This patch introduces a new bpf_attach_type for BPF_PROG_TYPE_SK_REUSEPORT
to check if the attached eBPF program is capable of migrating sockets. When
the eBPF program is attached, we run it for socket migration if the
expected_attach_type is BPF_SK_REUSEPORT_SELECT_OR_MIGRATE or
net.ipv4.tcp_migrate_req is enabled.
Currently, the expected_attach_type is not enforced for the
BPF_PROG_TYPE_SK_REUSEPORT type of program. Thus, this commit follows the
earlier idea in the commit aac3fc320d94 ("bpf: Post-hooks for sys_bind") to
fix up the zero expected_attach_type in bpf_prog_load_fixup_attach_type().
Moreover, this patch adds a new field (migrating_sk) to sk_reuseport_md to
select a new listener based on the child socket. migrating_sk varies
depending on if it is migrating a request in the accept queue or during
3WHS.
- accept_queue : sock (ESTABLISHED/SYN_RECV)
- 3WHS : request_sock (NEW_SYN_RECV)
In the eBPF program, we can select a new listener by
BPF_FUNC_sk_select_reuseport(). Also, we can cancel migration by returning
SK_DROP. This feature is useful when listeners have different settings at
the socket API level or when we want to free resources as soon as possible.
- SK_PASS with selected_sk, select it as a new listener
- SK_PASS with selected_sk NULL, fallbacks to the random selection
- SK_DROP, cancel the migration.
There is a noteworthy point. We select a listening socket in three places,
but we do not have struct skb at closing a listener or retransmitting a
SYN+ACK. On the other hand, some helper functions do not expect skb is NULL
(e.g. skb_header_pointer() in BPF_FUNC_skb_load_bytes(), skb_tail_pointer()
in BPF_FUNC_skb_load_bytes_relative()). So we allocate an empty skb
temporarily before running the eBPF program.
Link: https://lore.kernel.org/netdev/20201123003828.xjpjdtk4ygl6tg6h@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Link: https://lore.kernel.org/netdev/20201203042402.6cskdlit5f3mw4ru@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Link: https://lore.kernel.org/netdev/20201209030903.hhow5r53l6fmozjn@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Suggested-by: Martin KaFai Lau <kafai@xxxxxx>
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx>
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
---
include/linux/bpf.h | 1 +
include/linux/filter.h | 2 ++
include/uapi/linux/bpf.h | 15 +++++++++++++++
kernel/bpf/syscall.c | 13 +++++++++++++
net/core/filter.c | 13 ++++++++++++-
net/core/sock_reuseport.c | 34 ++++++++++++++++++++++++++++++----
tools/include/uapi/linux/bpf.h | 15 +++++++++++++++
7 files changed, 88 insertions(+), 5 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9dc44ba97584..5aa62785c078 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2026,6 +2026,7 @@ struct sk_reuseport_kern {
struct sk_buff *skb;
struct sock *sk;
struct sock *selected_sk;
+ struct sock *migrating_sk;
void *data_end;
u32 hash;
u32 reuseport_id;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 9a09547bc7ba..226f76c0b974 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -995,11 +995,13 @@ void bpf_warn_invalid_xdp_action(u32 act);
#ifdef CONFIG_INET
struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
struct bpf_prog *prog, struct sk_buff *skb,
+ struct sock *migrating_sk,
u32 hash);
#else
static inline struct sock *
bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
struct bpf_prog *prog, struct sk_buff *skb,
+ struct sock *migrating_sk,
u32 hash)
{
return NULL;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2488a62482bb..f2972836fecd 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -981,6 +981,8 @@ enum bpf_attach_type {
BPF_SK_LOOKUP,
BPF_XDP,
BPF_SK_SKB_VERDICT,
+ BPF_SK_REUSEPORT_SELECT,
+ BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
__MAX_BPF_ATTACH_TYPE
};
@@ -5393,7 +5395,20 @@ struct sk_reuseport_md {
__u32 ip_protocol; /* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
__u32 bind_inany; /* Is sock bound to an INANY address? */
__u32 hash; /* A hash of the packet 4 tuples */
+ /* When reuse->migrating_sk is NULL, it is selecting a sk for the
+ * new incoming connection request (e.g. selecting a listen sk for
+ * the received SYN in the TCP case). reuse->sk is one of the sk
+ * in the reuseport group. The bpf prog can use reuse->sk to learn
+ * the local listening ip/port without looking into the skb.
