The new helper bpf_tcp_raw_gen_tscookie allows an XDP program to
generate timestamp cookies (to be used together with SYN cookies) which
encode different options set by the client in the SYN packet: SACK
support, ECN support, window scale. These options are encoded in lower
bits of the timestamp, which will be returned by the client in a
subsequent ACK packet. The format is the same used by synproxy.
Signed-off-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxx>
Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
---
include/net/tcp.h | 1 +
include/uapi/linux/bpf.h | 27 +++++++++++++++
net/core/filter.c | 38 +++++++++++++++++++++
net/ipv4/syncookies.c | 60 ++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 27 +++++++++++++++
5 files changed, 153 insertions(+)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1cc96a225848..651820bef6a2 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -564,6 +564,7 @@ u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
u16 *mssp);
__u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
u64 cookie_init_timestamp(struct request_sock *req, u64 now);
+bool cookie_init_timestamp_raw(struct tcphdr *th, __be32 *tsval, __be32 *tsecr);
bool cookie_timestamp_decode(const struct net *net,
struct tcp_options_received *opt);
bool cookie_ecn_ok(const struct tcp_options_received *opt,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e32f72077250..791790b41874 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5053,6 +5053,32 @@ union bpf_attr {
*
* **-EPROTONOSUPPORT** if the IP version is not 4 or 6 (or 6, but
* CONFIG_IPV6 is disabled).
+ *
+ * int bpf_tcp_raw_gen_tscookie(struct tcphdr *th, u32 th_len, __be32 *tsopt, u32 tsopt_len)
+ * Description
+ * Try to generate a timestamp cookie which encodes some of the
+ * flags sent by the client in the SYN packet: SACK support, ECN
+ * support, window scale. To be used with SYN cookies.
+ *
+ * *th* points to the start of the TCP header of the client's SYN
+ * packet, while *th_len* contains the length of the TCP header (at
+ * least **sizeof**\ (**struct tcphdr**)).
+ *
+ * *tsopt* points to the output location where to put the resulting
+ * timestamp values: tsval and tsecr, in the format of the TCP
+ * timestamp option.
+ *
+ * Return
+ * On success, 0.
+ *
+ * On failure, the returned value is one of the following:
+ *
+ * **-EINVAL** if the input arguments are invalid.
+ *
+ * **-ENOENT** if the TCP header doesn't have the timestamp option.
+ *
+ * **-EOPNOTSUPP** if the kernel configuration does not enable SYN
+ * cookies (CONFIG_SYN_COOKIES is off).
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5238,6 +5264,7 @@ union bpf_attr {
FN(ct_release), \
FN(tcp_raw_gen_syncookie), \
FN(tcp_raw_check_syncookie), \
+ FN(tcp_raw_gen_tscookie), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/net/core/filter.c b/net/core/filter.c
index 5f03d4a282a0..73fe20ef7442 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7403,6 +7403,42 @@ static const struct bpf_func_proto bpf_tcp_raw_check_syncookie_proto = {
.arg4_type = ARG_CONST_SIZE,
};
+BPF_CALL_4(bpf_tcp_raw_gen_tscookie, struct tcphdr *, th, u32, th_len,
+ __be32 *, tsopt, u32, tsopt_len)
+{
+ int err;
+
+#ifdef CONFIG_SYN_COOKIES
+ if (tsopt_len != sizeof(u64)) {
+ err = -EINVAL;
+ goto err_out;
+ }
+
+ if (!cookie_init_timestamp_raw(th, &tsopt[0], &tsopt[1])) {
+ err = -ENOENT;
+ goto err_out;
+ }
+
+ return 0;
+err_out:
+#else
+ err = -EOPNOTSUPP;
+#endif
+ memset(tsopt, 0, tsopt_len);
+ return err;
+}
+
+static const struct bpf_func_proto bpf_tcp_raw_gen_tscookie_proto = {
+ .func = bpf_tcp_raw_gen_tscookie,
+ .gpl_only = false,
+ .pkt_access = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+ .arg3_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg4_type = ARG_CONST_SIZE,
+};
+
#endif /* CONFIG_INET */
bool bpf_helper_changes_pkt_data(void *func)
@@ -7825,6 +7861,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_tcp_raw_gen_syncookie_proto;
case BPF_FUNC_tcp_raw_check_syncookie:
return &bpf_tcp_raw_check_syncookie_proto;
+ case BPF_FUNC_tcp_raw_gen_tscookie:
+ return &bpf_tcp_raw_gen_tscookie_proto;
#endif
default:
return bpf_sk_base_func_proto(func_id);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 8696dc343ad2..4dd2c7a096eb 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -85,6 +85,66 @@ u64 cookie_init_timestamp(struct request_sock *req, u64 now)
return (u64)ts * (NSEC_PER_SEC / TCP_TS_HZ);
}
+bool cookie_init_timestamp_raw(struct tcphdr *th, __be32 *tsval, __be32 *tsecr)
+{
+ int length = (th->doff * 4) - sizeof(*th);
+ u8 wscale = TS_OPT_WSCALE_MASK;
+ bool option_timestamp = false;
+ bool option_sack = false;
+ u32 cookie;
+ u8 *ptr;
+
+ ptr = (u8 *)(th + 1);
+
+ while (length > 0) {
+ u8 opcode = *ptr++;
+ u8 opsize;
+
+ if (opcode == TCPOPT_EOL)
+ break;
+ if (opcode == TCPOPT_NOP) {
+ length--;
+ continue;
+ }
+
+ if (length < 2)
+ break;
+ opsize = *ptr++;
+ if (opsize < 2)
+ break;
+ if (opsize > length)
+ break;
+
+ switch (opcode) {
+ case TCPOPT_WINDOW:
