[net-next,v7,1/7] net: introduce rstreason to detect why the RST is sent

Commit Message

Jason Xing April 22, 2024, 3:01 a.m. UTC

From: Jason Xing <[e-mail]>

Add a new standalone file for the easy future extension to support
both active reset and passive reset in the TCP/DCCP/MPTCP protocols.

This patch only does the preparations for reset reason mechanism,
nothing else changes.

The reset reasons are divided into three parts:
1) reuse MP_TCPRST option for MPTCP
2) reuse drop reasons for passive reset in TCP
3) our own reasons which are not relying on other reasons at all

The benefits of a standalone reset reason are listed here:
1) it can cover more than one case, such as reset reasons in MPTCP,
active reset reasons.
2) people can easily/fastly understand and maintain this mechanism.
3) we get unified format of output with prefix stripped.
4) more new reset reasons are on the way
...

I will implement the basic codes of active/passive reset reason in
those three protocols, which are not complete for this moment. For
passive reset part in TCP, I only introduce the NO_SOCKET common case
which could be set as an example.

After this series applied, it will have the ability to open a new
gate to let other people contribute more reasons into it :)

Signed-off-by: Jason Xing <[e-mail]>
---
 include/net/rstreason.h | 144 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 include/net/rstreason.h

Comments

Matthieu Baerts (NGI0) April 22, 2024, 8:46 a.m. UTC | #1

Hi Jason,

On 22/04/2024 05:01, Jason Xing wrote:
> From: Jason Xing <[e-mail]>
> 
> Add a new standalone file for the easy future extension to support
> both active reset and passive reset in the TCP/DCCP/MPTCP protocols.

Thank you for looking at that!

(...)

> diff --git a/include/net/rstreason.h b/include/net/rstreason.h
> new file mode 100644
> index 000000000000..c57bc5413c17
> --- /dev/null
> +++ b/include/net/rstreason.h
> @@ -0,0 +1,144 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#ifndef _LINUX_RSTREASON_H
> +#define _LINUX_RSTREASON_H
> +#include <net/dropreason-core.h>
> +#include <uapi/linux/mptcp.h>
> +
> +#define DEFINE_RST_REASON(FN, FNe)	\
> +	FN(MPTCP_RST_EUNSPEC)		\
> +	FN(MPTCP_RST_EMPTCP)		\
> +	FN(MPTCP_RST_ERESOURCE)		\
> +	FN(MPTCP_RST_EPROHIBIT)		\
> +	FN(MPTCP_RST_EWQ2BIG)		\
> +	FN(MPTCP_RST_EBADPERF)		\
> +	FN(MPTCP_RST_EMIDDLEBOX)	\

Small detail: should it not make more sense to put the ones linked to
MPTCP at the end? I mean I guess MPTCP should be treated in second
priority: CONFIG_MPTCP could not be set, and the ones linked to TCP
should be more frequent, etc.

> +	FN(NOT_SPECIFIED)		\
> +	FN(NO_SOCKET)			\
> +	FNe(MAX)

(...)

> +/* Convert reset reasons in MPTCP to our own enum type */
> +static inline enum sk_rst_reason convert_mptcpreason(u32 reason)
> +{
> +	switch (reason) {
> +	case MPTCP_RST_EUNSPEC:
> +		return SK_RST_REASON_MPTCP_RST_EUNSPEC;
> +	case MPTCP_RST_EMPTCP:
> +		return SK_RST_REASON_MPTCP_RST_EMPTCP;
> +	case MPTCP_RST_ERESOURCE:
> +		return SK_RST_REASON_MPTCP_RST_ERESOURCE;
> +	case MPTCP_RST_EPROHIBIT:
> +		return SK_RST_REASON_MPTCP_RST_EPROHIBIT;
> +	case MPTCP_RST_EWQ2BIG:
> +		return SK_RST_REASON_MPTCP_RST_EWQ2BIG;
> +	case MPTCP_RST_EBADPERF:
> +		return SK_RST_REASON_MPTCP_RST_EBADPERF;
> +	case MPTCP_RST_EMIDDLEBOX:
> +		return SK_RST_REASON_MPTCP_RST_EMIDDLEBOX;
> +	default:
> +		/**
> +		 * It should not happen, or else errors may occur
> +		 * in MPTCP layer
> +		 */
> +		return SK_RST_REASON_ERROR;
> +	}
> +}

If this helper is only used on MPTCP, maybe better to move it to
net/mptcp/protocol.h (and to patch 5/7?)? We tried to isolate MPTCP code.