+ *
+ * When reuse->migrating_sk is not NULL, reuse->sk is closed and
+ * reuse->migrating_sk is the socket that needs to be migrated
+ * to another listening socket. migrating_sk could be a fullsock
+ * sk that is fully established or a reqsk that is in-the-middle
+ * of 3-way handshake.
+ */
__bpf_md_ptr(struct bpf_sock *, sk);
+ __bpf_md_ptr(struct bpf_sock *, migrating_sk);
};
#define BPF_TAG_SIZE 8
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 1d1cd80a6e67..caf41567e4d1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1946,6 +1946,11 @@ static void bpf_prog_load_fixup_attach_type(union bpf_attr *attr)
attr->expected_attach_type =
BPF_CGROUP_INET_SOCK_CREATE;
break;
+ case BPF_PROG_TYPE_SK_REUSEPORT:
+ if (!attr->expected_attach_type)
+ attr->expected_attach_type =
+ BPF_SK_REUSEPORT_SELECT;
+ break;
}
}
@@ -2029,6 +2034,14 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
if (expected_attach_type == BPF_SK_LOOKUP)
return 0;
return -EINVAL;
+ case BPF_PROG_TYPE_SK_REUSEPORT:
+ switch (expected_attach_type) {
+ case BPF_SK_REUSEPORT_SELECT:
+ case BPF_SK_REUSEPORT_SELECT_OR_MIGRATE:
+ return 0;
+ default:
+ return -EINVAL;
+ }
case BPF_PROG_TYPE_SYSCALL:
case BPF_PROG_TYPE_EXT:
if (expected_attach_type)
diff --git a/net/core/filter.c b/net/core/filter.c
index b7818c707f60..89b5c5eefd5f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -10011,11 +10011,13 @@ int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
static void bpf_init_reuseport_kern(struct sk_reuseport_kern *reuse_kern,
struct sock_reuseport *reuse,
struct sock *sk, struct sk_buff *skb,
+ struct sock *migrating_sk,
u32 hash)
{
reuse_kern->skb = skb;
reuse_kern->sk = sk;
reuse_kern->selected_sk = NULL;
+ reuse_kern->migrating_sk = migrating_sk;
reuse_kern->data_end = skb->data + skb_headlen(skb);
reuse_kern->hash = hash;
reuse_kern->reuseport_id = reuse->reuseport_id;
@@ -10024,12 +10026,13 @@ static void bpf_init_reuseport_kern(struct sk_reuseport_kern *reuse_kern,
struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
struct bpf_prog *prog, struct sk_buff *skb,
+ struct sock *migrating_sk,
u32 hash)
{
struct sk_reuseport_kern reuse_kern;
enum sk_action action;
- bpf_init_reuseport_kern(&reuse_kern, reuse, sk, skb, hash);
+ bpf_init_reuseport_kern(&reuse_kern, reuse, sk, skb, migrating_sk, hash);
action = BPF_PROG_RUN(prog, &reuse_kern);
if (action == SK_PASS)
@@ -10174,6 +10177,10 @@ sk_reuseport_is_valid_access(int off, int size,
info->reg_type = PTR_TO_SOCKET;
return size == sizeof(__u64);
+ case offsetof(struct sk_reuseport_md, migrating_sk):
+ info->reg_type = PTR_TO_SOCK_COMMON_OR_NULL;
+ return size == sizeof(__u64);
+
/* Fields that allow narrowing */
case bpf_ctx_range(struct sk_reuseport_md, eth_protocol):
if (size < sizeof_field(struct sk_buff, protocol))
@@ -10250,6 +10257,10 @@ static u32 sk_reuseport_convert_ctx_access(enum bpf_access_type type,
case offsetof(struct sk_reuseport_md, sk):
SK_REUSEPORT_LOAD_FIELD(sk);
break;
+
+ case offsetof(struct sk_reuseport_md, migrating_sk):
+ SK_REUSEPORT_LOAD_FIELD(migrating_sk);
+ break;
}
return insn - insn_buf;
diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
index 193a3281ddda..8773368eaa78 100644
--- a/net/core/sock_reuseport.c
+++ b/net/core/sock_reuseport.c
@@ -378,13 +378,17 @@ void reuseport_stop_listen_sock(struct sock *sk)
{
if (sk->sk_protocol == IPPROTO_TCP) {
struct sock_reuseport *reuse;
+ struct bpf_prog *prog;
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
+ prog = rcu_dereference_protected(reuse->prog,
+ lockdep_is_held(&reuseport_lock));
- if (sock_net(sk)->ipv4.sysctl_tcp_migrate_req) {
+ if (sock_net(sk)->ipv4.sysctl_tcp_migrate_req ||
+ (prog && prog->expected_attach_type == BPF_SK_REUSEPORT_SELECT_OR_MIGRATE)) {
/* Migration capable, move sk from the listening section
* to the closed section.
