	@key: key to insert/update sock in map
+ *	@flags: same flags as map update elem
+ *	@map_flags: sock map specific flags
+ *	   bit 1: Enable strparser
+ *	   other bits: reserved
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -610,7 +633,9 @@ union bpf_attr {
 	FN(set_hash),			\
 	FN(setsockopt),			\
 	FN(skb_adjust_room),		\
-	FN(redirect_map),
+	FN(redirect_map),		\
+	FN(sk_redirect_map),		\
+	FN(sock_map_update),		\
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -747,6 +772,12 @@ struct xdp_md {
 	__u32 data_end;
 };
 
+enum sk_action {
+	SK_ABORTED = 0,
+	SK_DROP,
+	SK_REDIRECT,
+};
+
 #define BPF_TAG_SIZE	8
 
 struct bpf_prog_info {

kernel/bpf/Makefile

@@ -3,7 +3,7 @@ obj-y := core.o
 obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
 ifeq ($(CONFIG_NET),y)
-obj-$(CONFIG_BPF_SYSCALL) += devmap.o
+obj-$(CONFIG_BPF_SYSCALL) += devmap.o sockmap.o
 endif
 ifeq ($(CONFIG_PERF_EVENTS),y)
 obj-$(CONFIG_BPF_SYSCALL) += stackmap.o

