* [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT
@ 2025-03-25 11:03 Jiayuan Chen
2025-03-25 11:29 ` Eric Dumazet
0 siblings, 1 reply; 5+ messages in thread
From: Jiayuan Chen @ 2025-03-25 11:03 UTC (permalink / raw)
To: netdev
Cc: linux-kernel, edumazet, kuniyu, davem, kuba, pabeni, horms,
dsahern, ncardwell, mrpre, Jiayuan Chen
PAWS is a long-standing issue, especially when there are upstream network
devices, making it more prone to occur.
Currently, packet loss statistics for PAWS can only be viewed through MIB,
which is a global metric and cannot be precisely obtained through tracing
to get the specific 4-tuple of the dropped packet. In the past, we had to
use kprobe ret to retrieve relevant skb information from
tcp_timewait_state_process().
We add a drop_reason pointer, similar to what previous commit does:
commit e34100c2ecbb ("tcp: add a drop_reason pointer to tcp_check_req()")
This commit addresses the PAWSESTABREJECTED case and also sets the
corresponding drop reason.
We use 'pwru' to test.
Before this commit:
''''
./pwru 'port 9999'
2025/03/24 13:46:03 Listening for events..
TUPLE FUNC
172.31.75.115:12345->172.31.75.114:9999(tcp) sk_skb_reason_drop(SKB_DROP_REASON_NOT_SPECIFIED)
'''
After this commit:
'''
./pwru 'port 9999'
2025/03/24 16:06:59 Listening for events..
TUPLE FUNC
172.31.75.115:12345->172.31.75.114:9999(tcp) sk_skb_reason_drop(SKB_DROP_REASON_TCP_RFC7323_PAWS)
'''
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
My apologize.
I struggled for a long time to get packetdrill to fix the client port, but
ultimately failed to do so, which is why I couldn't provide a packetdrill
script.
Instead, I wrote my own program to trigger PAWS, which can be found at
https://github.com/mrpre/nettrigger/tree/main
---
include/net/tcp.h | 3 ++-
net/ipv4/tcp_ipv4.c | 2 +-
net/ipv4/tcp_minisocks.c | 7 +++++--
net/ipv6/tcp_ipv6.c | 2 +-
4 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index f8efe56bbccb..e1574e804530 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -427,7 +427,8 @@ enum tcp_tw_status {
enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
struct sk_buff *skb,
const struct tcphdr *th,
- u32 *tw_isn);
+ u32 *tw_isn,
+ enum skb_drop_reason *drop_reason);
struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
struct request_sock *req, bool fastopen,
bool *lost_race, enum skb_drop_reason *drop_reason);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1cd0938d47e0..a9dde473a23f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2417,7 +2417,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
goto csum_error;
}
- tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn);
+ tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn, &drop_reason);
switch (tw_status) {
case TCP_TW_SYN: {
struct sock *sk2 = inet_lookup_listener(net,
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index fb9349be36b8..d16dfd41397e 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -97,7 +97,8 @@ static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq,
*/
enum tcp_tw_status
tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
- const struct tcphdr *th, u32 *tw_isn)
+ const struct tcphdr *th, u32 *tw_isn,
+ enum skb_drop_reason *drop_reason)
{
struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
u32 rcv_nxt = READ_ONCE(tcptw->tw_rcv_nxt);
@@ -245,8 +246,10 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
return TCP_TW_SYN;
}
- if (paws_reject)
+ if (paws_reject) {
+ *drop_reason = SKB_DROP_REASON_TCP_RFC7323_PAWS;
__NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
+ }
if (!th->rst) {
/* In this case we must reset the TIMEWAIT timer.
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c134cf1a603a..8862e315edc5 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1970,7 +1970,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
goto csum_error;
}
- tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn);
+ tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn, &drop_reason);
switch (tw_status) {
case TCP_TW_SYN:
{
--
2.47.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT
2025-03-25 11:03 [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT Jiayuan Chen
@ 2025-03-25 11:29 ` Eric Dumazet
2025-03-25 12:20 ` Jiayuan Chen
0 siblings, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2025-03-25 11:29 UTC (permalink / raw)
To: Jiayuan Chen
Cc: netdev, linux-kernel, kuniyu, davem, kuba, pabeni, horms, dsahern,
ncardwell, mrpre
On Tue, Mar 25, 2025 at 12:03 PM Jiayuan Chen <jiayuan.chen@linux.dev> wrote:
>
> PAWS is a long-standing issue, especially when there are upstream network
> devices, making it more prone to occur.
>
> Currently, packet loss statistics for PAWS can only be viewed through MIB,
> which is a global metric and cannot be precisely obtained through tracing
> to get the specific 4-tuple of the dropped packet. In the past, we had to
> use kprobe ret to retrieve relevant skb information from
> tcp_timewait_state_process().
