Commit 2dbb9b9e authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Daniel Borkmann

bpf: Introduce BPF_PROG_TYPE_SK_REUSEPORT

This patch adds a BPF_PROG_TYPE_SK_REUSEPORT which can select
a SO_REUSEPORT sk from a BPF_MAP_TYPE_REUSEPORT_ARRAY.  Like other
non SK_FILTER/CGROUP_SKB program, it requires CAP_SYS_ADMIN.

BPF_PROG_TYPE_SK_REUSEPORT introduces "struct sk_reuseport_kern"
to store the bpf context instead of using the skb->cb[48].

At the SO_REUSEPORT sk lookup time, it is in the middle of transiting
from a lower layer (ipv4/ipv6) to a upper layer (udp/tcp).  At this
point,  it is not always clear where the bpf context can be appended
in the skb->cb[48] to avoid saving-and-restoring cb[].  Even putting
aside the difference between ipv4-vs-ipv6 and udp-vs-tcp.  It is not
clear if the lower layer is only ipv4 and ipv6 in the future and
will it not touch the cb[] again before transiting to the upper
layer.

For example, in udp_gro_receive(), it uses the 48 byte NAPI_GRO_CB
instead of IP[6]CB and it may still modify the cb[] after calling
the udp[46]_lib_lookup_skb().  Because of the above reason, if
sk->cb is used for the bpf ctx, saving-and-restoring is needed
and likely the whole 48 bytes cb[] has to be saved and restored.

Instead of saving, setting and restoring the cb[], this patch opts
to create a new "struct sk_reuseport_kern" and setting the needed
values in there.

The new BPF_PROG_TYPE_SK_REUSEPORT and "struct sk_reuseport_(kern|md)"
will serve all ipv4/ipv6 + udp/tcp combinations.  There is no protocol
specific usage at this point and it is also inline with the current
sock_reuseport.c implementation (i.e. no protocol specific requirement).

In "struct sk_reuseport_md", this patch exposes data/data_end/len
with semantic similar to other existing usages.  Together
with "bpf_skb_load_bytes()" and "bpf_skb_load_bytes_relative()",
the bpf prog can peek anywhere in the skb.  The "bind_inany" tells
the bpf prog that the reuseport group is bind-ed to a local
INANY address which cannot be learned from skb.

The new "bind_inany" is added to "struct sock_reuseport" which will be
used when running the new "BPF_PROG_TYPE_SK_REUSEPORT" bpf prog in order
to avoid repeating the "bind INANY" test on
"sk_v6_rcv_saddr/sk->sk_rcv_saddr" every time a bpf prog is run.  It can
only be properly initialized when a "sk->sk_reuseport" enabled sk is
adding to a hashtable (i.e. during "reuseport_alloc()" and
"reuseport_add_sock()").

The new "sk_select_reuseport()" is the main helper that the
bpf prog will use to select a SO_REUSEPORT sk.  It is the only function
that can use the new BPF_MAP_TYPE_REUSEPORT_ARRAY.  As mentioned in
the earlier patch, the validity of a selected sk is checked in
run time in "sk_select_reuseport()".  Doing the check in
verification time is difficult and inflexible (consider the map-in-map
use case).  The runtime check is to compare the selected sk's reuseport_id
with the reuseport_id that we want.  This helper will return -EXXX if the
selected sk cannot serve the incoming request (e.g. reuseport_id
not match).  The bpf prog can decide if it wants to do SK_DROP as its
discretion.

When the bpf prog returns SK_PASS, the kernel will check if a
valid sk has been selected (i.e. "reuse_kern->selected_sk != NULL").
If it does , it will use the selected sk.  If not, the kernel
will select one from "reuse->socks[]" (as before this patch).

