bpf: add bpf_tcp_gen_syncookie helper (70d66244) · Commits · 戴 / test

include/uapi/linux/bpf.h

+29 −1

Original line number	Diff line number	Diff line
		@@ -2714,6 +2714,33 @@ union bpf_attr {
		* -EPERM if no permission to send the sig.
		*
		* -EAGAIN if bpf program can try again.
		*
		* s64 bpf_tcp_gen_syncookie(struct bpf_sock sk, void iph, u32 iph_len, struct tcphdr *th, u32 th_len)
		* Description
		* Try to issue a SYN cookie for the packet with corresponding
		* IP/TCP headers, iph and th, on the listening socket in sk.
		*
		* iph points to the start of the IPv4 or IPv6 header, while
		* iph_len contains sizeof\ (struct iphdr) or
		* sizeof\ (struct ip6hdr).
		*
		* th points to the start of the TCP header, while th_len
		* contains the length of the TCP header.
		*
		* Return
		* On success, lower 32 bits hold the generated SYN cookie in
		* followed by 16 bits which hold the MSS value for that cookie,
		* and the top 16 bits are unused.
		*
		* On failure, the returned value is one of the following:
		*
		* -EINVAL SYN cookie cannot be issued due to error
		*
		* -ENOENT SYN cookie should not be issued (no SYN flood)
		*
		* -EOPNOTSUPP kernel configuration does not enable SYN cookies
		*
		* -EPROTONOSUPPORT IP packet version is not 4 or 6
		*/
		#define __BPF_FUNC_MAPPER(FN) \
		FN(unspec), \
		@@ -2825,7 +2852,8 @@ union bpf_attr {
		FN(strtoul), \
		FN(sk_storage_get), \
		FN(sk_storage_delete), \
		FN(send_signal),
		FN(send_signal), \
		FN(tcp_gen_syncookie),

		/* integer value in 'imm' field of BPF_CALL instruction selects which helper
		* function eBPF program intends to call

net/core/filter.c

+73 −0

Original line number	Diff line number	Diff line
		@@ -5855,6 +5855,75 @@ static const struct bpf_func_proto bpf_tcp_check_syncookie_proto = {
		.arg5_type = ARG_CONST_SIZE,
		};

		BPF_CALL_5(bpf_tcp_gen_syncookie, struct sock , sk, void , iph, u32, iph_len,
		struct tcphdr *, th, u32, th_len)
		{
		#ifdef CONFIG_SYN_COOKIES
		u32 cookie;
		u16 mss;

		if (unlikely(th_len < sizeof(th) \|\| th_len != th->doff 4))
		return -EINVAL;

		if (sk->sk_protocol != IPPROTO_TCP \|\| sk->sk_state != TCP_LISTEN)
		return -EINVAL;

		if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies)
		return -ENOENT;

		if (!th->syn \|\| th->ack \|\| th->fin \|\| th->rst)
		return -EINVAL;

		if (unlikely(iph_len < sizeof(struct iphdr)))
		return -EINVAL;

		/* Both struct iphdr and struct ipv6hdr have the version field at the
		* same offset so we can cast to the shorter header (struct iphdr).
		*/
		switch (((struct iphdr *)iph)->version) {
		case 4:
		if (sk->sk_family == AF_INET6 && sk->sk_ipv6only)
		return -EINVAL;

		mss = tcp_v4_get_syncookie(sk, iph, th, &cookie);
		break;

		#if IS_BUILTIN(CONFIG_IPV6)
		case 6:
		if (unlikely(iph_len < sizeof(struct ipv6hdr)))
		return -EINVAL;

		if (sk->sk_family != AF_INET6)
		return -EINVAL;

		mss = tcp_v6_get_syncookie(sk, iph, th, &cookie);
		break;
		#endif /* CONFIG_IPV6 */

		default:
		return -EPROTONOSUPPORT;
		}
		if (mss <= 0)
		return -ENOENT;

		return cookie \| ((u64)mss << 32);
		#else
		return -EOPNOTSUPP;
		#endif /* CONFIG_SYN_COOKIES */
		}

		static const struct bpf_func_proto bpf_tcp_gen_syncookie_proto = {
		.func = bpf_tcp_gen_syncookie,
		.gpl_only = true, /* __cookie_v_init_sequence() is GPL /
		.pkt_access = true,
		.ret_type = RET_INTEGER,
		.arg1_type = ARG_PTR_TO_SOCK_COMMON,
		.arg2_type = ARG_PTR_TO_MEM,
		.arg3_type = ARG_CONST_SIZE,
		.arg4_type = ARG_PTR_TO_MEM,
		.arg5_type = ARG_CONST_SIZE,
		};

		#endif /* CONFIG_INET */

		bool bpf_helper_changes_pkt_data(void *func)
		@@ -6144,6 +6213,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
		return &bpf_tcp_check_syncookie_proto;
		case BPF_FUNC_skb_ecn_set_ce:
		return &bpf_skb_ecn_set_ce_proto;
		case BPF_FUNC_tcp_gen_syncookie:
		return &bpf_tcp_gen_syncookie_proto;
		#endif
		default:
		return bpf_base_func_proto(func_id);
		@@ -6183,6 +6254,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
		return &bpf_xdp_skc_lookup_tcp_proto;
		case BPF_FUNC_tcp_check_syncookie:
		return &bpf_tcp_check_syncookie_proto;
		case BPF_FUNC_tcp_gen_syncookie:
		return &bpf_tcp_gen_syncookie_proto;
		#endif
		default:
		return bpf_base_func_proto(func_id);

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