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