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bpf: Add new cgroup attach type to enable sock modifications

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Add new cgroup based program type, BPF_PROG_TYPE_CGROUP_SOCK. Similar to
BPF_PROG_TYPE_CGROUP_SKB programs can be attached to a cgroup and run
any time a process in the cgroup opens an AF_INET or AF_INET6 socket.
Currently only sk_bound_dev_if is exported to userspace for modification
by a bpf program.

This allows a cgroup to be configured such that AF_INET{6} sockets opened
by processes are automatically bound to a specific device. In turn, this
enables the running of programs that do not support SO_BINDTODEVICE in a
specific VRF context / L3 domain.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2016-12-01 08:48:04 -08:00 committed by David S. Miller
parent b2cd12574a
commit 6102365876
7 changed files with 138 additions and 2 deletions
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14
include/linux/bpf-cgroup.h
View File

@ -40,6 +40,9 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
struct sk_buff *skb,
enum bpf_attach_type type);
int __cgroup_bpf_run_filter_sk(struct sock *sk,
enum bpf_attach_type type);
/* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */
#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb) \
({ \
@ -63,6 +66,16 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
__ret; \
})
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) \
({ \
int __ret = 0; \
if (cgroup_bpf_enabled && sk) { \
__ret = __cgroup_bpf_run_filter_sk(sk, \
BPF_CGROUP_INET_SOCK_CREATE); \
} \
__ret; \
})
#else
struct cgroup_bpf {};
@ -72,6 +85,7 @@ static inline void cgroup_bpf_inherit(struct cgroup *cgrp,
#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) ({ 0; })
#endif /* CONFIG_CGROUP_BPF */

6
include/uapi/linux/bpf.h
View File

@ -101,6 +101,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_XDP,
BPF_PROG_TYPE_PERF_EVENT,
BPF_PROG_TYPE_CGROUP_SKB,
BPF_PROG_TYPE_CGROUP_SOCK,
BPF_PROG_TYPE_LWT_IN,
BPF_PROG_TYPE_LWT_OUT,
BPF_PROG_TYPE_LWT_XMIT,
@ -109,6 +110,7 @@ enum bpf_prog_type {
enum bpf_attach_type {
BPF_CGROUP_INET_INGRESS,
BPF_CGROUP_INET_EGRESS,
BPF_CGROUP_INET_SOCK_CREATE,
__MAX_BPF_ATTACH_TYPE
};
@ -567,6 +569,10 @@ enum bpf_ret_code {
/* >127 are reserved for prog type specific return codes */
};
struct bpf_sock {
__u32 bound_dev_if;
};
/* User return codes for XDP prog type.
* A valid XDP program must return one of these defined values. All other
* return codes are reserved for future use. Unknown return codes will result

33
kernel/bpf/cgroup.c
View File

@ -165,3 +165,36 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
return ret;
}
EXPORT_SYMBOL(__cgroup_bpf_run_filter_skb);
/**
* __cgroup_bpf_run_filter_sk() - Run a program on a sock
* @sk: sock structure to manipulate
* @type: The type of program to be exectuted
*
* socket is passed is expected to be of type INET or INET6.
*
* The program type passed in via @type must be suitable for sock
* filtering. No further check is performed to assert that.
*
* This function will return %-EPERM if any if an attached program was found
* and if it returned != 1 during execution. In all other cases, 0 is returned.
*/
int __cgroup_bpf_run_filter_sk(struct sock *sk,
enum bpf_attach_type type)
{
struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
struct bpf_prog *prog;
int ret = 0;
rcu_read_lock();
prog = rcu_dereference(cgrp->bpf.effective[type]);
if (prog)
ret = BPF_PROG_RUN(prog, sk) == 1 ? 0 : -EPERM;
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);

5
kernel/bpf/syscall.c
View File

@ -869,7 +869,9 @@ static int bpf_prog_attach(const union bpf_attr *attr)
case BPF_CGROUP_INET_EGRESS:
ptype = BPF_PROG_TYPE_CGROUP_SKB;
break;
case BPF_CGROUP_INET_SOCK_CREATE:
ptype = BPF_PROG_TYPE_CGROUP_SOCK;
break;
default:
return -EINVAL;
}
@ -905,6 +907,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
switch (attr->attach_type) {
case BPF_CGROUP_INET_INGRESS:
case BPF_CGROUP_INET_EGRESS:
case BPF_CGROUP_INET_SOCK_CREATE:
cgrp = cgroup_get_from_fd(attr->target_fd);
if (IS_ERR(cgrp))
return PTR_ERR(cgrp);