kernel/bpf/sockmap.c

+/* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+/* A BPF sock_map is used to store sock objects. This is primarly used
+ * for doing socket redirect with BPF helper routines.
+ *
+ * A sock map may have two BPF programs attached to it, a program used
+ * to parse packets and a program to provide a verdict and redirect
+ * decision on the packet. If no BPF parse program is provided it is
+ * assumed that every skb is a "message" (skb->len). Otherwise the
+ * parse program is attached to strparser and used to build messages
+ * that may span multiple skbs. The verdict program will either select
+ * a socket to send/receive the skb on or provide the drop code indicating
+ * the skb should be dropped. More actions may be added later as needed.
+ * The default program will drop packets.
+ *
+ * For reference this program is similar to devmap used in XDP context
+ * reviewing these together may be useful. For an example please review
+ * ./samples/bpf/sockmap/.
+ */
+#include <linux/bpf.h>
+#include <net/sock.h>
+#include <linux/filter.h>
+#include <linux/errno.h>
+#include <linux/file.h>
+#include <linux/kernel.h>
+#include <linux/net.h>
+#include <linux/skbuff.h>
+#include <linux/workqueue.h>
+#include <linux/list.h>
+#include <net/strparser.h>
+
+struct bpf_stab {
+	struct bpf_map map;
+	struct sock **sock_map;
+	struct bpf_prog *bpf_parse;
+	struct bpf_prog *bpf_verdict;
+	refcount_t refcnt;
+};
+
+enum smap_psock_state {
+	SMAP_TX_RUNNING,
+};
+
+struct smap_psock {
+	struct rcu_head	rcu;
+
+	/* datapath variables */
+	struct sk_buff_head rxqueue;
+	bool strp_enabled;
+
+	/* datapath error path cache across tx work invocations */
+	int save_rem;
+	int save_off;
+	struct sk_buff *save_skb;
+
+	struct strparser strp;
+	struct bpf_prog *bpf_parse;
+	struct bpf_prog *bpf_verdict;
+	struct bpf_stab *stab;
+
+	/* Back reference used when sock callback trigger sockmap operations */
+	int key;
+	struct sock *sock;
+	unsigned long state;
+
+	struct work_struct tx_work;
+	struct work_struct gc_work;
+
+	void (*save_data_ready)(struct sock *sk);
+	void (*save_write_space)(struct sock *sk);
+	void (*save_state_change)(struct sock *sk);
+};
+
+static inline struct smap_psock *smap_psock_sk(const struct sock *sk)
+{
+	return (struct smap_psock *)rcu_dereference_sk_user_data(sk);
+}
+
+static int smap_verdict_func(struct smap_psock *psock, struct sk_buff *skb)
+{
+	struct bpf_prog *prog = READ_ONCE(psock->bpf_verdict);
+	int rc;
+
+	if (unlikely(!prog))
+		return SK_DROP;
+
+	skb_orphan(skb);
+	skb->sk = psock->sock;
+	bpf_compute_data_end(skb);
+	rc = (*prog->bpf_func)(skb, prog->insnsi);
+	skb->sk = NULL;
+
+	return rc;
+}
+
+static void smap_do_verdict(struct smap_psock *psock, struct sk_buff *skb)
+{
+	struct sock *sock;
+	int rc;
+
+	/* Because we use per cpu values to feed input from sock redirect
+	 * in BPF program to do_sk_redirect_map() call we need to ensure we
+	 * are not preempted. RCU read lock is not sufficient in this case
+	 * with CONFIG_PREEMPT_RCU enabled so we must be explicit here.
+	 */
+	preempt_disable();
+	rc = smap_verdict_func(psock, skb);
+	switch (rc) {
+	case SK_REDIRECT:
+		sock = do_sk_redirect_map();
+		preempt_enable();
+		if (likely(sock)) {
+			struct smap_psock *peer = smap_psock_sk(sock);
+
+			if (likely(peer &&
+				   test_bit(SMAP_TX_RUNNING, &peer->state) &&
+				   sk_stream_memory_free(peer->sock))) {
+				peer->sock->sk_wmem_queued += skb->truesize;
+				sk_mem_charge(peer->sock, skb->truesize);
+				skb_queue_tail(&peer->rxqueue, skb);
+				schedule_work(&peer->tx_work);
+				break;
+			}
+		}
+	/* Fall through and free skb otherwise */
+	case SK_DROP:
+	default:
+		preempt_enable();
+		kfree_skb(skb);
+	}
+}
+
+static void smap_report_sk_error(struct smap_psock *psock, int err)
+{
+	struct sock *sk = psock->sock;
+
+	sk->sk_err = err;
+	sk->sk_error_report(sk);
+}
+
+static void smap_release_sock(struct sock *sock);
+
+/* Called with lock_sock(sk) held */
+static void smap_state_change(struct sock *sk)
+{
+	struct smap_psock *psock;
+	struct sock *osk;
+
+	rcu_read_lock();
+
+	/* Allowing transitions into an established syn_recv states allows