Also, maybe it is just me, but I'm not a big fan of the helper name:
convert_mptcpreason() (same for the "drop" one). I think it should at
least mention its "origin" (rst reason): e.g. something like
(sk_)rst_reason_convert_mptcp or (sk_)rst_convert_mptcp_reason() (or
mptcp_to_rst_reason())?

And (sk_)rst_reason_convert_(skb_)drop() (or skb_drop_to_rst_reason())?

> +/* Convert reset reasons in MPTCP to our own enum type */

I don't think this part is linked to MPTCP, right?

> +static inline enum sk_rst_reason convert_dropreason(enum skb_drop_reason reason)
> +{
> +	switch (reason) {
> +	case SKB_DROP_REASON_NOT_SPECIFIED:
> +		return SK_RST_REASON_NOT_SPECIFIED;
> +	case SKB_DROP_REASON_NO_SOCKET:
> +		return SK_RST_REASON_NO_SOCKET;
> +	default:
> +		/* If we don't have our own corresponding reason */
> +		return SK_RST_REASON_NOT_SPECIFIED;
> +	}
> +}

(This helper could be introduced in patch 4/7 because it is not used
before, but I'm fine either ways.)

> +#endif

Cheers,
Matt

Jason Xing April 22, 2024, 9:17 a.m. UTC | #2

Hello Matthieu,

On Mon, Apr 22, 2024 at 4:47 PM Matthieu Baerts <[e-mail]> wrote:
>
> Hi Jason,
>
> On 22/04/2024 05:01, Jason Xing wrote:
> > From: Jason Xing <[e-mail]>
> >
> > Add a new standalone file for the easy future extension to support
> > both active reset and passive reset in the TCP/DCCP/MPTCP protocols.
>
> Thank you for looking at that!

Thanks for the review!

>
> (...)
>
> > diff --git a/include/net/rstreason.h b/include/net/rstreason.h
> > new file mode 100644
> > index 000000000000..c57bc5413c17
> > --- /dev/null
> > +++ b/include/net/rstreason.h
> > @@ -0,0 +1,144 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +
> > +#ifndef _LINUX_RSTREASON_H
> > +#define _LINUX_RSTREASON_H
> > +#include <net/dropreason-core.h>
> > +#include <uapi/linux/mptcp.h>
> > +
> > +#define DEFINE_RST_REASON(FN, FNe)   \
> > +     FN(MPTCP_RST_EUNSPEC)           \
> > +     FN(MPTCP_RST_EMPTCP)            \
> > +     FN(MPTCP_RST_ERESOURCE)         \
> > +     FN(MPTCP_RST_EPROHIBIT)         \
> > +     FN(MPTCP_RST_EWQ2BIG)           \
> > +     FN(MPTCP_RST_EBADPERF)          \
> > +     FN(MPTCP_RST_EMIDDLEBOX)        \
>
> Small detail: should it not make more sense to put the ones linked to
> MPTCP at the end? I mean I guess MPTCP should be treated in second
> priority: CONFIG_MPTCP could not be set, and the ones linked to TCP
> should be more frequent, etc.

Do you mean that I need to adjust the order: 1) tcp reasons first, 2)
independent reasons, 3) mptcp reasons ?

Reasonable. I will do it :)

>
> > +     FN(NOT_SPECIFIED)               \
> > +     FN(NO_SOCKET)                   \
> > +     FNe(MAX)
>
> (...)
>
> > +/* Convert reset reasons in MPTCP to our own enum type */
> > +static inline enum sk_rst_reason convert_mptcpreason(u32 reason)
> > +{
> > +     switch (reason) {
> > +     case MPTCP_RST_EUNSPEC:
> > +             return SK_RST_REASON_MPTCP_RST_EUNSPEC;
> > +     case MPTCP_RST_EMPTCP:
> > +             return SK_RST_REASON_MPTCP_RST_EMPTCP;
> > +     case MPTCP_RST_ERESOURCE:
> > +             return SK_RST_REASON_MPTCP_RST_ERESOURCE;
> > +     case MPTCP_RST_EPROHIBIT:
> > +             return SK_RST_REASON_MPTCP_RST_EPROHIBIT;
> > +     case MPTCP_RST_EWQ2BIG:
> > +             return SK_RST_REASON_MPTCP_RST_EWQ2BIG;
> > +     case MPTCP_RST_EBADPERF:
> > +             return SK_RST_REASON_MPTCP_RST_EBADPERF;
> > +     case MPTCP_RST_EMIDDLEBOX:
> > +             return SK_RST_REASON_MPTCP_RST_EMIDDLEBOX;
> > +     default:
> > +             /**
> > +              * It should not happen, or else errors may occur
> > +              * in MPTCP layer
> > +              */
> > +             return SK_RST_REASON_ERROR;
> > +     }
> > +}
>
> If this helper is only used on MPTCP, maybe better to move it to
> net/mptcp/protocol.h (and to patch 5/7?)? We tried to isolate MPTCP code.

