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flow_dissector: implements flow dissector BPF hook 

Adds a hook for programs of type BPF_PROG_TYPE_FLOW_DISSECTOR and
attach type BPF_FLOW_DISSECTOR that is executed in the flow dissector
path. The BPF program is per-network namespace.

Signed-off-by: Petar Penkov <ppenkov@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Petar Penkov 2018-09-14 07:46:18 -07:00 committed by Alexei Starovoitov
parent 1edb6e035e
commit d58e468b11
10 changed files with 291 additions and 3 deletions
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1
include/linux/bpf.h
View File

@ -212,6 +212,7 @@ enum bpf_reg_type {
PTR_TO_PACKET_META, /* skb->data - meta_len */
PTR_TO_PACKET, /* reg points to skb->data */
PTR_TO_PACKET_END, /* skb->data + headlen */
PTR_TO_FLOW_KEYS, /* reg points to bpf_flow_keys */
};
/* The information passed from prog-specific *_is_valid_access

1
include/linux/bpf_types.h
View File

@ -32,6 +32,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2)
#ifdef CONFIG_INET
BPF_PROG_TYPE(BPF_PROG_TYPE_SK_REUSEPORT, sk_reuseport)
#endif
BPF_PROG_TYPE(BPF_PROG_TYPE_FLOW_DISSECTOR, flow_dissector)
BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops)
BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops)

7
include/linux/skbuff.h
View File

@ -243,6 +243,8 @@ struct scatterlist;
struct pipe_inode_info;
struct iov_iter;
struct napi_struct;
struct bpf_prog;
union bpf_attr;
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
struct nf_conntrack {
@ -1192,6 +1194,11 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
const struct flow_dissector_key *key,
unsigned int key_count);
int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
struct bpf_prog *prog);
int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr);
bool __skb_flow_dissect(const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
void *target_container,

3
include/net/net_namespace.h
View File

@ -43,6 +43,7 @@ struct ctl_table_header;
struct net_generic;
struct uevent_sock;
struct netns_ipvs;
struct bpf_prog;
#define NETDEV_HASHBITS 8
@ -145,6 +146,8 @@ struct net {
#endif
struct net_generic __rcu *gen;
struct bpf_prog __rcu *flow_dissector_prog;
/* Note : following structs are cache line aligned */
#ifdef CONFIG_XFRM
struct netns_xfrm xfrm;

12
include/net/sch_generic.h
View File

@ -19,6 +19,7 @@ struct Qdisc_ops;
struct qdisc_walker;
struct tcf_walker;
struct module;
struct bpf_flow_keys;
typedef int tc_setup_cb_t(enum tc_setup_type type,
void *type_data, void *cb_priv);
@ -307,9 +308,14 @@ struct tcf_proto {
};
struct qdisc_skb_cb {
unsigned int pkt_len;
u16 slave_dev_queue_mapping;
u16 tc_classid;
union {
struct {
unsigned int pkt_len;
u16 slave_dev_queue_mapping;
u16 tc_classid;
};
struct bpf_flow_keys *flow_keys;
};
#define QDISC_CB_PRIV_LEN 20
unsigned char data[QDISC_CB_PRIV_LEN];
};

26
include/uapi/linux/bpf.h
View File

@ -152,6 +152,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_LWT_SEG6LOCAL,
BPF_PROG_TYPE_LIRC_MODE2,
BPF_PROG_TYPE_SK_REUSEPORT,
BPF_PROG_TYPE_FLOW_DISSECTOR,
};
enum bpf_attach_type {
@ -172,6 +173,7 @@ enum bpf_attach_type {
BPF_CGROUP_UDP4_SENDMSG,
BPF_CGROUP_UDP6_SENDMSG,
BPF_LIRC_MODE2,
BPF_FLOW_DISSECTOR,
__MAX_BPF_ATTACH_TYPE
};
@ -2333,6 +2335,7 @@ struct __sk_buff {
/* ... here. */
__u32 data_meta;
struct bpf_flow_keys *flow_keys;
};
struct bpf_tunnel_key {
@ -2778,4 +2781,27 @@ enum bpf_task_fd_type {
BPF_FD_TYPE_URETPROBE, /* filename + offset */
};
struct bpf_flow_keys {
__u16 nhoff;
__u16 thoff;
__u16 addr_proto; /* ETH_P_* of valid addrs */
__u8 is_frag;
__u8 is_first_frag;
__u8 is_encap;
__u8 ip_proto;
__be16 n_proto;
__be16 sport;
__be16 dport;
union {
struct {
__be32 ipv4_src;
__be32 ipv4_dst;
};
struct {
__u32 ipv6_src[4]; /* in6_addr; network order */
__u32 ipv6_dst[4]; /* in6_addr; network order */
};
};
};
#endif /* _UAPI__LINUX_BPF_H__ */