+	 * for early binding sockets to a smap object before the connection
+	 * is established.
+	 */
+	switch (sk->sk_state) {
+	case TCP_SYN_RECV:
+	case TCP_ESTABLISHED:
+		break;
+	case TCP_CLOSE_WAIT:
+	case TCP_CLOSING:
+	case TCP_LAST_ACK:
+	case TCP_FIN_WAIT1:
+	case TCP_FIN_WAIT2:
+	case TCP_LISTEN:
+		break;
+	case TCP_CLOSE:
+		/* Only release if the map entry is in fact the sock in
+		 * question. There is a case where the operator deletes
+		 * the sock from the map, but the TCP sock is closed before
+		 * the psock is detached. Use cmpxchg to verify correct
+		 * sock is removed.
+		 */
+		psock = smap_psock_sk(sk);
+		if (unlikely(!psock))
+			break;
+		osk = cmpxchg(&psock->stab->sock_map[psock->key], sk, NULL);
+		if (osk == sk)
+			smap_release_sock(sk);
+		break;
+	default:
+		smap_report_sk_error(psock, EPIPE);
+		break;
+	}
+	rcu_read_unlock();
+}
+
+static void smap_read_sock_strparser(struct strparser *strp,
+				     struct sk_buff *skb)
+{
+	struct smap_psock *psock;
+
+	rcu_read_lock();
+	psock = container_of(strp, struct smap_psock, strp);
+	smap_do_verdict(psock, skb);
+	rcu_read_unlock();
+}
+
+/* Called with lock held on socket */
+static void smap_data_ready(struct sock *sk)
+{
+	struct smap_psock *psock;
+
+	write_lock_bh(&sk->sk_callback_lock);
+	psock = smap_psock_sk(sk);
+	if (likely(psock))
+		strp_data_ready(&psock->strp);
+	write_unlock_bh(&sk->sk_callback_lock);
+}
+
+static void smap_tx_work(struct work_struct *w)
+{
+	struct smap_psock *psock;
+	struct sk_buff *skb;
+	int rem, off, n;
+
+	psock = container_of(w, struct smap_psock, tx_work);
+
+	/* lock sock to avoid losing sk_socket at some point during loop */
+	lock_sock(psock->sock);
+	if (psock->save_skb) {
+		skb = psock->save_skb;
+		rem = psock->save_rem;
+		off = psock->save_off;
+		psock->save_skb = NULL;
+		goto start;
+	}
+
+	while ((skb = skb_dequeue(&psock->rxqueue))) {
+		rem = skb->len;
+		off = 0;
+start:
+		do {
+			if (likely(psock->sock->sk_socket))
+				n = skb_send_sock_locked(psock->sock,
+							 skb, off, rem);
+			else
+				n = -EINVAL;
+			if (n <= 0) {
+				if (n == -EAGAIN) {
+					/* Retry when space is available */
+					psock->save_skb = skb;
+					psock->save_rem = rem;
+					psock->save_off = off;
+					goto out;
+				}
+				/* Hard errors break pipe and stop xmit */
+				smap_report_sk_error(psock, n ? -n : EPIPE);
+				clear_bit(SMAP_TX_RUNNING, &psock->state);
+				sk_mem_uncharge(psock->sock, skb->truesize);
+				psock->sock->sk_wmem_queued -= skb->truesize;
+				kfree_skb(skb);
+				goto out;
+			}
+			rem -= n;
+			off += n;
+		} while (rem);
+		sk_mem_uncharge(psock->sock, skb->truesize);
+		psock->sock->sk_wmem_queued -= skb->truesize;
+		kfree_skb(skb);
+	}
+out:
+	release_sock(psock->sock);
+}
+
+static void smap_write_space(struct sock *sk)
+{
+	struct smap_psock *psock;
+
+	rcu_read_lock();
+	psock = smap_psock_sk(sk);
+	if (likely(psock && test_bit(SMAP_TX_RUNNING, &psock->state)))
+		schedule_work(&psock->tx_work);
+	rcu_read_unlock();
+}
+
+static void smap_stop_sock(struct smap_psock *psock, struct sock *sk)
+{
+	write_lock_bh(&sk->sk_callback_lock);
+	if (!psock->strp_enabled)
+		goto out;
+	sk->sk_data_ready = psock->save_data_ready;
+	sk->sk_write_space = psock->save_write_space;
+	sk->sk_state_change = psock->save_state_change;
+	psock->save_data_ready = NULL;
+	psock->save_write_space = NULL;
+	psock->save_state_change = NULL;
+	strp_stop(&psock->strp);
+	psock->strp_enabled = false;
+out:
+	write_unlock_bh(&sk->sk_callback_lock);
+}
+
+static void smap_destroy_psock(struct rcu_head *rcu)
+{
+	struct smap_psock *psock = container_of(rcu,
+						  struct smap_psock, rcu);
+
+	/* Now that a grace period has passed there is no longer
+	 * any reference to this sock in the sockmap so we can
+	 * destroy the psock, strparser, and bpf programs. But,
+	 * because we use workqueue sync operations we can not
+	 * do it in rcu context
+	 */
+	schedule_work(&psock->gc_work);
+}
+
+static void smap_release_sock(struct sock *sock)
+{
+	struct smap_psock *psock = smap_psock_sk(sock);
+
+	smap_stop_sock(psock, sock);
+	clear_bit(SMAP_TX_RUNNING, &psock->state);
+	rcu_assign_sk_user_data(sock, NULL);
+	call_rcu_sched(&psock->rcu, smap_destroy_psock);