Roger that. I will move the helper into protocol.h as well as the patch itself.

>
> Also, maybe it is just me, but I'm not a big fan of the helper name:
> convert_mptcpreason() (same for the "drop" one). I think it should at
> least mention its "origin" (rst reason): e.g. something like
> (sk_)rst_reason_convert_mptcp or (sk_)rst_convert_mptcp_reason() (or
> mptcp_to_rst_reason())?
>
> And (sk_)rst_reason_convert_(skb_)drop() (or skb_drop_to_rst_reason())?

I agree with you. Actually I had a local patch where I used
sk_rst_reason_skbdrop() and sk_rst_reason_mptcpreason().
Interestingly, I changed them in this patch series due to the function
name being too long (which is my initial thought).

I will use sk_rst_convert_xxx_reason() as you suggested.

>
> > +/* Convert reset reasons in MPTCP to our own enum type */
>
> I don't think this part is linked to MPTCP, right?

Ah, copy-paste syndrome... Sorry, I will correct it.

>
> > +static inline enum sk_rst_reason convert_dropreason(enum skb_drop_reason reason)
> > +{
> > +     switch (reason) {
> > +     case SKB_DROP_REASON_NOT_SPECIFIED:
> > +             return SK_RST_REASON_NOT_SPECIFIED;
> > +     case SKB_DROP_REASON_NO_SOCKET:
> > +             return SK_RST_REASON_NO_SOCKET;
> > +     default:
> > +             /* If we don't have our own corresponding reason */
> > +             return SK_RST_REASON_NOT_SPECIFIED;
> > +     }
> > +}
>
> (This helper could be introduced in patch 4/7 because it is not used
> before, but I'm fine either ways.)

Good. It makes more sense.

Thanks,
Jason

Matthieu Baerts (NGI0) April 22, 2024, 10:05 a.m. UTC | #3

On 22/04/2024 11:17, Jason Xing wrote:> On Mon, Apr 22, 2024 at 4:47 PM
Matthieu Baerts <[e-mail]> wrote:
>> On 22/04/2024 05:01, Jason Xing wrote:
>>> From: Jason Xing <[e-mail]>

(...)

>>> diff --git a/include/net/rstreason.h b/include/net/rstreason.h
>>> new file mode 100644
>>> index 000000000000..c57bc5413c17
>>> --- /dev/null
>>> +++ b/include/net/rstreason.h
>>> @@ -0,0 +1,144 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>>> +
>>> +#ifndef _LINUX_RSTREASON_H
>>> +#define _LINUX_RSTREASON_H
>>> +#include <net/dropreason-core.h>
>>> +#include <uapi/linux/mptcp.h>
>>> +
>>> +#define DEFINE_RST_REASON(FN, FNe)   \
>>> +     FN(MPTCP_RST_EUNSPEC)           \
>>> +     FN(MPTCP_RST_EMPTCP)            \
>>> +     FN(MPTCP_RST_ERESOURCE)         \
>>> +     FN(MPTCP_RST_EPROHIBIT)         \
>>> +     FN(MPTCP_RST_EWQ2BIG)           \
>>> +     FN(MPTCP_RST_EBADPERF)          \
>>> +     FN(MPTCP_RST_EMIDDLEBOX)        \
>>
>> Small detail: should it not make more sense to put the ones linked to
>> MPTCP at the end? I mean I guess MPTCP should be treated in second
>> priority: CONFIG_MPTCP could not be set, and the ones linked to TCP
>> should be more frequent, etc.
> 
> Do you mean that I need to adjust the order: 1) tcp reasons first, 2)
> independent reasons, 3) mptcp reasons ?

Correct, it looks like it is a more "natural" order.

> Reasonable. I will do it :)

Thanks!

Cheers,
Matt

Simon Horman April 22, 2024, 6:27 p.m. UTC | #4

On Mon, Apr 22, 2024 at 11:01:03AM +0800, Jason Xing wrote:

...

> diff --git a/include/net/rstreason.h b/include/net/rstreason.h

...

> +/**
> + * There are three parts in order:
> + * 1) reset reason in MPTCP: only for MPTCP use
> + * 2) skb drop reason: relying on drop reasons for such as passive reset
> + * 3) independent reset reason: such as active reset reasons
> + */

Hi Jason,

A minor nit from my side.

