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bpf: tcp: Handle BPF SYN Cookie in cookie_v[46]_check().

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We will support arbitrary SYN Cookie with BPF in the following
patch.

If BPF prog validates ACK and kfunc allocates a reqsk, it will
be carried to cookie_[46]_check() as skb->sk.  If skb->sk is not
NULL, we call cookie_bpf_check().

Then, we clear skb->sk and skb->destructor, which are needed not
to hold refcnt for reqsk and the listener.  See the following patch
for details.

After that, we finish initialisation for the remaining fields with
cookie_tcp_reqsk_init().

Note that the server side WScale is set only for non-BPF SYN Cookie.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240115205514.68364-5-kuniyu@amazon.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2024-01-15 12:55:12 -08:00 committed by Alexei Starovoitov
parent 8b5ac68fb5
commit 695751e31a
3 changed files with 56 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
include/net/tcp.h
View File

@ -599,6 +599,26 @@ static inline bool cookie_ecn_ok(const struct net *net, const struct dst_entry *
dst_feature(dst, RTAX_FEATURE_ECN);
}
#if IS_ENABLED(CONFIG_BPF)
static inline bool cookie_bpf_ok(struct sk_buff *skb)
{
return skb->sk;
}
struct request_sock *cookie_bpf_check(struct sock *sk, struct sk_buff *skb);
#else
static inline bool cookie_bpf_ok(struct sk_buff *skb)
{
return false;
}
static inline struct request_sock *cookie_bpf_check(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
return NULL;
}
#endif
/* From net/ipv6/syncookies.c */
int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th);
struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);

31
net/ipv4/syncookies.c
View File

@ -295,6 +295,24 @@ static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
return 0;
}
#if IS_ENABLED(CONFIG_BPF)
struct request_sock *cookie_bpf_check(struct sock *sk, struct sk_buff *skb)
{
struct request_sock *req = inet_reqsk(skb->sk);
skb->sk = NULL;
skb->destructor = NULL;
if (cookie_tcp_reqsk_init(sk, skb, req)) {
reqsk_free(req);
req = NULL;
}
return req;
}
EXPORT_SYMBOL_GPL(cookie_bpf_check);
#endif
struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
struct sock *sk, struct sk_buff *skb,
struct tcp_options_received *tcp_opt,
@ -395,9 +413,13 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
!th->ack || th->rst)
goto out;
req = cookie_tcp_check(net, sk, skb);
if (IS_ERR(req))
goto out;
if (cookie_bpf_ok(skb)) {
req = cookie_bpf_check(sk, skb);
} else {
req = cookie_tcp_check(net, sk, skb);
if (IS_ERR(req))
goto out;
}
if (!req)
goto out_drop;
@ -445,7 +467,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
ireq->wscale_ok, &rcv_wscale,
dst_metric(&rt->dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;
if (!req->syncookie)
ireq->rcv_wscale = rcv_wscale;
ireq->ecn_ok &= cookie_ecn_ok(net, &rt->dst);
ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);

13
net/ipv6/syncookies.c
View File

@ -182,9 +182,13 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
!th->ack || th->rst)
goto out;
req = cookie_tcp_check(net, sk, skb);
if (IS_ERR(req))
goto out;
if (cookie_bpf_ok(skb)) {
req = cookie_bpf_check(sk, skb);
} else {
req = cookie_tcp_check(net, sk, skb);
if (IS_ERR(req))
goto out;
}
if (!req)
goto out_drop;
@ -247,7 +251,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
ireq->wscale_ok, &rcv_wscale,
dst_metric(dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;
if (!req->syncookie)
ireq->rcv_wscale = rcv_wscale;
ireq->ecn_ok &= cookie_ecn_ok(net, dst);
ret = tcp_get_cookie_sock(sk, skb, req, dst);