The SK_DROP and SK_PASS handling logic will be in the next patch.
Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 5dc4c4b7
......@@ -29,6 +29,9 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
#ifdef CONFIG_BPF_LIRC_MODE2
BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2)
#endif
#ifdef CONFIG_INET
BPF_PROG_TYPE(BPF_PROG_TYPE_SK_REUSEPORT, sk_reuseport)
#endif
BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)
......
......@@ -32,6 +32,7 @@ struct seccomp_data;
struct bpf_prog_aux;
struct xdp_rxq_info;
struct xdp_buff;
struct sock_reuseport;
/* ArgX, context and stack frame pointer register positions. Note,
* Arg1, Arg2, Arg3, etc are used as argument mappings of function
......@@ -833,6 +834,20 @@ void bpf_warn_invalid_xdp_action(u32 act);
struct sock *do_sk_redirect_map(struct sk_buff *skb);
struct sock *do_msg_redirect_map(struct sk_msg_buff *md);
#ifdef CONFIG_INET
struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
struct bpf_prog *prog, struct sk_buff *skb,
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,
u32 hash)
{
return NULL;
}
#endif
#ifdef CONFIG_BPF_JIT
extern int bpf_jit_enable;
extern int bpf_jit_harden;
......
......@@ -108,6 +108,7 @@ int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr,
u32 banned_flags);
bool inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
bool match_wildcard);
bool inet_rcv_saddr_any(const struct sock *sk);
void addrconf_join_solict(struct net_device *dev, const struct in6_addr *addr);
void addrconf_leave_solict(struct inet6_dev *idev, const struct in6_addr *addr);
......
......@@ -21,12 +21,14 @@ struct sock_reuseport {
unsigned int synq_overflow_ts;
/* ID stays the same even after the size of socks[] grows. */
unsigned int reuseport_id;
bool bind_inany;
struct bpf_prog __rcu *prog; /* optional BPF sock selector */
struct sock *socks[0]; /* array of sock pointers */
};
extern int reuseport_alloc(struct sock *sk);
extern int reuseport_add_sock(struct sock *sk, struct sock *sk2);
extern int reuseport_alloc(struct sock *sk, bool bind_inany);
extern int reuseport_add_sock(struct sock *sk, struct sock *sk2,
bool bind_inany);
extern void reuseport_detach_sock(struct sock *sk);
extern struct sock *reuseport_select_sock(struct sock *sk,
u32 hash,
......
......@@ -151,6 +151,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
BPF_PROG_TYPE_LWT_SEG6LOCAL,
BPF_PROG_TYPE_LIRC_MODE2,
BPF_PROG_TYPE_SK_REUSEPORT,
};
enum bpf_attach_type {
......@@ -2114,6 +2115,14 @@ union bpf_attr {
* the shared data.
* Return
* Pointer to the local storage area.
*
* int bpf_sk_select_reuseport(struct sk_reuseport_md *reuse, struct bpf_map *map, void *key, u64 flags)
* Description
* Select a SO_REUSEPORT sk from a BPF_MAP_TYPE_REUSEPORT_ARRAY map
* It checks the selected sk is matching the incoming
* request in the skb.
* Return
* 0 on success, or a negative error in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
......@@ -2197,7 +2206,8 @@ union bpf_attr {
FN(rc_keydown), \
FN(skb_cgroup_id), \
FN(get_current_cgroup_id), \
FN(get_local_storage),
FN(get_local_storage), \
FN(sk_select_reuseport),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
......@@ -2414,6 +2424,30 @@ struct sk_msg_md {
__u32 local_port; /* stored in host byte order */
};
struct sk_reuseport_md {
/*
* Start of directly accessible data. It begins from
* the tcp/udp header.
*/
void *data;
void *data_end; /* End of directly accessible data */
/*
* Total length of packet (starting from the tcp/udp header).
* Note that the directly accessible bytes (data_end - data)
* could be less than this "len". Those bytes could be
* indirectly read by a helper "bpf_skb_load_bytes()".
*/
__u32 len;
/*
* Eth protocol in the mac header (network byte order). e.g.
* ETH_P_IP(0x0800) and ETH_P_IPV6(0x86DD)