*/
@@ -489,7 +493,7 @@ struct sock *reuseport_select_sock(struct sock *sk,
goto select_by_hash;
if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT)
- sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, hash);
+ sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, NULL, hash);
else
sk2 = run_bpf_filter(reuse, socks, prog, skb, hdr_len);
@@ -520,6 +524,8 @@ struct sock *reuseport_migrate_sock(struct sock *sk,
{
struct sock_reuseport *reuse;
struct sock *nsk = NULL;
+ bool allocated = false;
+ struct bpf_prog *prog;
u16 socks;
u32 hash;
@@ -537,10 +543,30 @@ struct sock *reuseport_migrate_sock(struct sock *sk,
smp_rmb();
hash = migrating_sk->sk_hash;
- if (sock_net(sk)->ipv4.sysctl_tcp_migrate_req)
+ prog = rcu_dereference(reuse->prog);
+ if (!prog || prog->expected_attach_type != BPF_SK_REUSEPORT_SELECT_OR_MIGRATE) {
+ if (sock_net(sk)->ipv4.sysctl_tcp_migrate_req)
+ goto select_by_hash;
+ goto out;
+ }
+
+ if (!skb) {
+ skb = alloc_skb(0, GFP_ATOMIC);
+ if (!skb)
+ goto out;
+ allocated = true;
+ }
+
+ nsk = bpf_run_sk_reuseport(reuse, sk, prog, skb, migrating_sk, hash);
+
+ if (allocated)
+ kfree_skb(skb);
+
+select_by_hash:
+ if (!nsk)
nsk = reuseport_select_sock_by_hash(reuse, hash, socks);
- if (nsk && unlikely(!refcount_inc_not_zero(&nsk->sk_refcnt)))
+ if (IS_ERR_OR_NULL(nsk) || unlikely(!refcount_inc_not_zero(&nsk->sk_refcnt)))
nsk = NULL;
out:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 2488a62482bb..f2972836fecd 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -981,6 +981,8 @@ enum bpf_attach_type {
BPF_SK_LOOKUP,
BPF_XDP,
BPF_SK_SKB_VERDICT,
+ BPF_SK_REUSEPORT_SELECT,
+ BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
__MAX_BPF_ATTACH_TYPE
};
@@ -5393,7 +5395,20 @@ struct sk_reuseport_md {
__u32 ip_protocol; /* IP protocol. e.g. IPPROTO_TCP, IPPROTO_UDP */
__u32 bind_inany; /* Is sock bound to an INANY address? */
__u32 hash; /* A hash of the packet 4 tuples */
+ /* When reuse->migrating_sk is NULL, it is selecting a sk for the
+ * new incoming connection request (e.g. selecting a listen sk for
+ * the received SYN in the TCP case). reuse->sk is one of the sk
+ * in the reuseport group. The bpf prog can use reuse->sk to learn
+ * the local listening ip/port without looking into the skb.
+ *
+ * When reuse->migrating_sk is not NULL, reuse->sk is closed and
+ * reuse->migrating_sk is the socket that needs to be migrated
+ * to another listening socket. migrating_sk could be a fullsock
+ * sk that is fully established or a reqsk that is in-the-middle
+ * of 3-way handshake.
+ */
__bpf_md_ptr(struct bpf_sock *, sk);
+ __bpf_md_ptr(struct bpf_sock *, migrating_sk);
};
#define BPF_TAG_SIZE 8
--
2.30.2