8
kernel/bpf/syscall.c
View File

@ -1615,6 +1615,9 @@ static int bpf_prog_attach(const union bpf_attr *attr)
case BPF_LIRC_MODE2:
ptype = BPF_PROG_TYPE_LIRC_MODE2;
break;
case BPF_FLOW_DISSECTOR:
ptype = BPF_PROG_TYPE_FLOW_DISSECTOR;
break;
default:
return -EINVAL;
}
@ -1636,6 +1639,9 @@ static int bpf_prog_attach(const union bpf_attr *attr)
case BPF_PROG_TYPE_LIRC_MODE2:
ret = lirc_prog_attach(attr, prog);
break;
case BPF_PROG_TYPE_FLOW_DISSECTOR:
ret = skb_flow_dissector_bpf_prog_attach(attr, prog);
break;
default:
ret = cgroup_bpf_prog_attach(attr, ptype, prog);
}
@ -1688,6 +1694,8 @@ static int bpf_prog_detach(const union bpf_attr *attr)
return sockmap_get_from_fd(attr, BPF_PROG_TYPE_SK_SKB, NULL);
case BPF_LIRC_MODE2:
return lirc_prog_detach(attr);
case BPF_FLOW_DISSECTOR:
return skb_flow_dissector_bpf_prog_detach(attr);
default:
return -EINVAL;
}

32
kernel/bpf/verifier.c
View File

@ -261,6 +261,7 @@ static const char * const reg_type_str[] = {
[PTR_TO_PACKET] = "pkt",
[PTR_TO_PACKET_META] = "pkt_meta",
[PTR_TO_PACKET_END] = "pkt_end",
[PTR_TO_FLOW_KEYS] = "flow_keys",
};
static char slot_type_char[] = {
@ -965,6 +966,7 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
case PTR_TO_PACKET_END:
case PTR_TO_FLOW_KEYS:
case CONST_PTR_TO_MAP:
return true;
default:
@ -1238,6 +1240,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
case BPF_PROG_TYPE_LWT_XMIT:
case BPF_PROG_TYPE_SK_SKB:
case BPF_PROG_TYPE_SK_MSG:
case BPF_PROG_TYPE_FLOW_DISSECTOR:
if (meta)
return meta->pkt_access;
@ -1321,6 +1324,18 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off,
return -EACCES;
}
static int check_flow_keys_access(struct bpf_verifier_env *env, int off,
int size)
{
if (size < 0 || off < 0 ||
(u64)off + size > sizeof(struct bpf_flow_keys)) {
verbose(env, "invalid access to flow keys off=%d size=%d\n",
off, size);
return -EACCES;
}
return 0;
}
static bool __is_pointer_value(bool allow_ptr_leaks,
const struct bpf_reg_state *reg)
{
@ -1422,6 +1437,9 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
* right in front, treat it the very same way.
*/
return check_pkt_ptr_alignment(env, reg, off, size, strict);
case PTR_TO_FLOW_KEYS:
pointer_desc = "flow keys ";
break;
case PTR_TO_MAP_VALUE:
pointer_desc = "value ";
break;
@ -1692,6 +1710,17 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
err = check_packet_access(env, regno, off, size, false);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else if (reg->type == PTR_TO_FLOW_KEYS) {
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
verbose(env, "R%d leaks addr into flow keys\n",
value_regno);
return -EACCES;
}
err = check_flow_keys_access(env, off, size);
if (!err && t == BPF_READ && value_regno >= 0)
mark_reg_unknown(env, regs, value_regno);
} else {
verbose(env, "R%d invalid mem access '%s'\n", regno,
reg_type_str[reg->type]);
@ -1839,6 +1868,8 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
case PTR_TO_PACKET_META:
return check_packet_access(env, regno, reg->off, access_size,
zero_size_allowed);
case PTR_TO_FLOW_KEYS:
return check_flow_keys_access(env, reg->off, access_size);
case PTR_TO_MAP_VALUE:
return check_map_access(env, regno, reg->off, access_size,
zero_size_allowed);
@ -4366,6 +4397,7 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
case PTR_TO_CTX:
case CONST_PTR_TO_MAP:
case PTR_TO_PACKET_END:
case PTR_TO_FLOW_KEYS:
/* Only valid matches are exact, which memcmp() above
* would have accepted
*/