*/
__u32 eth_protocol;
__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 */
};
#define BPF_TAG_SIZE 8
struct bpf_prog_info {
......
......@@ -1310,6 +1310,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
case BPF_PROG_TYPE_LWT_IN:
case BPF_PROG_TYPE_LWT_OUT:
case BPF_PROG_TYPE_LWT_SEG6LOCAL:
case BPF_PROG_TYPE_SK_REUSEPORT:
/* dst_input() and dst_output() can't write for now */
if (t == BPF_WRITE)
return false;
......@@ -2166,6 +2167,10 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
func_id != BPF_FUNC_msg_redirect_hash)
goto error;
break;
case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
if (func_id != BPF_FUNC_sk_select_reuseport)
goto error;
break;
default:
break;
}
......@@ -2217,6 +2222,10 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
if (map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE)
goto error;
break;
case BPF_FUNC_sk_select_reuseport:
if (map->map_type != BPF_MAP_TYPE_REUSEPORT_SOCKARRAY)
goto error;
break;
default:
break;
}
......
......@@ -1462,7 +1462,7 @@ static int __reuseport_attach_prog(struct bpf_prog *prog, struct sock *sk)
return -ENOMEM;
if (sk_unhashed(sk) && sk->sk_reuseport) {
err = reuseport_alloc(sk);
err = reuseport_alloc(sk, false);
if (err)
return err;
} else if (!rcu_access_pointer(sk->sk_reuseport_cb)) {
......@@ -7013,3 +7013,270 @@ int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
release_sock(sk);
return ret;
}
#ifdef CONFIG_INET
struct sk_reuseport_kern {
struct sk_buff *skb;
struct sock *sk;
struct sock *selected_sk;
void *data_end;
u32 hash;
u32 reuseport_id;
bool bind_inany;
};
static void bpf_init_reuseport_kern(struct sk_reuseport_kern *reuse_kern,
struct sock_reuseport *reuse,
struct sock *sk, struct sk_buff *skb,
u32 hash)
{
reuse_kern->skb = skb;
reuse_kern->sk = sk;
reuse_kern->selected_sk = NULL;
reuse_kern->data_end = skb->data + skb_headlen(skb);
reuse_kern->hash = hash;
reuse_kern->reuseport_id = reuse->reuseport_id;
reuse_kern->bind_inany = reuse->bind_inany;
}
struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
struct bpf_prog *prog, struct sk_buff *skb,
u32 hash)
{
struct sk_reuseport_kern reuse_kern;
enum sk_action action;
bpf_init_reuseport_kern(&reuse_kern, reuse, sk, skb, hash);
action = BPF_PROG_RUN(prog, &reuse_kern);
if (action == SK_PASS)
return reuse_kern.selected_sk;
else
return ERR_PTR(-ECONNREFUSED);
}
BPF_CALL_4(sk_select_reuseport, struct sk_reuseport_kern *, reuse_kern,
struct bpf_map *, map, void *, key, u32, flags)
{
struct sock_reuseport *reuse;
struct sock *selected_sk;
selected_sk = map->ops->map_lookup_elem(map, key);
if (!selected_sk)
return -ENOENT;
reuse = rcu_dereference(selected_sk->sk_reuseport_cb);
if (!reuse)
/* selected_sk is unhashed (e.g. by close()) after the
* above map_lookup_elem(). Treat selected_sk has already
* been removed from the map.
*/
return -ENOENT;
if (unlikely(reuse->reuseport_id != reuse_kern->reuseport_id)) {
struct sock *sk;
if (unlikely(!reuse_kern->reuseport_id))
/* There is a small race between adding the
* sk to the map and setting the
* reuse_kern->reuseport_id.
* Treat it as the sk has not been added to
* the bpf map yet.
*/
return -ENOENT;
sk = reuse_kern->sk;
if (sk->sk_protocol != selected_sk->sk_protocol)
return -EPROTOTYPE;
else if (sk->sk_family != selected_sk->sk_family)
return -EAFNOSUPPORT;
/* Catch all. Likely bound to a different sockaddr. */
return -EBADFD;
}
reuse_kern->selected_sk = selected_sk;
return 0;
}
static const struct bpf_func_proto sk_select_reuseport_proto = {
.func = sk_select_reuseport,
.gpl_only = false,
.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,
};
BPF_CALL_4(sk_reuseport_load_bytes,
const struct sk_reuseport_kern *, reuse_kern, u32, offset,
void *, to, u32, len)
{
return ____bpf_skb_load_bytes(reuse_kern->skb, offset, to, len);