+}
+
+static int smap_parse_func_strparser(struct strparser *strp,
+				       struct sk_buff *skb)
+{
+	struct smap_psock *psock;
+	struct bpf_prog *prog;
+	int rc;
+
+	rcu_read_lock();
+	psock = container_of(strp, struct smap_psock, strp);
+	prog = READ_ONCE(psock->bpf_parse);
+
+	if (unlikely(!prog)) {
+		rcu_read_unlock();
+		return skb->len;
+	}
+
+	/* Attach socket for bpf program to use if needed we can do this
+	 * because strparser clones the skb before handing it to a upper
+	 * layer, meaning skb_orphan has been called. We NULL sk on the
+	 * way out to ensure we don't trigger a BUG_ON in skb/sk operations
+	 * later and because we are not charging the memory of this skb to
+	 * any socket yet.
+	 */
+	skb->sk = psock->sock;
+	bpf_compute_data_end(skb);
+	rc = (*prog->bpf_func)(skb, prog->insnsi);
+	skb->sk = NULL;
+	rcu_read_unlock();
+	return rc;
+}
+
+
+static int smap_read_sock_done(struct strparser *strp, int err)
+{
+	return err;
+}
+
+static int smap_init_sock(struct smap_psock *psock,
+			  struct sock *sk)
+{
+	struct strp_callbacks cb;
+
+	memset(&cb, 0, sizeof(cb));
+	cb.rcv_msg = smap_read_sock_strparser;
+	cb.parse_msg = smap_parse_func_strparser;
+	cb.read_sock_done = smap_read_sock_done;
+	return strp_init(&psock->strp, sk, &cb);
+}
+
+static void smap_init_progs(struct smap_psock *psock,
+			    struct bpf_stab *stab,
+			    struct bpf_prog *verdict,
+			    struct bpf_prog *parse)
+{
+	struct bpf_prog *orig_parse, *orig_verdict;
+
+	orig_parse = xchg(&psock->bpf_parse, parse);
+	orig_verdict = xchg(&psock->bpf_verdict, verdict);
+
+	if (orig_verdict)
+		bpf_prog_put(orig_verdict);
+	if (orig_parse)
+		bpf_prog_put(orig_parse);
+}
+
+static void smap_start_sock(struct smap_psock *psock, struct sock *sk)
+{
+	if (sk->sk_data_ready == smap_data_ready)
+		return;
+	psock->save_data_ready = sk->sk_data_ready;
+	psock->save_write_space = sk->sk_write_space;
+	psock->save_state_change = sk->sk_state_change;
+	sk->sk_data_ready = smap_data_ready;
+	sk->sk_write_space = smap_write_space;
+	sk->sk_state_change = smap_state_change;
+	psock->strp_enabled = true;
+}
+
+static void sock_map_remove_complete(struct bpf_stab *stab)
+{
+	bpf_map_area_free(stab->sock_map);
+	kfree(stab);
+}
+
+static void smap_gc_work(struct work_struct *w)
+{
+	struct smap_psock *psock;
+
+	psock = container_of(w, struct smap_psock, gc_work);
+
+	/* no callback lock needed because we already detached sockmap ops */
+	if (psock->strp_enabled)
+		strp_done(&psock->strp);
+
+	cancel_work_sync(&psock->tx_work);
+	__skb_queue_purge(&psock->rxqueue);
+
+	/* At this point all strparser and xmit work must be complete */
+	if (psock->bpf_parse)
+		bpf_prog_put(psock->bpf_parse);
+	if (psock->bpf_verdict)
+		bpf_prog_put(psock->bpf_verdict);
+
+	if (refcount_dec_and_test(&psock->stab->refcnt))
+		sock_map_remove_complete(psock->stab);
+
+	sock_put(psock->sock);
+	kfree(psock);
+}
+
+static struct smap_psock *smap_init_psock(struct sock *sock,
+					  struct bpf_stab *stab)
+{
+	struct smap_psock *psock;
+
+	psock = kzalloc(sizeof(struct smap_psock), GFP_ATOMIC | __GFP_NOWARN);
+	if (!psock)
+		return ERR_PTR(-ENOMEM);
+
+	psock->sock = sock;
+	skb_queue_head_init(&psock->rxqueue);
+	INIT_WORK(&psock->tx_work, smap_tx_work);
+	INIT_WORK(&psock->gc_work, smap_gc_work);
+
+	rcu_assign_sk_user_data(sock, psock);
+	sock_hold(sock);
+	return psock;
+}
+
+static struct bpf_map *sock_map_alloc(union bpf_attr *attr)
+{
+	struct bpf_stab *stab;
+	int err = -EINVAL;
+	u64 cost;
+
+	/* check sanity of attributes */
+	if (attr->max_entries == 0 || attr->key_size != 4 ||
+	    attr->value_size != 4 || attr->map_flags)
+		return ERR_PTR(-EINVAL);
+
+	if (attr->value_size > KMALLOC_MAX_SIZE)
+		return ERR_PTR(-E2BIG);
+
+	stab = kzalloc(sizeof(*stab), GFP_USER);
+	if (!stab)
+		return ERR_PTR(-ENOMEM);
+
+	/* mandatory map attributes */
+	stab->map.map_type = attr->map_type;
+	stab->map.key_size = attr->key_size;
+	stab->map.value_size = attr->value_size;
+	stab->map.max_entries = attr->max_entries;
+	stab->map.map_flags = attr->map_flags;
+
+	/* make sure page count doesn't overflow */
+	cost = (u64) stab->map.max_entries * sizeof(struct sock *);
