diff options
author | Kuniyuki Iwashima <kuniyu@amazon.com> | 2024-01-15 23:55:13 +0300 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2024-01-24 01:40:24 +0300 |
commit | e472f88891abbc535a5e16a68a104073985f6061 (patch) | |
tree | bf5fa7d7e631cb74d6bc29759fd1cfefc7927d3b /include/net/tcp.h | |
parent | 695751e31a63efd2bbe6779873adf1e4deb00cd5 (diff) | |
download | linux-e472f88891abbc535a5e16a68a104073985f6061.tar.xz |
bpf: tcp: Support arbitrary SYN Cookie.
This patch adds a new kfunc available at TC hook to support arbitrary
SYN Cookie.
The basic usage is as follows:
struct bpf_tcp_req_attrs attrs = {
.mss = mss,
.wscale_ok = wscale_ok,
.rcv_wscale = rcv_wscale, /* Server's WScale < 15 */
.snd_wscale = snd_wscale, /* Client's WScale < 15 */
.tstamp_ok = tstamp_ok,
.rcv_tsval = tsval,
.rcv_tsecr = tsecr, /* Server's Initial TSval */
.usec_ts_ok = usec_ts_ok,
.sack_ok = sack_ok,
.ecn_ok = ecn_ok,
}
skc = bpf_skc_lookup_tcp(...);
sk = (struct sock *)bpf_skc_to_tcp_sock(skc);
bpf_sk_assign_tcp_reqsk(skb, sk, attrs, sizeof(attrs));
bpf_sk_release(skc);
bpf_sk_assign_tcp_reqsk() takes skb, a listener sk, and struct
bpf_tcp_req_attrs and allocates reqsk and configures it. Then,
bpf_sk_assign_tcp_reqsk() links reqsk with skb and the listener.
The notable thing here is that we do not hold refcnt for both reqsk
and listener. To differentiate that, we mark reqsk->syncookie, which
is only used in TX for now. So, if reqsk->syncookie is 1 in RX, it
means that the reqsk is allocated by kfunc.
When skb is freed, sock_pfree() checks if reqsk->syncookie is 1,
and in that case, we set NULL to reqsk->rsk_listener before calling
reqsk_free() as reqsk does not hold a refcnt of the listener.
When the TCP stack looks up a socket from the skb, we steal the
listener from the reqsk in skb_steal_sock() and create a full sk
in cookie_v[46]_check().
The refcnt of reqsk will finally be set to 1 in tcp_get_cookie_sock()
after creating a full sk.
Note that we can extend struct bpf_tcp_req_attrs in the future when
we add a new attribute that is determined in 3WHS.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240115205514.68364-6-kuniyu@amazon.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include/net/tcp.h')
-rw-r--r-- | include/net/tcp.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index dfe99a084a71..451dc1373970 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -600,6 +600,20 @@ static inline bool cookie_ecn_ok(const struct net *net, const struct dst_entry * } #if IS_ENABLED(CONFIG_BPF) +struct bpf_tcp_req_attrs { + u32 rcv_tsval; + u32 rcv_tsecr; + u16 mss; + u8 rcv_wscale; + u8 snd_wscale; + u8 ecn_ok; + u8 wscale_ok; + u8 sack_ok; + u8 tstamp_ok; + u8 usec_ts_ok; + u8 reserved[3]; +}; + static inline bool cookie_bpf_ok(struct sk_buff *skb) { return skb->sk; |