70
net/core/filter.c
View File

@ -5123,6 +5123,17 @@ sk_skb_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
}
}
static const struct bpf_func_proto *
flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
switch (func_id) {
case BPF_FUNC_skb_load_bytes:
return &bpf_skb_load_bytes_proto;
default:
return bpf_base_func_proto(func_id);
}
}
static const struct bpf_func_proto *
lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@ -5241,6 +5252,10 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
if (size != size_default)
return false;
break;
case bpf_ctx_range(struct __sk_buff, flow_keys):
if (size != sizeof(struct bpf_flow_keys *))
return false;
break;
default:
/* Only narrow read access allowed for now. */
if (type == BPF_WRITE) {
@ -5266,6 +5281,7 @@ static bool sk_filter_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, data):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range(struct __sk_buff, data_end):
case bpf_ctx_range(struct __sk_buff, flow_keys):
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
return false;
}
@ -5291,6 +5307,7 @@ static bool lwt_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, tc_classid):
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range(struct __sk_buff, flow_keys):
return false;
}
@ -5501,6 +5518,7 @@ static bool tc_cls_act_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, data_end):
info->reg_type = PTR_TO_PACKET_END;
break;
case bpf_ctx_range(struct __sk_buff, flow_keys):
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
return false;
}
@ -5702,6 +5720,7 @@ static bool sk_skb_is_valid_access(int off, int size,
switch (off) {
case bpf_ctx_range(struct __sk_buff, tc_classid):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range(struct __sk_buff, flow_keys):
return false;
}
@ -5761,6 +5780,39 @@ static bool sk_msg_is_valid_access(int off, int size,
return true;
}
static bool flow_dissector_is_valid_access(int off, int size,
enum bpf_access_type type,
const struct bpf_prog *prog,
struct bpf_insn_access_aux *info)
{
if (type == BPF_WRITE) {
switch (off) {
case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
break;
default:
return false;
}
}
switch (off) {
case bpf_ctx_range(struct __sk_buff, data):
info->reg_type = PTR_TO_PACKET;
break;
case bpf_ctx_range(struct __sk_buff, data_end):
info->reg_type = PTR_TO_PACKET_END;
break;
case bpf_ctx_range(struct __sk_buff, flow_keys):
info->reg_type = PTR_TO_FLOW_KEYS;
break;
case bpf_ctx_range(struct __sk_buff, tc_classid):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
return false;
}
return bpf_skb_is_valid_access(off, size, type, prog, info);
}
static u32 bpf_convert_ctx_access(enum bpf_access_type type,
const struct bpf_insn *si,
struct bpf_insn *insn_buf,
@ -6055,6 +6107,15 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
bpf_target_off(struct sock_common,
skc_num, 2, target_size));
break;
case offsetof(struct __sk_buff, flow_keys):
off = si->off;
off -= offsetof(struct __sk_buff, flow_keys);
off += offsetof(struct sk_buff, cb);
off += offsetof(struct qdisc_skb_cb, flow_keys);
*insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg,
si->src_reg, off);
break;
}
return insn - insn_buf;
@ -7018,6 +7079,15 @@ const struct bpf_verifier_ops sk_msg_verifier_ops = {
const struct bpf_prog_ops sk_msg_prog_ops = {
};
const struct bpf_verifier_ops flow_dissector_verifier_ops = {
.get_func_proto = flow_dissector_func_proto,
.is_valid_access = flow_dissector_is_valid_access,
.convert_ctx_access = bpf_convert_ctx_access,
};
const struct bpf_prog_ops flow_dissector_prog_ops = {
};
int sk_detach_filter(struct sock *sk)
{
int ret = -ENOENT;