}
static const struct bpf_func_proto sk_reuseport_load_bytes_proto = {
.func = sk_reuseport_load_bytes,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
.arg3_type = ARG_PTR_TO_UNINIT_MEM,
.arg4_type = ARG_CONST_SIZE,
};
BPF_CALL_5(sk_reuseport_load_bytes_relative,
const struct sk_reuseport_kern *, reuse_kern, u32, offset,
void *, to, u32, len, u32, start_header)
{
return ____bpf_skb_load_bytes_relative(reuse_kern->skb, offset, to,
len, start_header);
}
static const struct bpf_func_proto sk_reuseport_load_bytes_relative_proto = {
.func = sk_reuseport_load_bytes_relative,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
.arg3_type = ARG_PTR_TO_UNINIT_MEM,
.arg4_type = ARG_CONST_SIZE,
.arg5_type = ARG_ANYTHING,
};
static const struct bpf_func_proto *
sk_reuseport_func_proto(enum bpf_func_id func_id,
const struct bpf_prog *prog)
{
switch (func_id) {
case BPF_FUNC_sk_select_reuseport:
return &sk_select_reuseport_proto;
case BPF_FUNC_skb_load_bytes:
return &sk_reuseport_load_bytes_proto;
case BPF_FUNC_skb_load_bytes_relative:
return &sk_reuseport_load_bytes_relative_proto;
default:
return bpf_base_func_proto(func_id);
}
}
static bool
sk_reuseport_is_valid_access(int off, int size,
enum bpf_access_type type,
const struct bpf_prog *prog,
struct bpf_insn_access_aux *info)
{
const u32 size_default = sizeof(__u32);
if (off < 0 || off >= sizeof(struct sk_reuseport_md) ||
off % size || type != BPF_READ)
return false;
switch (off) {
case offsetof(struct sk_reuseport_md, data):
info->reg_type = PTR_TO_PACKET;
return size == sizeof(__u64);
case offsetof(struct sk_reuseport_md, data_end):
info->reg_type = PTR_TO_PACKET_END;
return size == sizeof(__u64);
case offsetof(struct sk_reuseport_md, hash):
return size == size_default;
/* Fields that allow narrowing */
case offsetof(struct sk_reuseport_md, eth_protocol):
if (size < FIELD_SIZEOF(struct sk_buff, protocol))
return false;
case offsetof(struct sk_reuseport_md, ip_protocol):
case offsetof(struct sk_reuseport_md, bind_inany):
case offsetof(struct sk_reuseport_md, len):
bpf_ctx_record_field_size(info, size_default);
return bpf_ctx_narrow_access_ok(off, size, size_default);
default:
return false;
}
}
#define SK_REUSEPORT_LOAD_FIELD(F) ({ \
*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_reuseport_kern, F), \
si->dst_reg, si->src_reg, \
bpf_target_off(struct sk_reuseport_kern, F, \
FIELD_SIZEOF(struct sk_reuseport_kern, F), \
target_size)); \
})
#define SK_REUSEPORT_LOAD_SKB_FIELD(SKB_FIELD) \
SOCK_ADDR_LOAD_NESTED_FIELD(struct sk_reuseport_kern, \
struct sk_buff, \
skb, \
SKB_FIELD)
#define SK_REUSEPORT_LOAD_SK_FIELD_SIZE_OFF(SK_FIELD, BPF_SIZE, EXTRA_OFF) \
SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF(struct sk_reuseport_kern, \
struct sock, \
sk, \
SK_FIELD, BPF_SIZE, EXTRA_OFF)
static u32 sk_reuseport_convert_ctx_access(enum bpf_access_type type,
const struct bpf_insn *si,
struct bpf_insn *insn_buf,
struct bpf_prog *prog,
u32 *target_size)
{
struct bpf_insn *insn = insn_buf;
switch (si->off) {
case offsetof(struct sk_reuseport_md, data):
SK_REUSEPORT_LOAD_SKB_FIELD(data);
break;
case offsetof(struct sk_reuseport_md, len):
SK_REUSEPORT_LOAD_SKB_FIELD(len);
break;
case offsetof(struct sk_reuseport_md, eth_protocol):
SK_REUSEPORT_LOAD_SKB_FIELD(protocol);
break;
case offsetof(struct sk_reuseport_md, ip_protocol):
BUILD_BUG_ON(hweight_long(SK_FL_PROTO_MASK) != BITS_PER_BYTE);
SK_REUSEPORT_LOAD_SK_FIELD_SIZE_OFF(__sk_flags_offset,
BPF_W, 0);
*insn++ = BPF_ALU32_IMM(BPF_AND, si->dst_reg, SK_FL_PROTO_MASK);
*insn++ = BPF_ALU32_IMM(BPF_RSH, si->dst_reg,
SK_FL_PROTO_SHIFT);
/* SK_FL_PROTO_MASK and SK_FL_PROTO_SHIFT are endian
* aware. No further narrowing or masking is needed.
*/
*target_size = 1;
break;
case offsetof(struct sk_reuseport_md, data_end):