+	if (cost >= U32_MAX - PAGE_SIZE)
+		goto free_stab;
+
+	stab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
+
+	/* if map size is larger than memlock limit, reject it early */
+	err = bpf_map_precharge_memlock(stab->map.pages);
+	if (err)
+		goto free_stab;
+
+	stab->sock_map = bpf_map_area_alloc(stab->map.max_entries *
+					    sizeof(struct sock *));
+	if (!stab->sock_map)
+		goto free_stab;
+
+	refcount_set(&stab->refcnt, 1);
+	return &stab->map;
+free_stab:
+	kfree(stab);
+	return ERR_PTR(err);
+}
+
+static void sock_map_free(struct bpf_map *map)
+{
+	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+	int i;
+
+	synchronize_rcu();
+
+	/* At this point no update, lookup or delete operations can happen.
+	 * However, be aware we can still get a socket state event updates,
+	 * and data ready callabacks that reference the psock from sk_user_data
+	 * Also psock worker threads are still in-flight. So smap_release_sock
+	 * will only free the psock after cancel_sync on the worker threads
+	 * and a grace period expire to ensure psock is really safe to remove.
+	 */
+	rcu_read_lock();
+	for (i = 0; i < stab->map.max_entries; i++) {
+		struct sock *sock;
+
+		sock = xchg(&stab->sock_map[i], NULL);
+		if (!sock)
+			continue;
+
+		smap_release_sock(sock);
+	}
+	rcu_read_unlock();
+
+	if (stab->bpf_verdict)
+		bpf_prog_put(stab->bpf_verdict);
+	if (stab->bpf_parse)
+		bpf_prog_put(stab->bpf_parse);
+
+	if (refcount_dec_and_test(&stab->refcnt))
+		sock_map_remove_complete(stab);
+}
+
+static int sock_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
+{
+	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+	u32 i = key ? *(u32 *)key : U32_MAX;
+	u32 *next = (u32 *)next_key;
+
+	if (i >= stab->map.max_entries) {
+		*next = 0;
+		return 0;
+	}
+
+	if (i == stab->map.max_entries - 1)
+		return -ENOENT;
+
+	*next = i + 1;
+	return 0;
+}
+
+struct sock  *__sock_map_lookup_elem(struct bpf_map *map, u32 key)
+{
+	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+
+	if (key >= map->max_entries)
+		return NULL;
+
+	return READ_ONCE(stab->sock_map[key]);
+}
+
+static int sock_map_delete_elem(struct bpf_map *map, void *key)
+{
+	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+	int k = *(u32 *)key;
+	struct sock *sock;
+
+	if (k >= map->max_entries)
+		return -EINVAL;
+
+	sock = xchg(&stab->sock_map[k], NULL);
+	if (!sock)
+		return -EINVAL;
+
+	smap_release_sock(sock);
+	return 0;
+}
+
+/* Locking notes: Concurrent updates, deletes, and lookups are allowed and are
+ * done inside rcu critical sections. This ensures on updates that the psock
+ * will not be released via smap_release_sock() until concurrent updates/deletes
+ * complete. All operations operate on sock_map using cmpxchg and xchg
+ * operations to ensure we do not get stale references. Any reads into the
+ * map must be done with READ_ONCE() because of this.
+ *
+ * A psock is destroyed via call_rcu and after any worker threads are cancelled
+ * and syncd so we are certain all references from the update/lookup/delete
+ * operations as well as references in the data path are no longer in use.
+ *
+ * A psock object holds a refcnt on the sockmap it is attached to and this is
+ * not decremented until after a RCU grace period and garbage collection occurs.
+ * This ensures the map is not free'd until psocks linked to it are removed. The
+ * map link is used when the independent sock events trigger map deletion.
+ *
+ * Psocks may only participate in one sockmap at a time. Users that try to
+ * join a single sock to multiple maps will get an error.
+ *
+ * Last, but not least, it is possible the socket is closed while running
+ * an update on an existing psock. This will release the psock, but again
+ * not until the update has completed due to rcu grace period rules.
+ */
+static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops,
+				    struct bpf_map *map,
+				    void *key, u64 flags, u64 map_flags)
+{
+	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+	struct bpf_prog *verdict, *parse;
+	struct smap_psock *psock = NULL;
+	struct sock *old_sock, *sock;
+	u32 i = *(u32 *)key;
+	bool update = false;
+	int err = 0;
+
+	if (unlikely(flags > BPF_EXIST))
