Commit b13d8807 authored by Lawrence Brakmo's avatar Lawrence Brakmo Committed by Alexei Starovoitov

bpf: Adds field bpf_sock_ops_cb_flags to tcp_sock

Adds field bpf_sock_ops_cb_flags to tcp_sock and bpf_sock_ops. Its primary
use is to determine if there should be calls to sock_ops bpf program at
various points in the TCP code. The field is initialized to zero,
disabling the calls. A sock_ops BPF program can set it, per connection and
as necessary, when the connection is established.

It also adds support for reading and writting the field within a
sock_ops BPF program. Reading is done by accessing the field directly.
However, writing is done through the helper function
bpf_sock_ops_cb_flags_set, in order to return an error if a BPF program
is trying to set a callback that is not supported in the current kernel
(i.e. running an older kernel). The helper function returns 0 if it was
able to set all of the bits set in the argument, a positive number
containing the bits that could not be set, or -EINVAL if the socket is
not a full TCP socket.

Examples of where one could call the bpf program:

1) When RTO fires
2) When a packet is retransmitted
3) When the connection terminates
4) When a packet is sent
5) When a packet is received
Signed-off-by: default avatarLawrence Brakmo <brakmo@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent de525be2
......@@ -335,6 +335,17 @@ struct tcp_sock {
int linger2;
/* Sock_ops bpf program related variables */
#ifdef CONFIG_BPF
u8 bpf_sock_ops_cb_flags; /* Control calling BPF programs
* values defined in uapi/linux/tcp.h
*/
#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_cb_flags & ARG)
#else
#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
#endif
/* Receiver side RTT estimation */
struct {
u32 rtt_us;
......
......@@ -642,6 +642,14 @@ union bpf_attr {
* @optlen: length of optval in bytes
* Return: 0 or negative error
*
* int bpf_sock_ops_cb_flags_set(bpf_sock_ops, flags)
* Set callback flags for sock_ops
* @bpf_sock_ops: pointer to bpf_sock_ops_kern struct
* @flags: flags value
* Return: 0 for no error
* -EINVAL if there is no full tcp socket
* bits in flags that are not supported by current kernel
*
* int bpf_skb_adjust_room(skb, len_diff, mode, flags)
* Grow or shrink room in sk_buff.
* @skb: pointer to skb
......@@ -748,7 +756,8 @@ union bpf_attr {
FN(perf_event_read_value), \
FN(perf_prog_read_value), \
FN(getsockopt), \
FN(override_return),
FN(override_return), \
FN(sock_ops_cb_flags_set),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
......@@ -969,8 +978,14 @@ struct bpf_sock_ops {
*/
__u32 snd_cwnd;
__u32 srtt_us; /* Averaged RTT << 3 in usecs */
__u32 bpf_sock_ops_cb_flags; /* flags defined in uapi/linux/tcp.h */
};
/* Definitions for bpf_sock_ops_cb_flags */
#define BPF_SOCK_OPS_ALL_CB_FLAGS 0 /* Mask of all currently
* supported cb flags
*/
/* List of known BPF sock_ops operators.
* New entries can only be added at the end
*/
......
......@@ -3328,6 +3328,33 @@ static const struct bpf_func_proto bpf_getsockopt_proto = {
.arg5_type = ARG_CONST_SIZE,
};
BPF_CALL_2(bpf_sock_ops_cb_flags_set, struct bpf_sock_ops_kern *, bpf_sock,
int, argval)
{
struct sock *sk = bpf_sock->sk;
int val = argval & BPF_SOCK_OPS_ALL_CB_FLAGS;
if (!sk_fullsock(sk))
return -EINVAL;
#ifdef CONFIG_INET
if (val)
tcp_sk(sk)->bpf_sock_ops_cb_flags = val;
return argval & (~BPF_SOCK_OPS_ALL_CB_FLAGS);
#else
return -EINVAL;
#endif
}
static const struct bpf_func_proto bpf_sock_ops_cb_flags_set_proto = {
.func = bpf_sock_ops_cb_flags_set,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
};
static const struct bpf_func_proto *
bpf_base_func_proto(enum bpf_func_id func_id)
{
......@@ -3510,6 +3537,8 @@ static const struct bpf_func_proto *
return &bpf_setsockopt_proto;
case BPF_FUNC_getsockopt:
return &bpf_getsockopt_proto;
case BPF_FUNC_sock_ops_cb_flags_set:
return &bpf_sock_ops_cb_flags_set_proto;
case BPF_FUNC_sock_map_update:
return &bpf_sock_map_update_proto;
default:
......@@ -4546,6 +4575,11 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
case offsetof(struct bpf_sock_ops, srtt_us):
SOCK_OPS_GET_FIELD(srtt_us, srtt_us, struct tcp_sock);
break;
case offsetof(struct bpf_sock_ops, bpf_sock_ops_cb_flags):
SOCK_OPS_GET_FIELD(bpf_sock_ops_cb_flags, bpf_sock_ops_cb_flags,
struct tcp_sock);
break;
}
return insn - insn_buf;
}
......
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