134
net/core/flow_dissector.c
View File

@ -25,6 +25,9 @@
#include <net/flow_dissector.h>
#include <scsi/fc/fc_fcoe.h>
#include <uapi/linux/batadv_packet.h>
#include <linux/bpf.h>
static DEFINE_MUTEX(flow_dissector_mutex);
static void dissector_set_key(struct flow_dissector *flow_dissector,
enum flow_dissector_key_id key_id)
@ -62,6 +65,44 @@ void skb_flow_dissector_init(struct flow_dissector *flow_dissector,
}
EXPORT_SYMBOL(skb_flow_dissector_init);
int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr,
struct bpf_prog *prog)
{
struct bpf_prog *attached;
struct net *net;
net = current->nsproxy->net_ns;
mutex_lock(&flow_dissector_mutex);
attached = rcu_dereference_protected(net->flow_dissector_prog,
lockdep_is_held(&flow_dissector_mutex));
if (attached) {
/* Only one BPF program can be attached at a time */
mutex_unlock(&flow_dissector_mutex);
return -EEXIST;
}
rcu_assign_pointer(net->flow_dissector_prog, prog);
mutex_unlock(&flow_dissector_mutex);
return 0;
}
int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
{
struct bpf_prog *attached;
struct net *net;
net = current->nsproxy->net_ns;
mutex_lock(&flow_dissector_mutex);
attached = rcu_dereference_protected(net->flow_dissector_prog,
lockdep_is_held(&flow_dissector_mutex));
if (!attached) {
mutex_unlock(&flow_dissector_mutex);
return -ENOENT;
}
bpf_prog_put(attached);
RCU_INIT_POINTER(net->flow_dissector_prog, NULL);
mutex_unlock(&flow_dissector_mutex);
return 0;
}
/**
* skb_flow_get_be16 - extract be16 entity
* @skb: sk_buff to extract from
@ -588,6 +629,60 @@ static bool skb_flow_dissect_allowed(int *num_hdrs)
return (*num_hdrs <= MAX_FLOW_DISSECT_HDRS);
}
static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
struct flow_dissector *flow_dissector,
void *target_container)
{
struct flow_dissector_key_control *key_control;
struct flow_dissector_key_basic *key_basic;
struct flow_dissector_key_addrs *key_addrs;
struct flow_dissector_key_ports *key_ports;
key_control = skb_flow_dissector_target(flow_dissector,
FLOW_DISSECTOR_KEY_CONTROL,
target_container);
key_control->thoff = flow_keys->thoff;
if (flow_keys->is_frag)
key_control->flags |= FLOW_DIS_IS_FRAGMENT;
if (flow_keys->is_first_frag)
key_control->flags |= FLOW_DIS_FIRST_FRAG;
if (flow_keys->is_encap)
key_control->flags |= FLOW_DIS_ENCAPSULATION;
key_basic = skb_flow_dissector_target(flow_dissector,
FLOW_DISSECTOR_KEY_BASIC,
target_container);
key_basic->n_proto = flow_keys->n_proto;
key_basic->ip_proto = flow_keys->ip_proto;
if (flow_keys->addr_proto == ETH_P_IP &&
dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IPV4_ADDRS)) {
key_addrs = skb_flow_dissector_target(flow_dissector,
FLOW_DISSECTOR_KEY_IPV4_ADDRS,
target_container);
key_addrs->v4addrs.src = flow_keys->ipv4_src;
key_addrs->v4addrs.dst = flow_keys->ipv4_dst;
key_control->addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
} else if (flow_keys->addr_proto == ETH_P_IPV6 &&
dissector_uses_key(flow_dissector,
FLOW_DISSECTOR_KEY_IPV6_ADDRS)) {
key_addrs = skb_flow_dissector_target(flow_dissector,
FLOW_DISSECTOR_KEY_IPV6_ADDRS,
target_container);
memcpy(&key_addrs->v6addrs, &flow_keys->ipv6_src,
sizeof(key_addrs->v6addrs));
key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
}
if (dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_PORTS)) {
key_ports = skb_flow_dissector_target(flow_dissector,
FLOW_DISSECTOR_KEY_PORTS,
target_container);
key_ports->src = flow_keys->sport;
key_ports->dst = flow_keys->dport;
}
}
/**
* __skb_flow_dissect - extract the flow_keys struct and return it
* @skb: sk_buff to extract the flow from, can be NULL if the rest are specified
@ -619,6 +714,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
struct flow_dissector_key_vlan *key_vlan;
enum flow_dissect_ret fdret;
enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
struct bpf_prog *attached;
int num_hdrs = 0;
u8 ip_proto = 0;
bool ret;
@ -658,6 +754,44 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
FLOW_DISSECTOR_KEY_BASIC,
target_container);
rcu_read_lock();
attached = skb ? rcu_dereference(dev_net(skb->dev)->flow_dissector_prog)
: NULL;
if (attached) {
/* Note that even though the const qualifier is discarded
* throughout the execution of the BPF program, all changes(the
* control block) are reverted after the BPF program returns.
* Therefore, __skb_flow_dissect does not alter the skb.
*/
struct bpf_flow_keys flow_keys = {};
struct bpf_skb_data_end cb_saved;
struct bpf_skb_data_end *cb;
u32 result;
cb = (struct bpf_skb_data_end *)skb->cb;
/* Save Control Block */
memcpy(&cb_saved, cb, sizeof(cb_saved));
memset(cb, 0, sizeof(cb_saved));
/* Pass parameters to the BPF program */
cb->qdisc_cb.flow_keys = &flow_keys;
flow_keys.nhoff = nhoff;
bpf_compute_data_pointers((struct sk_buff *)skb);
result = BPF_PROG_RUN(attached, skb);
/* Restore state */
memcpy(cb, &cb_saved, sizeof(cb_saved));
__skb_flow_bpf_to_target(&flow_keys, flow_dissector,
target_container);
key_control->thoff = min_t(u16, key_control->thoff, skb->len);
rcu_read_unlock();
return result == BPF_OK;
}
rcu_read_unlock();
if (dissector_uses_key(flow_dissector,
FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
struct ethhdr *eth = eth_hdr(skb);