'/**' denotes the beginning of a Kernel doc,
but other than that, this comment is not a Kernel doc.

FWIIW, I would suggest providing a proper Kernel doc for enum sk_rst_reason.
But another option would be to simply make this a normal comment,
starting with "/* There are"

> +enum sk_rst_reason {

...

Jason Xing April 23, 2024, 2:14 a.m. UTC | #5

Hi Simon,

On Tue, Apr 23, 2024 at 2:28 AM Simon Horman <[e-mail]> wrote:
>
> On Mon, Apr 22, 2024 at 11:01:03AM +0800, Jason Xing wrote:
>
> ...
>
> > diff --git a/include/net/rstreason.h b/include/net/rstreason.h
>
> ...
>
> > +/**
> > + * There are three parts in order:
> > + * 1) reset reason in MPTCP: only for MPTCP use
> > + * 2) skb drop reason: relying on drop reasons for such as passive reset
> > + * 3) independent reset reason: such as active reset reasons
> > + */
>
> Hi Jason,
>
> A minor nit from my side.
>
> '/**' denotes the beginning of a Kernel doc,
> but other than that, this comment is not a Kernel doc.
>
> FWIIW, I would suggest providing a proper Kernel doc for enum sk_rst_reason.
> But another option would be to simply make this a normal comment,
> starting with "/* There are"

Thanks Simon. I'm trying to use the kdoc way to make it right :)

How about this one:
/**
 * enum sk_rst_reason - the reasons of socket reset
 *
 * The reason of skb drop, which is used in DCCP/TCP/MPTCP protocols.
 *
 * There are three parts in order:
 * 1) skb drop reasons: relying on drop reasons for such as passive
reset
 * 2) independent reset reasons: such as active reset reasons
 * 3) reset reasons in MPTCP: only for MPTCP use
 */
?

I chose to mimic what enum skb_drop_reason does in the
include/net/dropreason-core.h file.

> +enum sk_rst_reason {
> +       /**
> +        * Copy from include/uapi/linux/mptcp.h.
> +        * These reset fields will not be changed since they adhere to
> +        * RFC 8684. So do not touch them. I'm going to list each definition
> +        * of them respectively.
> +        */

Thanks to you, I found another similar point where I smell something
wrong as in the above code. I'm going to replace '/**' with '/*' since
it's only a comment, not a kdoc.

Thanks,
Jason

Jason Xing April 23, 2024, 2:17 a.m. UTC | #6

On Tue, Apr 23, 2024 at 10:14 AM Jason Xing <[e-mail]> wrote:
>
> Hi Simon,
>
> On Tue, Apr 23, 2024 at 2:28 AM Simon Horman <[e-mail]> wrote:
> >
> > On Mon, Apr 22, 2024 at 11:01:03AM +0800, Jason Xing wrote:
> >
> > ...
> >
> > > diff --git a/include/net/rstreason.h b/include/net/rstreason.h
> >
> > ...
> >
> > > +/**
> > > + * There are three parts in order:
> > > + * 1) reset reason in MPTCP: only for MPTCP use
> > > + * 2) skb drop reason: relying on drop reasons for such as passive reset
> > > + * 3) independent reset reason: such as active reset reasons
> > > + */
> >
> > Hi Jason,
> >
> > A minor nit from my side.
> >
> > '/**' denotes the beginning of a Kernel doc,
> > but other than that, this comment is not a Kernel doc.
> >
> > FWIIW, I would suggest providing a proper Kernel doc for enum sk_rst_reason.
> > But another option would be to simply make this a normal comment,
> > starting with "/* There are"
>
> Thanks Simon. I'm trying to use the kdoc way to make it right :)
>
> How about this one:
> /**
>  * enum sk_rst_reason - the reasons of socket reset
>  *
>  * The reason of skb drop, which is used in DCCP/TCP/MPTCP protocols.

s/skb drop/sk reset/

Sorry, I cannot withdraw my previous email in time.