SK_REUSEPORT_LOAD_FIELD(data_end);
break;
case offsetof(struct sk_reuseport_md, hash):
SK_REUSEPORT_LOAD_FIELD(hash);
break;
case offsetof(struct sk_reuseport_md, bind_inany):
SK_REUSEPORT_LOAD_FIELD(bind_inany);
break;
}
return insn - insn_buf;
}
const struct bpf_verifier_ops sk_reuseport_verifier_ops = {
.get_func_proto = sk_reuseport_func_proto,
.is_valid_access = sk_reuseport_is_valid_access,
.convert_ctx_access = sk_reuseport_convert_ctx_access,
};
const struct bpf_prog_ops sk_reuseport_prog_ops = {
};
#endif /* CONFIG_INET */
......@@ -51,7 +51,7 @@ static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
return reuse;
}
int reuseport_alloc(struct sock *sk)
int reuseport_alloc(struct sock *sk, bool bind_inany)
{
struct sock_reuseport *reuse;
......@@ -63,9 +63,17 @@ int reuseport_alloc(struct sock *sk)
/* Allocation attempts can occur concurrently via the setsockopt path
* and the bind/hash path. Nothing to do when we lose the race.
*/
if (rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock)))
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
if (reuse) {
/* Only set reuse->bind_inany if the bind_inany is true.
* Otherwise, it will overwrite the reuse->bind_inany
* which was set by the bind/hash path.
*/
if (bind_inany)
reuse->bind_inany = bind_inany;
goto out;
}
reuse = __reuseport_alloc(INIT_SOCKS);
if (!reuse) {
......@@ -75,6 +83,7 @@ int reuseport_alloc(struct sock *sk)
reuse->socks[0] = sk;
reuse->num_socks = 1;
reuse->bind_inany = bind_inany;
rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
out:
......@@ -101,6 +110,7 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
more_reuse->num_socks = reuse->num_socks;
more_reuse->prog = reuse->prog;
more_reuse->reuseport_id = reuse->reuseport_id;
more_reuse->bind_inany = reuse->bind_inany;
memcpy(more_reuse->socks, reuse->socks,
reuse->num_socks * sizeof(struct sock *));
......@@ -136,12 +146,12 @@ static void reuseport_free_rcu(struct rcu_head *head)
* @sk2: Socket belonging to the existing reuseport group.
* May return ENOMEM and not add socket to group under memory pressure.
*/
int reuseport_add_sock(struct sock *sk, struct sock *sk2)
int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
{
struct sock_reuseport *old_reuse, *reuse;
if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
int err = reuseport_alloc(sk2);
int err = reuseport_alloc(sk2, bind_inany);
if (err)
return err;
......
......@@ -107,6 +107,15 @@ bool inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
}
EXPORT_SYMBOL(inet_rcv_saddr_equal);
bool inet_rcv_saddr_any(const struct sock *sk)
{
#if IS_ENABLED(CONFIG_IPV6)
if (sk->sk_family == AF_INET6)
return ipv6_addr_any(&sk->sk_v6_rcv_saddr);
#endif
return !sk->sk_rcv_saddr;
}
void inet_get_local_port_range(struct net *net, int *low, int *high)
{
unsigned int seq;
......
......@@ -567,10 +567,11 @@ static int inet_reuseport_add_sock(struct sock *sk,
inet_csk(sk2)->icsk_bind_hash == tb &&
sk2->sk_reuseport && uid_eq(uid, sock_i_uid(sk2)) &&
inet_rcv_saddr_equal(sk, sk2, false))
return reuseport_add_sock(sk, sk2);
return reuseport_add_sock(sk, sk2,
inet_rcv_saddr_any(sk));
}
return reuseport_alloc(sk);
return reuseport_alloc(sk, inet_rcv_saddr_any(sk));
}
int __inet_hash(struct sock *sk, struct sock *osk)
......
......@@ -221,11 +221,12 @@ static int udp_reuseport_add_sock(struct sock *sk, struct udp_hslot *hslot)
(sk2->sk_bound_dev_if == sk->sk_bound_dev_if) &&
sk2->sk_reuseport && uid_eq(uid, sock_i_uid(sk2)) &&
inet_rcv_saddr_equal(sk, sk2, false)) {
return reuseport_add_sock(sk, sk2);
return reuseport_add_sock(sk, sk2,
inet_rcv_saddr_any(sk));
}
}
return reuseport_alloc(sk);
return reuseport_alloc(sk, inet_rcv_saddr_any(sk));
}
/**
......
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