netdev - [PATCH v1 2/2] tcp: Ignore OOO handling for TCP ACKs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 20 Oct 2022 11:22:42 -0700
From:   Kamaljit Singh <kamaljit.singh1@....com>
To:     edumazet@...gle.com, davem@...emloft.net, yoshfuji@...ux-ipv6.org,
        dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com
Cc:     netdev@...r.kernel.org, Niklas.Cassel@....com,
        Damien.LeMoal@....com, kamaljit.singh1@....com
Subject: [PATCH v1 2/2] tcp: Ignore OOO handling for TCP ACKs

Even with the TCP window fix to tcp_acceptable_seq(), occasional
out-of-order host ACKs were still seen under heavy write workloads thus
Impacting performance.  By removing the OoO optionality for ACKs in
__tcp_transmit_skb() that issue seems to be fixed as well.

Signed-off-by: Kamaljit Singh <kamaljit.singh1@....com>
---
 net/ipv4/tcp_output.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 322e061edb72..1cd77493f32c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1307,7 +1307,10 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 	 * TODO: Ideally, in-flight pure ACK packets should not matter here.
 	 * One way to get this would be to set skb->truesize = 2 on them.
 	 */
-	skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
+	if (likely(tcb->tcp_flags & TCPHDR_ACK))
+		skb->ooo_okay = 0;
+	else
+		skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
 
 	/* If we had to use memory reserve to allocate this skb,
 	 * this might cause drops if packet is looped back :
-- 
2.25.1