>
> We add a drop_reason pointer, similar to what previous commit does:
> commit e34100c2ecbb ("tcp: add a drop_reason pointer to tcp_check_req()")
>
> This commit addresses the PAWSESTABREJECTED case and also sets the
> corresponding drop reason.
>
> We use 'pwru' to test.
>
> Before this commit:
> ''''
> ./pwru 'port 9999'
> 2025/03/24 13:46:03 Listening for events..
> TUPLE FUNC
> 172.31.75.115:12345->172.31.75.114:9999(tcp) sk_skb_reason_drop(SKB_DROP_REASON_NOT_SPECIFIED)
> '''
>
> After this commit:
> '''
> ./pwru 'port 9999'
> 2025/03/24 16:06:59 Listening for events..
> TUPLE FUNC
> 172.31.75.115:12345->172.31.75.114:9999(tcp) sk_skb_reason_drop(SKB_DROP_REASON_TCP_RFC7323_PAWS)
> '''
>
> Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
> ---
> My apologize.
> I struggled for a long time to get packetdrill to fix the client port, but
> ultimately failed to do so, which is why I couldn't provide a packetdrill
> script.
> Instead, I wrote my own program to trigger PAWS, which can be found at
> https://github.com/mrpre/nettrigger/tree/main
> ---
> include/net/tcp.h | 3 ++-
> net/ipv4/tcp_ipv4.c | 2 +-
> net/ipv4/tcp_minisocks.c | 7 +++++--
> net/ipv6/tcp_ipv6.c | 2 +-
> 4 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index f8efe56bbccb..e1574e804530 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -427,7 +427,8 @@ enum tcp_tw_status {
> enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
> struct sk_buff *skb,
> const struct tcphdr *th,
> - u32 *tw_isn);
> + u32 *tw_isn,
> + enum skb_drop_reason *drop_reason);
> struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
> struct request_sock *req, bool fastopen,
> bool *lost_race, enum skb_drop_reason *drop_reason);
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 1cd0938d47e0..a9dde473a23f 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -2417,7 +2417,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
> goto csum_error;
> }
>
> - tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn);
> + tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn, &drop_reason);
> switch (tw_status) {
> case TCP_TW_SYN: {
> struct sock *sk2 = inet_lookup_listener(net,
> diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> index fb9349be36b8..d16dfd41397e 100644
> --- a/net/ipv4/tcp_minisocks.c
> +++ b/net/ipv4/tcp_minisocks.c
> @@ -97,7 +97,8 @@ static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq,
> */
> enum tcp_tw_status
> tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
> - const struct tcphdr *th, u32 *tw_isn)
> + const struct tcphdr *th, u32 *tw_isn,
> + enum skb_drop_reason *drop_reason)
> {
> struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
> u32 rcv_nxt = READ_ONCE(tcptw->tw_rcv_nxt);
> @@ -245,8 +246,10 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
> return TCP_TW_SYN;
> }
>
> - if (paws_reject)
> + if (paws_reject) {
> + *drop_reason = SKB_DROP_REASON_TCP_RFC7323_PAWS;
> __NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
I think we should add a new SNMP value and drop reason for TW sockets.
SNMP_MIB_ITEM("PAWSTimewait", LINUX_MIB_PAWSTIMEWAIT),
and SKB_DROP_REASON_TCP_RFC7323_TW_PAWS ?
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT
2025-03-25 11:29 ` Eric Dumazet
@ 2025-03-25 12:20 ` Jiayuan Chen
2025-03-25 15:43 ` Jakub Kicinski
0 siblings, 1 reply; 5+ messages in thread
From: Jiayuan Chen @ 2025-03-25 12:20 UTC (permalink / raw)
To: Eric Dumazet
Cc: netdev, linux-kernel, kuniyu, davem, kuba, pabeni, horms, dsahern,
ncardwell, mrpre
March 25, 2025 at 19:29, "Eric Dumazet" <edumazet@google.com> wrote:
> > ---
> >
> > include/net/tcp.h | 3 ++-
> >
> > net/ipv4/tcp_ipv4.c | 2 +-
> >
> > net/ipv4/tcp_minisocks.c | 7 +++++--
> >
> > net/ipv6/tcp_ipv6.c | 2 +-
> >
> > 4 files changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/net/tcp.h b/include/net/tcp.h
> >
> > index f8efe56bbccb..e1574e804530 100644
> >
> > --- a/include/net/tcp.h
> >
> > +++ b/include/net/tcp.h
> >
> > @@ -427,7 +427,8 @@ enum tcp_tw_status {
> >
> > enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
> >
> > struct sk_buff *skb,
> >
> > const struct tcphdr *th,
> >
> > - u32 *tw_isn);
> >
> > + u32 *tw_isn,
> >
> > + enum skb_drop_reason *drop_reason);
> >
> > struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
> >
> > struct request_sock *req, bool fastopen,
> >
> > bool *lost_race, enum skb_drop_reason *drop_reason);
> >
> > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> >
> > index 1cd0938d47e0..a9dde473a23f 100644
> >
> > --- a/net/ipv4/tcp_ipv4.c
> >
> > +++ b/net/ipv4/tcp_ipv4.c
> >
> > @@ -2417,7 +2417,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
> >
> > goto csum_error;
> >
> > }
> >
> > - tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn);
> >
> > + tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn, &drop_reason);
> >
> > switch (tw_status) {
> >
> > case TCP_TW_SYN: {
> >
> > struct sock *sk2 = inet_lookup_listener(net,
> >
> > diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> >
> > index fb9349be36b8..d16dfd41397e 100644
> >
> > --- a/net/ipv4/tcp_minisocks.c
> >
> > +++ b/net/ipv4/tcp_minisocks.c
> >
> > @@ -97,7 +97,8 @@ static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq,
> >
> > */
> >
> > enum tcp_tw_status
> >
> > tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
> >
> > - const struct tcphdr *th, u32 *tw_isn)
> >
> > + const struct tcphdr *th, u32 *tw_isn,
> >
> > + enum skb_drop_reason *drop_reason)
> >
> > {
> >
> > struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
> >
> > u32 rcv_nxt = READ_ONCE(tcptw->tw_rcv_nxt);
> >
> > @@ -245,8 +246,10 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
> >
> > return TCP_TW_SYN;
> >
> > }
> >
> > - if (paws_reject)
> >
> > + if (paws_reject) {
> >
> > + *drop_reason = SKB_DROP_REASON_TCP_RFC7323_PAWS;
> >
> > __NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
> >
>
> I think we should add a new SNMP value and drop reason for TW sockets.
>
> SNMP_MIB_ITEM("PAWSTimewait", LINUX_MIB_PAWSTIMEWAIT),
>
> and SKB_DROP_REASON_TCP_RFC7323_TW_PAWS ?
>
That makes sense, we've done similar things before, such as adding
PAWS_OLD_ACK previously.
Thanks for the suggestion!
--
pw-bot: cr
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT
2025-03-25 12:20 ` Jiayuan Chen
@ 2025-03-25 15:43 ` Jakub Kicinski
2025-03-25 16:18 ` Jiayuan Chen
0 siblings, 1 reply; 5+ messages in thread
From: Jakub Kicinski @ 2025-03-25 15:43 UTC (permalink / raw)
To: Jiayuan Chen
Cc: Eric Dumazet, netdev, linux-kernel, kuniyu, davem, pabeni, horms,
dsahern, ncardwell, mrpre
On Tue, 25 Mar 2025 12:20:18 +0000 Jiayuan Chen wrote:
> pw-bot: cr
Interesting, so you know about pw-bot commands but neither about
the 24h reposting cool down time, nor about the fact that net-next
is closed..
Please read:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT
2025-03-25 15:43 ` Jakub Kicinski
@ 2025-03-25 16:18 ` Jiayuan Chen
0 siblings, 0 replies; 5+ messages in thread
From: Jiayuan Chen @ 2025-03-25 16:18 UTC (permalink / raw)
To: Jakub Kicinski
Cc: Eric Dumazet, netdev, linux-kernel, kuniyu, davem, pabeni, horms,
dsahern, ncardwell, mrpre
March 25, 2025 at 23:43, "Jakub Kicinski" <kuba@kernel.org> wrote:
>
> On Tue, 25 Mar 2025 12:20:18 +0000 Jiayuan Chen wrote:
>
> >
> > pw-bot: cr
> >
>
> Interesting, so you know about pw-bot commands but neither about
> the 24h reposting cool down time, nor about the fact that net-next
> is closed..
>
> Please read:
>
> https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
>
My apologies, I learned the pw-bot commands from other maintainers' email
responses and then discovered that I could set the patchwork status.
I'll learn the documentation more thoroughly next.
Please ingore my patch; I'll resubmit it after the merge window closes.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2025-03-25 16:18 UTC | newest]
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2025-03-25 11:03 [PATCH net-next v2] tcp: Support skb PAWS drop reason when TIME-WAIT Jiayuan Chen
2025-03-25 11:29 ` Eric Dumazet
2025-03-25 12:20 ` Jiayuan Chen
2025-03-25 15:43 ` Jakub Kicinski
2025-03-25 16:18 ` Jiayuan Chen
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