tcp: Factorise cookie-dependent fields initialisation in cookie_v[46]_check()

We will support arbitrary SYN Cookie with BPF, and then kfunc at
TC will preallocate reqsk and initialise some fields that should
not be overwritten later by cookie_v[46]_check().

To simplify the flow in cookie_v[46]_check(), we move such fields'
initialisation to cookie_tcp_reqsk_alloc() and factorise non-BPF
SYN Cookie handling into cookie_tcp_check(), where we validate the
cookie and allocate reqsk, as done by kfunc later.

Note that we set ireq->ecn_ok in two steps, the latter of which will
be shared by the BPF case.  As cookie_ecn_ok() is one-liner, now
it's inlined.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231129022924.96156-9-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index d4d0e97..973555c 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -494,7 +494,10 @@ struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th);
 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
-                                           struct sock *sk, struct sk_buff *skb);
+                                           struct sock *sk, struct sk_buff *skb,
+                                           struct tcp_options_received *tcp_opt,
+                                           int mss, u32 tsoff);
+
 #ifdef CONFIG_SYN_COOKIES
 
 /* Syncookies use a monotonic timer which increments every 60 seconds.
@@ -580,8 +583,12 @@ __u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
 u64 cookie_init_timestamp(struct request_sock *req, u64 now);
 bool cookie_timestamp_decode(const struct net *net,
                             struct tcp_options_received *opt);
-bool cookie_ecn_ok(const struct tcp_options_received *opt,
-                  const struct net *net, const struct dst_entry *dst);
+
+static inline bool cookie_ecn_ok(const struct net *net, const struct dst_entry *dst)
+{
+       return READ_ONCE(net->ipv4.sysctl_tcp_ecn) ||
+               dst_feature(dst, RTAX_FEATURE_ECN);
+}
 
 /* From net/ipv6/syncookies.c */
 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th);

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index f4bcd48..61f1c96 100644 (file)
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -270,21 +270,6 @@ bool cookie_timestamp_decode(const struct net *net,
 }
 EXPORT_SYMBOL(cookie_timestamp_decode);
 
-bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
-                  const struct net *net, const struct dst_entry *dst)
-{
-       bool ecn_ok = tcp_opt->rcv_tsecr & TS_OPT_ECN;
-
-       if (!ecn_ok)
-               return false;
-
-       if (READ_ONCE(net->ipv4.sysctl_tcp_ecn))
-               return true;
-
-       return dst_feature(dst, RTAX_FEATURE_ECN);
-}
-EXPORT_SYMBOL(cookie_ecn_ok);
-
 static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
                                 struct request_sock *req)
 {
@@ -320,8 +305,12 @@ static int cookie_tcp_reqsk_init(struct sock *sk, struct sk_buff *skb,
 }
 
 struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
-                                           struct sock *sk, struct sk_buff *skb)
+                                           struct sock *sk, struct sk_buff *skb,
+                                           struct tcp_options_received *tcp_opt,
+                                           int mss, u32 tsoff)
 {
+       struct inet_request_sock *ireq;
+       struct tcp_request_sock *treq;
        struct request_sock *req;
 
        if (sk_is_mptcp(sk))
@@ -337,40 +326,36 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
                return NULL;
        }
 
+       ireq = inet_rsk(req);
+       treq = tcp_rsk(req);
+
+       req->mss = mss;
+       req->ts_recent = tcp_opt->saw_tstamp ? tcp_opt->rcv_tsval : 0;
+
+       ireq->snd_wscale = tcp_opt->snd_wscale;
+       ireq->tstamp_ok = tcp_opt->saw_tstamp;
+       ireq->sack_ok = tcp_opt->sack_ok;
+       ireq->wscale_ok = tcp_opt->wscale_ok;
+       ireq->ecn_ok = !!(tcp_opt->rcv_tsecr & TS_OPT_ECN);
+
+       treq->ts_off = tsoff;
+
        return req;
 }
 EXPORT_SYMBOL_GPL(cookie_tcp_reqsk_alloc);
 
-/* On input, sk is a listener.
- * Output is listener if incoming packet would not create a child
- *           NULL if memory could not be allocated.
- */
-struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
+static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
+                                            struct sk_buff *skb)
 {
-       struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
-       const struct tcphdr *th = tcp_hdr(skb);
        struct tcp_options_received tcp_opt;
-       struct tcp_sock *tp = tcp_sk(sk);
-       struct inet_request_sock *ireq;
-       struct net *net = sock_net(sk);
-       struct tcp_request_sock *treq;
-       struct request_sock *req;
-       struct sock *ret = sk;
-       int full_space, mss;
-       struct flowi4 fl4;
-       struct rtable *rt;
-       __u8 rcv_wscale;
        u32 tsoff = 0;
-
-       if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
-           !th->ack || th->rst)
-               goto out;
+       int mss;
 
        if (tcp_synq_no_recent_overflow(sk))
                goto out;
 
-       mss = __cookie_v4_check(ip_hdr(skb), th);
-       if (mss == 0) {
+       mss = __cookie_v4_check(ip_hdr(skb), tcp_hdr(skb));
+       if (!mss) {
                __NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
                goto out;
        }
@@ -391,21 +376,44 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
        if (!cookie_timestamp_decode(net, &tcp_opt))
                goto out;
 