62
net/core/filter.c
View File

@ -2818,6 +2818,32 @@ static bool lwt_is_valid_access(int off, int size,
return __is_valid_access(off, size, type);
}
static bool sock_filter_is_valid_access(int off, int size,
enum bpf_access_type type,
enum bpf_reg_type *reg_type)
{
if (type == BPF_WRITE) {
switch (off) {
case offsetof(struct bpf_sock, bound_dev_if):
break;
default:
return false;
}
}
if (off < 0 || off + size > sizeof(struct bpf_sock))
return false;
/* The verifier guarantees that size > 0. */
if (off % size != 0)
return false;
if (size != sizeof(__u32))
return false;
return true;
}
static int tc_cls_act_prologue(struct bpf_insn *insn_buf, bool direct_write,
const struct bpf_prog *prog)
{
@ -3076,6 +3102,30 @@ static u32 sk_filter_convert_ctx_access(enum bpf_access_type type, int dst_reg,
return insn - insn_buf;
}
static u32 sock_filter_convert_ctx_access(enum bpf_access_type type,
int dst_reg, int src_reg,
int ctx_off,
struct bpf_insn *insn_buf,
struct bpf_prog *prog)
{
struct bpf_insn *insn = insn_buf;
switch (ctx_off) {
case offsetof(struct bpf_sock, bound_dev_if):
BUILD_BUG_ON(FIELD_SIZEOF(struct sock, sk_bound_dev_if) != 4);
if (type == BPF_WRITE)
*insn++ = BPF_STX_MEM(BPF_W, dst_reg, src_reg,
offsetof(struct sock, sk_bound_dev_if));
else
*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
offsetof(struct sock, sk_bound_dev_if));
break;
}
return insn - insn_buf;
}
static u32 tc_cls_act_convert_ctx_access(enum bpf_access_type type, int dst_reg,
int src_reg, int ctx_off,
struct bpf_insn *insn_buf,
@ -3162,6 +3212,12 @@ static const struct bpf_verifier_ops lwt_xmit_ops = {
.gen_prologue = tc_cls_act_prologue,
};
static const struct bpf_verifier_ops cg_sock_ops = {
.get_func_proto = sk_filter_func_proto,
.is_valid_access = sock_filter_is_valid_access,
.convert_ctx_access = sock_filter_convert_ctx_access,
};
static struct bpf_prog_type_list sk_filter_type __read_mostly = {
.ops = &sk_filter_ops,
.type = BPF_PROG_TYPE_SOCKET_FILTER,
@ -3202,6 +3258,11 @@ static struct bpf_prog_type_list lwt_xmit_type __read_mostly = {
.type = BPF_PROG_TYPE_LWT_XMIT,
};
static struct bpf_prog_type_list cg_sock_type __read_mostly = {
.ops = &cg_sock_ops,
.type = BPF_PROG_TYPE_CGROUP_SOCK
};
static int __init register_sk_filter_ops(void)
{
bpf_register_prog_type(&sk_filter_type);
@ -3209,6 +3270,7 @@ static int __init register_sk_filter_ops(void)
bpf_register_prog_type(&sched_act_type);
bpf_register_prog_type(&xdp_type);
bpf_register_prog_type(&cg_skb_type);
bpf_register_prog_type(&cg_sock_type);
bpf_register_prog_type(&lwt_in_type);
bpf_register_prog_type(&lwt_out_type);
bpf_register_prog_type(&lwt_xmit_type);

12
net/ipv4/af_inet.c
View File

@ -374,8 +374,18 @@ static int inet_create(struct net *net, struct socket *sock, int protocol,
if (sk->sk_prot->init) {
err = sk->sk_prot->init(sk);
if (err)
if (err) {
sk_common_release(sk);
goto out;
}
}
if (!kern) {
err = BPF_CGROUP_RUN_PROG_INET_SOCK(sk);
if (err) {
sk_common_release(sk);
goto out;
}
}
out:
return err;

8
net/ipv6/af_inet6.c
View File

@ -258,6 +258,14 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
goto out;
}
}
if (!kern) {
err = BPF_CGROUP_RUN_PROG_INET_SOCK(sk);
if (err) {
sk_common_release(sk);
goto out;
}
}
out:
return err;
out_rcu_unlock: