From: Petar Penkov <ppenkov.kernel@gmail.com>
To: netdev@vger.kernel.org, bpf@vger.kernel.org
Cc: davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net,
edumazet@google.com, lmb@cloudflare.com, sdf@google.com,
Petar Penkov <ppenkov@google.com>
Subject: [bpf-next RFC 3/6] bpf: add bpf_tcp_gen_syncookie helper
Date: Mon, 15 Jul 2019 17:26:47 -0700 [thread overview]
Message-ID: <20190716002650.154729-4-ppenkov.kernel@gmail.com> (raw)
In-Reply-To: <20190716002650.154729-1-ppenkov.kernel@gmail.com>
From: Petar Penkov <ppenkov@google.com>
This helper function allows BPF programs to try to generate SYN
cookies, given a reference to a listener socket. The function works
from XDP and with an skb context since bpf_skc_lookup_tcp can lookup a
socket in both cases.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
---
include/uapi/linux/bpf.h | 30 ++++++++++++++++++-
net/core/filter.c | 62 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 91 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6f68438aa4ed..abf4a85c76d1 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2713,6 +2713,33 @@ 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 **sizeof**\ (**struct tcphdr**).
+ *
+ * Return
+ * On success, lower 32 bits hold the generated SYN cookie in
+ * network order and the higher 32 bits hold the MSS value for that
+ * cookie.
+ *
+ * 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)
+ *
+ * **-ENOTSUPP** kernel configuration does not enable SYN cookies
+ *
+ * **-EPROTONOSUPPORT** *sk* family is not AF_INET/AF_INET6
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2824,7 +2851,8 @@ 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
diff --git a/net/core/filter.c b/net/core/filter.c
index 47f6386fb17a..109fd1e286f4 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5850,6 +5850,64 @@ 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)))
+ return -EINVAL;
+
+ if (sk->sk_protocol != IPPROTO_TCP || sk->sk_state != TCP_LISTEN)
+ return -EINVAL;
+
+ if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies)
+ return -EINVAL;
+
+ if (!th->syn || th->ack || th->fin || th->rst)
+ return -EINVAL;
+
+ switch (sk->sk_family) {
+ case AF_INET:
+ if (unlikely(iph_len < sizeof(struct iphdr)))
+ return -EINVAL;
+ mss = tcp_v4_get_syncookie(sk, iph, th, &cookie);
+ break;
+
+#if IS_BUILTIN(CONFIG_IPV6)
+ case AF_INET6:
+ if (unlikely(iph_len < sizeof(struct ipv6hdr)))
+ return -EINVAL;
+ mss = tcp_v6_get_syncookie(sk, iph, th, &cookie);
+ break;
+#endif /* CONFIG_IPV6 */
+
+ default:
+ return -EPROTONOSUPPORT;
+ }
+ if (mss <= 0)
+ return -ENOENT;
+
+ return htonl(cookie) | ((u64)mss << 32);
+#else
+ return -ENOTSUPP;
+#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)
@@ -6135,6 +6193,8 @@ 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);
@@ -6174,6 +6234,8 @@ 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);
--
2.22.0.510.g264f2c817a-goog
next prev parent reply other threads:[~2019-07-16 0:27 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-16 0:26 [bpf-next RFC 0/6] Introduce a BPF helper to generate SYN cookies Petar Penkov
2019-07-16 0:26 ` [bpf-next RFC 1/6] tcp: tcp_syn_flood_action read port from socket Petar Penkov
2019-07-16 0:26 ` [bpf-next RFC 2/6] tcp: add skb-less helpers to retrieve SYN cookie Petar Penkov
2019-07-16 11:34 ` Lorenz Bauer
2019-07-17 0:23 ` Petar Penkov
2019-07-16 0:26 ` Petar Penkov [this message]
2019-07-16 7:59 ` [bpf-next RFC 3/6] bpf: add bpf_tcp_gen_syncookie helper Eric Dumazet
2019-07-16 11:56 ` Lorenz Bauer
2019-07-17 0:27 ` Petar Penkov
2019-07-17 2:26 ` Alexei Starovoitov
2019-07-17 3:33 ` Petar Penkov
2019-07-16 11:54 ` Lorenz Bauer
2019-07-16 0:26 ` [bpf-next RFC 4/6] bpf: sync bpf.h to tools/ Petar Penkov
2019-07-16 0:26 ` [bpf-next RFC 5/6] selftests/bpf: bpf_tcp_gen_syncookie->bpf_helpers Petar Penkov
2019-07-16 0:26 ` [bpf-next RFC 6/6] selftests/bpf: add test for bpf_tcp_gen_syncookie Petar Penkov
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