-       req = cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb);
+       return cookie_tcp_reqsk_alloc(&tcp_request_sock_ops, sk, skb,
+                                     &tcp_opt, mss, tsoff);
+out:
+       return ERR_PTR(-EINVAL);
+}
+
+/* On input, sk is a listener.
+ * Output is listener if incoming packet would not create a child
+ *           NULL if memory could not be allocated.
+ */
+struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
+{
+       struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
+       const struct tcphdr *th = tcp_hdr(skb);
+       struct tcp_sock *tp = tcp_sk(sk);
+       struct inet_request_sock *ireq;
+       struct net *net = sock_net(sk);
+       struct request_sock *req;
+       struct sock *ret = sk;
+       struct flowi4 fl4;
+       struct rtable *rt;
+       __u8 rcv_wscale;
+       int full_space;
+
+       if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
+           !th->ack || th->rst)
+               goto out;
+
+       req = cookie_tcp_check(net, sk, skb);
+       if (IS_ERR(req))
+               goto out;
        if (!req)
                goto out_drop;
 
        ireq = inet_rsk(req);
-       treq = tcp_rsk(req);
-       treq->ts_off            = tsoff;
-       req->mss                = mss;
+
        sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
        sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
-       ireq->snd_wscale        = tcp_opt.snd_wscale;
-       ireq->sack_ok           = tcp_opt.sack_ok;
-       ireq->wscale_ok         = tcp_opt.wscale_ok;
-       ireq->tstamp_ok         = tcp_opt.saw_tstamp;
-       req->ts_recent          = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
 
        /* We throwed the options of the initial SYN away, so we hope
         * the ACK carries the same options again (see RFC1122 4.2.3.8)
@@ -447,7 +455,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
                                  dst_metric(&rt->dst, RTAX_INITRWND));
 
        ireq->rcv_wscale  = rcv_wscale;
-       ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, &rt->dst);
+       ireq->ecn_ok &= cookie_ecn_ok(net, &rt->dst);
 
        ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst);
        /* ip_queue_xmit() depends on our flow being setup

diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index e0a9220..c8d2ca2 100644 (file)
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -127,31 +127,18 @@ int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th)
 }
 EXPORT_SYMBOL_GPL(__cookie_v6_check);
 
-struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
+static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk,
+                                            struct sk_buff *skb)
 {
-       const struct tcphdr *th = tcp_hdr(skb);
-       struct ipv6_pinfo *np = inet6_sk(sk);
        struct tcp_options_received tcp_opt;
-       struct tcp_sock *tp = tcp_sk(sk);
-       struct inet_request_sock *ireq;
-       struct net *net = sock_net(sk);
-       struct tcp_request_sock *treq;
-       struct request_sock *req;
-       struct dst_entry *dst;
-       struct sock *ret = sk;
-       int full_space, mss;
-       __u8 rcv_wscale;
        u32 tsoff = 0;
-
-       if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
-           !th->ack || th->rst)
-               goto out;
+       int mss;
 
        if (tcp_synq_no_recent_overflow(sk))
                goto out;
 
-       mss = __cookie_v6_check(ipv6_hdr(skb), th);
-       if (mss == 0) {
+       mss = __cookie_v6_check(ipv6_hdr(skb), tcp_hdr(skb));
+       if (!mss) {
                __NET_INC_STATS(net, LINUX_MIB_SYNCOOKIESFAILED);
                goto out;
        }
@@ -172,14 +159,37 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
        if (!cookie_timestamp_decode(net, &tcp_opt))
                goto out;
 
-       req = cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb);
+       return cookie_tcp_reqsk_alloc(&tcp6_request_sock_ops, sk, skb,
+                                     &tcp_opt, mss, tsoff);
+out:
+       return ERR_PTR(-EINVAL);
+}
+
+struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
+{
+       const struct tcphdr *th = tcp_hdr(skb);
+       struct ipv6_pinfo *np = inet6_sk(sk);
+       struct tcp_sock *tp = tcp_sk(sk);
+       struct inet_request_sock *ireq;
+       struct net *net = sock_net(sk);
+       struct request_sock *req;
+       struct dst_entry *dst;
+       struct sock *ret = sk;
+       __u8 rcv_wscale;
+       int full_space;
+
+       if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
+           !th->ack || th->rst)
+               goto out;
+
+       req = cookie_tcp_check(net, sk, skb);
+       if (IS_ERR(req))
+               goto out;
        if (!req)
                goto out_drop;
 
        ireq = inet_rsk(req);
-       treq = tcp_rsk(req);
 
-       req->mss = mss;
        ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
        ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
 
@@ -198,13 +208,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
            ipv6_addr_type(&ireq->ir_v6_rmt_addr) & IPV6_ADDR_LINKLOCAL)
                ireq->ir_iif = tcp_v6_iif(skb);
 
-       ireq->snd_wscale        = tcp_opt.snd_wscale;
-       ireq->sack_ok           = tcp_opt.sack_ok;
-       ireq->wscale_ok         = tcp_opt.wscale_ok;
-       ireq->tstamp_ok         = tcp_opt.saw_tstamp;
-       req->ts_recent          = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
-       treq->ts_off = tsoff;
-
        tcp_ao_syncookie(sk, skb, req, AF_INET6);
 
        /*
@@ -245,7 +248,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
                                  dst_metric(dst, RTAX_INITRWND));
 
        ireq->rcv_wscale = rcv_wscale;
-       ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, net, dst);
+       ireq->ecn_ok &= cookie_ecn_ok(net, dst);
 
        ret = tcp_get_cookie_sock(sk, skb, req, dst);
 out: