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. 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@xxxxxxxxxx> --- include/net/tcp.h | 20 ++++++++++++++++++++ net/ipv4/syncookies.c | 31 +++++++++++++++++++++++++++---- net/ipv6/syncookies.c | 13 +++++++++---- 3 files changed, 56 insertions(+), 8 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index c77354d1b86d..b5d7149eb0f8 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -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); diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 981944c22820..be88bf586ff9 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -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); diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index c8d2ca27220c..6b9c69278819 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -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); -- 2.30.2