From: Chia-Yu Chang <[email protected]>

Before this patch, retransmitted SYN/ACK did not have a specific synack_type;
however, the upcoming patch needs to distinguish between retransmitted and
non-retransmitted SYN/ACK for AccECN negotiation to transmit the fallback
SYN/ACK during AccECN negotiation. Therefore, this patch introduces a new
synack_type (TCP_SYNACK_RETRANS).

Signed-off-by: Chia-Yu Chang <[email protected]>
Acked-by: Paolo Abeni <[email protected]>

---
v6:
- Add new synack_type instead of moving the increment of num_retran.
---
 include/net/tcp.h     | 1 +
 net/ipv4/tcp_output.c | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index e0a5cf2f7818..607a4cb4984c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -541,6 +541,7 @@ enum tcp_synack_type {
        TCP_SYNACK_NORMAL,
        TCP_SYNACK_FASTOPEN,
        TCP_SYNACK_COOKIE,
+       TCP_SYNACK_RETRANS,
 };
 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
                                struct request_sock *req,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8039c726d235..5fa14a73d03f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3921,6 +3921,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, 
struct dst_entry *dst,
 
        switch (synack_type) {
        case TCP_SYNACK_NORMAL:
+       case TCP_SYNACK_RETRANS:
                skb_set_owner_edemux(skb, req_to_sk(req));
                break;
        case TCP_SYNACK_COOKIE:
@@ -4606,7 +4607,7 @@ int tcp_rtx_synack(const struct sock *sk, struct 
request_sock *req)
        /* Paired with WRITE_ONCE() in sock_setsockopt() */
        if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED)
                WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash());
-       res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
+       res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_RETRANS,
                                  NULL);
        if (!res) {
                TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
-- 
2.34.1


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