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bpf: Add BPF_CGROUP_INET_SOCK_RELEASE hook

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Sometimes it's handy to know when the socket gets freed. In
particular, we'd like to try to use a smarter allocation of
ports for bpf_bind and explore the possibility of limiting
the number of SOCK_DGRAM sockets the process can have.

Implement BPF_CGROUP_INET_SOCK_RELEASE hook that triggers on
inet socket release. It triggers only for userspace sockets
(not in-kernel ones) and therefore has the same semantics as
the existing BPF_CGROUP_INET_SOCK_CREATE.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200706230128.4073544-2-sdf@google.com
This commit is contained in:
Stanislav Fomichev 2020-07-06 16:01:25 -07:00 committed by Daniel Borkmann
parent 4e48978cd2
commit f5836749c9
5 changed files with 12 additions and 0 deletions
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4
include/linux/bpf-cgroup.h
View File

@ -210,6 +210,9 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) \
BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET_SOCK_CREATE)
#define BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk) \
BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET_SOCK_RELEASE)
#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) \
BPF_CGROUP_RUN_SK_PROG(sk, BPF_CGROUP_INET4_POST_BIND)
@ -401,6 +404,7 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map,
#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; })
#define BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET6_BIND(sk, uaddr) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) ({ 0; })

1
include/uapi/linux/bpf.h
View File

@ -226,6 +226,7 @@ enum bpf_attach_type {
BPF_CGROUP_INET4_GETSOCKNAME,
BPF_CGROUP_INET6_GETSOCKNAME,
BPF_XDP_DEVMAP,
BPF_CGROUP_INET_SOCK_RELEASE,
__MAX_BPF_ATTACH_TYPE
};

3
kernel/bpf/syscall.c
View File

@ -1981,6 +1981,7 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
case BPF_PROG_TYPE_CGROUP_SOCK:
switch (expected_attach_type) {
case BPF_CGROUP_INET_SOCK_CREATE:
case BPF_CGROUP_INET_SOCK_RELEASE:
case BPF_CGROUP_INET4_POST_BIND:
case BPF_CGROUP_INET6_POST_BIND:
return 0;
@ -2779,6 +2780,7 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type)
return BPF_PROG_TYPE_CGROUP_SKB;
break;
case BPF_CGROUP_INET_SOCK_CREATE:
case BPF_CGROUP_INET_SOCK_RELEASE:
case BPF_CGROUP_INET4_POST_BIND:
case BPF_CGROUP_INET6_POST_BIND:
return BPF_PROG_TYPE_CGROUP_SOCK;
@ -2929,6 +2931,7 @@ static int bpf_prog_query(const union bpf_attr *attr,
case BPF_CGROUP_INET_INGRESS:
case BPF_CGROUP_INET_EGRESS:
case BPF_CGROUP_INET_SOCK_CREATE:
case BPF_CGROUP_INET_SOCK_RELEASE:
case BPF_CGROUP_INET4_BIND:
case BPF_CGROUP_INET6_BIND:
case BPF_CGROUP_INET4_POST_BIND:

1
net/core/filter.c
View File

@ -6890,6 +6890,7 @@ static bool __sock_filter_check_attach_type(int off,
case offsetof(struct bpf_sock, priority):
switch (attach_type) {
case BPF_CGROUP_INET_SOCK_CREATE:
case BPF_CGROUP_INET_SOCK_RELEASE:
goto full_access;
default:
return false;

3
net/ipv4/af_inet.c
View File

@ -411,6 +411,9 @@ int inet_release(struct socket *sock)
if (sk) {
long timeout;
if (!sk->sk_kern_sock)
BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk);
/* Applications forget to leave groups before exiting */
ip_mc_drop_socket(sk);