| 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
| ||
|
Message-Id: <20200430173543.41026-2-edumazet@google.com>
Date: Thu, 30 Apr 2020 10:35:41 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Soheil Hassas Yeganeh <soheil@...gle.com>,
Neal Cardwell <ncardwell@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/3] tcp: add tp->dup_ack_counter
In commit 86de5921a3d5 ("tcp: defer SACK compression after DupThresh")
I added a TCP_FASTRETRANS_THRESH bias to tp->compressed_ack in order
to enable sack compression only after 3 dupacks.
Since we plan to relax this rule for flows that involve
stacks not requiring this old rule, this patch adds
a distinct tp->dup_ack_counter.
This means the TCP_FASTRETRANS_THRESH value is now used
in a single location that a future patch can adjust:
if (tp->dup_ack_counter < TCP_FASTRETRANS_THRESH) {
tp->dup_ack_counter++;
goto send_now;
}
This patch also introduces tcp_sack_compress_send_ack()
helper to ease following patch comprehension.
This patch refines LINUX_MIB_TCPACKCOMPRESSED to not
count the acks that we had to send if the timer expires
or tcp_sack_compress_send_ack() is sending an ack.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Acked-by: Neal Cardwell <ncardwell@...gle.com>
---
include/linux/tcp.h | 1 +
net/ipv4/tcp_input.c | 36 +++++++++++++++++++++++++++---------
net/ipv4/tcp_output.c | 6 +++---
net/ipv4/tcp_timer.c | 8 +++++++-
4 files changed, 38 insertions(+), 13 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 421c99c12291994ce9f023fbedbc9089c8a5690d..2c6f87e9f0cf6f50b679a2e7d70181e057645a5e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -268,6 +268,7 @@ struct tcp_sock {
} rack;
u16 advmss; /* Advertised MSS */
u8 compressed_ack;
+ u8 dup_ack_counter;
u32 chrono_start; /* Start time in jiffies of a TCP chrono */
u32 chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
u8 chrono_type:2, /* current chronograph type */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bf4ced9273e8e84b95204db9bfe86867c0a3ee13..da777df0a0baefb3bef8c802c9b9b83ff38b9fc9 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4327,6 +4327,27 @@ static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
}
}
+static void tcp_sack_compress_send_ack(struct sock *sk)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (!tp->compressed_ack)
+ return;
+
+ if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
+ __sock_put(sk);
+
+ /* Since we have to send one ack finally,
+ * substract one from tp->compressed_ack to keep
+ * LINUX_MIB_TCPACKCOMPRESSED accurate.
+ */
+ NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
+ tp->compressed_ack - 1);
+
+ tp->compressed_ack = 0;
+ tcp_send_ack(sk);
+}
+
static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
{
struct tcp_sock *tp = tcp_sk(sk);
@@ -4355,8 +4376,7 @@ static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
* If the sack array is full, forget about the last one.
*/
if (this_sack >= TCP_NUM_SACKS) {
- if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
- tcp_send_ack(sk);
+ tcp_sack_compress_send_ack(sk);
this_sack--;
tp->rx_opt.num_sacks--;
sp--;
@@ -5275,15 +5295,13 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
if (tp->compressed_ack_rcv_nxt != tp->rcv_nxt) {
tp->compressed_ack_rcv_nxt = tp->rcv_nxt;
- if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
- NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
- tp->compressed_ack - TCP_FASTRETRANS_THRESH);
- tp->compressed_ack = 0;
+ tp->dup_ack_counter = 0;
}
-
- if (++tp->compressed_ack <= TCP_FASTRETRANS_THRESH)
+ if (tp->dup_ack_counter < TCP_FASTRETRANS_THRESH) {
+ tp->dup_ack_counter++;
goto send_now;
-
+ }
+ tp->compressed_ack++;
if (hrtimer_is_queued(&tp->compressed_ack_timer))
return;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ba4482130f08ea386913bfa5de3253e9bbfa3030..c414aeb1efa927c84bd4cd6afd0c21d46f049d5b 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -184,10 +184,10 @@ static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts,
{
struct tcp_sock *tp = tcp_sk(sk);
- if (unlikely(tp->compressed_ack > TCP_FASTRETRANS_THRESH)) {
+ if (unlikely(tp->compressed_ack)) {
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED,
- tp->compressed_ack - TCP_FASTRETRANS_THRESH);
- tp->compressed_ack = TCP_FASTRETRANS_THRESH;
+ tp->compressed_ack);
+ tp->compressed_ack = 0;
if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1)
__sock_put(sk);
}
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index c3f26dcd6704ee6b160c7a59667f82bc940f8cbe..ada046f425d248446a1aa8b1271cc35cab492be7 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -753,8 +753,14 @@ static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer)
bh_lock_sock(sk);
if (!sock_owned_by_user(sk)) {
- if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
+ if (tp->compressed_ack) {
+ /* Since we have to send one ack finally,
+ * substract one from tp->compressed_ack to keep
+ * LINUX_MIB_TCPACKCOMPRESSED accurate.
+ */
+ tp->compressed_ack--;
tcp_send_ack(sk);
+ }
} else {
if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
&sk->sk_tsq_flags))
--
2.26.2.303.gf8c07b1a785-goog
Powered by blists - more mailing lists