Re: [PATCH v2] tcp: Use BPF timeout setting for SYN ACK RTO

When setting RTO through BPF program, some SYN ACK packets were unaffected
and continued to use TCP_TIMEOUT_INIT constant. This patch adds timeout
option to struct request_sock. Option is initialized with TCP_TIMEOUT_INIT
and is reassigned through BPF using tcp_timeout_init call. SYN ACK
retransmits now use newly added timeout option.

Signed-off-by: Akhmat Karakotov <redacted>
---
 include/net/request_sock.h      | 2 ++
 net/ipv4/inet_connection_sock.c | 2 +-
 net/ipv4/tcp_input.c            | 8 +++++---
 net/ipv4/tcp_minisocks.c        | 4 ++--
 4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 29e41ff3ec93..144c39db9898 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h

@@ -70,6 +70,7 @@ struct request_sock {
        struct saved_syn                *saved_syn;
        u32                             secid;
        u32                             peer_secid;
+       u32                             timeout;
 };

 static inline struct request_sock *inet_reqsk(const struct sock *sk)

@@ -104,6 +105,7 @@ reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
        sk_node_init(&req_to_sk(req)->sk_node);
        sk_tx_queue_clear(req_to_sk(req));
        req->saved_syn = NULL;
+       req->timeout = 0;

        req->num_timeout = 0;
        req->num_retrans = 0;
        req->sk = NULL;

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 0d477c816309..c43cc1f22092 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c

@@ -870,7 +870,7 @@ static void reqsk_timer_handler(struct timer_list *t)

                if (req->num_timeout++ == 0)
                        atomic_dec(&queue->young);
-               timeo = min(TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
+               timeo = min(req->timeout << req->num_timeout, TCP_RTO_MAX);
                mod_timer(&req->rsk_timer, jiffies + timeo);

                if (!nreq)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3f7bd7ae7d7a..5c181dc4e96f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c

@@ -6706,6 +6706,7 @@ struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
                ireq->ireq_state = TCP_NEW_SYN_RECV;
                write_pnet(&ireq->ireq_net, sock_net(sk_listener));
                ireq->ireq_family = sk_listener->sk_family;
+               req->timeout = TCP_TIMEOUT_INIT;
        }

        return req;

@@ -6922,9 +6923,10 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
                sock_put(fastopen_sk);
        } else {
                tcp_rsk(req)->tfo_listener = false;
-               if (!want_cookie)
-                       inet_csk_reqsk_queue_hash_add(sk, req,
-                               tcp_timeout_init((struct sock *)req));
+               if (!want_cookie) {
+                       req->timeout = tcp_timeout_init((struct sock *)req);
+                       inet_csk_reqsk_queue_hash_add(sk, req, req->timeout);
+               }
                af_ops->send_synack(sk, dst, &fl, req, &foc,
                                    !want_cookie ? TCP_SYNACK_NORMAL :
                                                   TCP_SYNACK_COOKIE,

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 0a4f3f16140a..9724c9c6d331 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c

@@ -590,7 +590,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                         * it can be estimated (approximately)
                         * from another data.
                         */
-                       tmp_opt.ts_recent_stamp = ktime_get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->num_timeout);
+                       tmp_opt.ts_recent_stamp = ktime_get_seconds() - (req->timeout << req->num_timeout) / HZ;
                        paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
                }
        }

@@ -629,7 +629,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                    !inet_rtx_syn_ack(sk, req)) {
                        unsigned long expires = jiffies;

-                       expires += min(TCP_TIMEOUT_INIT << req->num_timeout,
+                       expires += min(req->timeout << req->num_timeout,
                                       TCP_RTO_MAX);
                        if (!fastopen)
                                mod_timer_pending(&req->rsk_timer, expires);
--

2.17.1