+		return -EINVAL;
+
+	if (unlikely(i >= stab->map.max_entries))
+		return -E2BIG;
+
+	if (unlikely(map_flags > BPF_SOCKMAP_STRPARSER))
+		return -EINVAL;
+
+	verdict = parse = NULL;
+	sock = READ_ONCE(stab->sock_map[i]);
+
+	if (flags == BPF_EXIST || flags == BPF_ANY) {
+		if (!sock && flags == BPF_EXIST) {
+			return -ENOENT;
+		} else if (sock && sock != skops->sk) {
+			return -EINVAL;
+		} else if (sock) {
+			psock = smap_psock_sk(sock);
+			if (unlikely(!psock))
+				return -EBUSY;
+			update = true;
+		}
+	} else if (sock && BPF_NOEXIST) {
+		return -EEXIST;
+	}
+
+	/* reserve BPF programs early so can abort easily on failures */
+	if (map_flags & BPF_SOCKMAP_STRPARSER) {
+		verdict = READ_ONCE(stab->bpf_verdict);
+		parse = READ_ONCE(stab->bpf_parse);
+
+		if (!verdict || !parse)
+			return -ENOENT;
+
+		/* bpf prog refcnt may be zero if a concurrent attach operation
+		 * removes the program after the above READ_ONCE() but before
+		 * we increment the refcnt. If this is the case abort with an
+		 * error.
+		 */
+		verdict = bpf_prog_inc_not_zero(stab->bpf_verdict);
+		if (IS_ERR(verdict))
+			return PTR_ERR(verdict);
+
+		parse = bpf_prog_inc_not_zero(stab->bpf_parse);
+		if (IS_ERR(parse)) {
+			bpf_prog_put(verdict);
+			return PTR_ERR(parse);
+		}
+	}
+
+	if (!psock) {
+		sock = skops->sk;
+		if (rcu_dereference_sk_user_data(sock))
+			return -EEXIST;
+		psock = smap_init_psock(sock, stab);
+		if (IS_ERR(psock)) {
+			if (verdict)
+				bpf_prog_put(verdict);
+			if (parse)
+				bpf_prog_put(parse);
+			return PTR_ERR(psock);
+		}
+		psock->key = i;
+		psock->stab = stab;
+		refcount_inc(&stab->refcnt);
+		set_bit(SMAP_TX_RUNNING, &psock->state);
+	}
+
+	if (map_flags & BPF_SOCKMAP_STRPARSER) {
+		write_lock_bh(&sock->sk_callback_lock);
+		if (psock->strp_enabled)
+			goto start_done;
+		err = smap_init_sock(psock, sock);
+		if (err)
+			goto out;
+		smap_init_progs(psock, stab, verdict, parse);
+		smap_start_sock(psock, sock);
+start_done:
+		write_unlock_bh(&sock->sk_callback_lock);
+	} else if (update) {
+		smap_stop_sock(psock, sock);
+	}
+
+	if (!update) {
+		old_sock = xchg(&stab->sock_map[i], skops->sk);
+		if (old_sock)
+			smap_release_sock(old_sock);
+	}
+
+	return 0;
+out:
+	write_unlock_bh(&sock->sk_callback_lock);
+	if (!update)
+		smap_release_sock(sock);
+	return err;
+}
+
+static int sock_map_attach_prog(struct bpf_map *map,
+				struct bpf_prog *parse,
+				struct bpf_prog *verdict)
+{
+	struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+	struct bpf_prog *_parse, *_verdict;
+
+	_parse = xchg(&stab->bpf_parse, parse);
+	_verdict = xchg(&stab->bpf_verdict, verdict);
+
+	if (_parse)
+		bpf_prog_put(_parse);
+	if (_verdict)
+		bpf_prog_put(_verdict);
+
+	return 0;
+}
+
+static void *sock_map_lookup(struct bpf_map *map, void *key)
+{
+	return NULL;
+}
+
+static int sock_map_update_elem(struct bpf_map *map,
+				void *key, void *value, u64 flags)
+{
+	struct bpf_sock_ops_kern skops;
+	u32 fd = *(u32 *)value;
+	struct socket *socket;
+	int err;
+
+	socket = sockfd_lookup(fd, &err);
+	if (!socket)
+		return err;
+
+	skops.sk = socket->sk;
+	if (!skops.sk) {
+		fput(socket->file);
+		return -EINVAL;
+	}
+
+	err = sock_map_ctx_update_elem(&skops, map, key,
+				       flags, BPF_SOCKMAP_STRPARSER);
+	fput(socket->file);
+	return err;
+}
+
+const struct bpf_map_ops sock_map_ops = {
+	.map_alloc = sock_map_alloc,
+	.map_free = sock_map_free,
+	.map_lookup_elem = sock_map_lookup,
+	.map_get_next_key = sock_map_get_next_key,
+	.map_update_elem = sock_map_update_elem,
+	.map_delete_elem = sock_map_delete_elem,
+	.map_attach = sock_map_attach_prog,
+};
+
+BPF_CALL_5(bpf_sock_map_update, struct bpf_sock_ops_kern *, bpf_sock,
+	   struct bpf_map *, map, void *, key, u64, flags, u64, map_flags)
+{
+	WARN_ON_ONCE(!rcu_read_lock_held());
+	return sock_map_ctx_update_elem(bpf_sock, map, key, flags, map_flags);
+}
+
+const struct bpf_func_proto bpf_sock_map_update_proto = {
+	.func		= bpf_sock_map_update,
+	.gpl_only	= false,
+	.pkt_access	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_CONST_MAP_PTR,
+	.arg3_type	= ARG_PTR_TO_MAP_KEY,
+	.arg4_type	= ARG_ANYTHING,
+	.arg5_type	= ARG_ANYTHING,
+};

kernel/bpf/syscall.c

@@ -1087,7 +1087,50 @@ static int bpf_obj_get(const union bpf_attr *attr)
 
 #ifdef CONFIG_CGROUP_BPF
 
-#define BPF_PROG_ATTACH_LAST_FIELD attach_flags
+#define BPF_PROG_ATTACH_LAST_FIELD attach_bpf_fd2
+
+static int sockmap_get_from_fd(const union bpf_attr *attr, int ptype)
+{
+	struct bpf_prog *prog1, *prog2;
+	int ufd = attr->target_fd;
+	struct bpf_map *map;
+	struct fd f;
+	int err;
+
+	f = fdget(ufd);
+	map = __bpf_map_get(f);
+	if (IS_ERR(map))
+		return PTR_ERR(map);
+
+	if (!map->ops->map_attach) {
+		fdput(f);
+		return -EOPNOTSUPP;
+	}
+
+	prog1 = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
+	if (IS_ERR(prog1)) {
+		fdput(f);
+		return PTR_ERR(prog1);
+	}
+
+	prog2 = bpf_prog_get_type(attr->attach_bpf_fd2, ptype);
+	if (IS_ERR(prog2)) {
+		fdput(f);
+		bpf_prog_put(prog1);
+		return PTR_ERR(prog2);
+	}
+
+	err = map->ops->map_attach(map, prog1, prog2);
+	if (err) {
+		fdput(f);
+		bpf_prog_put(prog1);
+		bpf_prog_put(prog2);
+		return PTR_ERR(map);
+	}
+
+	fdput(f);
+	return err;
+}
 
 static int bpf_prog_attach(const union bpf_attr *attr)
 {
@@ -1116,10 +1159,16 @@ static int bpf_prog_attach(const union bpf_attr *attr)
 	case BPF_CGROUP_SOCK_OPS:
 		ptype = BPF_PROG_TYPE_SOCK_OPS;
 		break;
+	case BPF_CGROUP_SMAP_INGRESS:
+		ptype = BPF_PROG_TYPE_SK_SKB;
+		break;
 	default:
 		return -EINVAL;
 	}
 
+	if (attr->attach_type == BPF_CGROUP_SMAP_INGRESS)
+		return sockmap_get_from_fd(attr, ptype);
+
 	prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
 	if (IS_ERR(prog))
 		return PTR_ERR(prog);

kernel/bpf/verifier.c

@@ -1522,6 +1522,12 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
 	case BPF_MAP_TYPE_HASH_OF_MAPS:
 		if (func_id != BPF_FUNC_map_lookup_elem)
 			goto error;
+	case BPF_MAP_TYPE_SOCKMAP:
+		if (func_id != BPF_FUNC_sk_redirect_map &&
+		    func_id != BPF_FUNC_sock_map_update &&
+		    func_id != BPF_FUNC_map_delete_elem)
+			goto error;
+		break;
 	default:
 		break;
 	}
@@ -1550,6 +1556,14 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
 		if (map->map_type != BPF_MAP_TYPE_DEVMAP)
 			goto error;
 		break;
+	case BPF_FUNC_sk_redirect_map:
+		if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
+			goto error;
+		break;
+	case BPF_FUNC_sock_map_update:
+		if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
+			goto error;
+		break;
 	default:
 		break;
 	}

net/core/filter.c

@@ -1858,6 +1858,45 @@ static const struct bpf_func_proto bpf_redirect_map_proto = {
 	.arg3_type      = ARG_ANYTHING,
 };
 
+BPF_CALL_3(bpf_sk_redirect_map, struct bpf_map *, map, u32, key, u64, flags)
+{
+	struct redirect_info *ri = this_cpu_ptr(&redirect_info);
+
+	if (unlikely(flags))
+		return SK_ABORTED;
+
+	ri->ifindex = key;
+	ri->flags = flags;
+	ri->map = map;
+
+	return SK_REDIRECT;
+}
+
+struct sock *do_sk_redirect_map(void)
+{
+	struct redirect_info *ri = this_cpu_ptr(&redirect_info);
+	struct sock *sk = NULL;
+
+	if (ri->map) {
+		sk = __sock_map_lookup_elem(ri->map, ri->ifindex);
+
+		ri->ifindex = 0;
+		ri->map = NULL;
+		/* we do not clear flags for future lookup */
+	}
+
+	return sk;
+}
+
+static const struct bpf_func_proto bpf_sk_redirect_map_proto = {
+	.func           = bpf_sk_redirect_map,
+	.gpl_only       = false,
+	.ret_type       = RET_INTEGER,
+	.arg1_type      = ARG_CONST_MAP_PTR,
+	.arg2_type      = ARG_ANYTHING,
+	.arg3_type      = ARG_ANYTHING,
+};
+
 BPF_CALL_1(bpf_get_cgroup_classid, const struct sk_buff *, skb)
 {
 	return task_get_classid(skb);
@@ -3229,6 +3268,8 @@ static const struct bpf_func_proto *
 	switch (func_id) {
 	case BPF_FUNC_setsockopt:
 		return &bpf_setsockopt_proto;
+	case BPF_FUNC_sock_map_update:
+		return &bpf_sock_map_update_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}
@@ -3243,6 +3284,8 @@ static const struct bpf_func_proto *sk_skb_func_proto(enum bpf_func_id func_id)
 		return &bpf_get_socket_cookie_proto;
 	case BPF_FUNC_get_socket_uid:
 		return &bpf_get_socket_uid_proto;
+	case BPF_FUNC_sk_redirect_map:
+		return &bpf_sk_redirect_map_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}