>  *
>  * There are three parts in order:
>  * 1) skb drop reasons: relying on drop reasons for such as passive
> reset
>  * 2) independent reset reasons: such as active reset reasons
>  * 3) reset reasons in MPTCP: only for MPTCP use
>  */
> ?
>
> I chose to mimic what enum skb_drop_reason does in the
> include/net/dropreason-core.h file.
>
> > +enum sk_rst_reason {
> > +       /**
> > +        * Copy from include/uapi/linux/mptcp.h.
> > +        * These reset fields will not be changed since they adhere to
> > +        * RFC 8684. So do not touch them. I'm going to list each definition
> > +        * of them respectively.
> > +        */
>
> Thanks to you, I found another similar point where I smell something
> wrong as in the above code. I'm going to replace '/**' with '/*' since
> it's only a comment, not a kdoc.
>
> Thanks,
> Jason

Simon Horman April 23, 2024, 11:57 a.m. UTC | #7

On Tue, Apr 23, 2024 at 10:17:31AM +0800, Jason Xing wrote:
> On Tue, Apr 23, 2024 at 10:14 AM Jason Xing <[e-mail]> wrote:
> >
> > Hi Simon,
> >
> > On Tue, Apr 23, 2024 at 2:28 AM Simon Horman <[e-mail]> wrote:
> > >
> > > On Mon, Apr 22, 2024 at 11:01:03AM +0800, Jason Xing wrote:
> > >
> > > ...
> > >
> > > > diff --git a/include/net/rstreason.h b/include/net/rstreason.h
> > >
> > > ...
> > >
> > > > +/**
> > > > + * There are three parts in order:
> > > > + * 1) reset reason in MPTCP: only for MPTCP use
> > > > + * 2) skb drop reason: relying on drop reasons for such as passive reset
> > > > + * 3) independent reset reason: such as active reset reasons
> > > > + */
> > >
> > > Hi Jason,
> > >
> > > A minor nit from my side.
> > >
> > > '/**' denotes the beginning of a Kernel doc,
> > > but other than that, this comment is not a Kernel doc.
> > >
> > > FWIIW, I would suggest providing a proper Kernel doc for enum sk_rst_reason.
> > > But another option would be to simply make this a normal comment,
> > > starting with "/* There are"
> >
> > Thanks Simon. I'm trying to use the kdoc way to make it right :)
> >
> > How about this one:
> > /**
> >  * enum sk_rst_reason - the reasons of socket reset
> >  *
> >  * The reason of skb drop, which is used in DCCP/TCP/MPTCP protocols.
> 
> s/skb drop/sk reset/
> 
> Sorry, I cannot withdraw my previous email in time.
> 
> >  *
> >  * There are three parts in order:
> >  * 1) skb drop reasons: relying on drop reasons for such as passive
> > reset
> >  * 2) independent reset reasons: such as active reset reasons
> >  * 3) reset reasons in MPTCP: only for MPTCP use
> >  */
> > ?
> >
> > I chose to mimic what enum skb_drop_reason does in the
> > include/net/dropreason-core.h file.
> >
> > > +enum sk_rst_reason {
> > > +       /**
> > > +        * Copy from include/uapi/linux/mptcp.h.
> > > +        * These reset fields will not be changed since they adhere to
> > > +        * RFC 8684. So do not touch them. I'm going to list each definition
> > > +        * of them respectively.
> > > +        */
> >
> > Thanks to you, I found another similar point where I smell something
> > wrong as in the above code. I'm going to replace '/**' with '/*' since
> > it's only a comment, not a kdoc.

Likewise, thanks Jason.

I haven't had time to look at v8 properly,
but I see that kernel-doc is happy with the changed
you have made there as discussed above.

Jason Xing April 23, 2024, 12:03 p.m. UTC | #8

On Tue, Apr 23, 2024 at 7:57 PM Simon Horman <[e-mail]> wrote:
>
> On Tue, Apr 23, 2024 at 10:17:31AM +0800, Jason Xing wrote:
> > On Tue, Apr 23, 2024 at 10:14 AM Jason Xing <[e-mail]> wrote:
> > >
> > > Hi Simon,
> > >
> > > On Tue, Apr 23, 2024 at 2:28 AM Simon Horman <[e-mail]> wrote:
> > > >
> > > > On Mon, Apr 22, 2024 at 11:01:03AM +0800, Jason Xing wrote:
> > > >
> > > > ...
> > > >
> > > > > diff --git a/include/net/rstreason.h b/include/net/rstreason.h
> > > >
> > > > ...
> > > >
> > > > > +/**
> > > > > + * There are three parts in order:
> > > > > + * 1) reset reason in MPTCP: only for MPTCP use
> > > > > + * 2) skb drop reason: relying on drop reasons for such as passive reset
> > > > > + * 3) independent reset reason: such as active reset reasons
> > > > > + */
> > > >
> > > > Hi Jason,
> > > >
> > > > A minor nit from my side.
> > > >
> > > > '/**' denotes the beginning of a Kernel doc,
> > > > but other than that, this comment is not a Kernel doc.
> > > >
> > > > FWIIW, I would suggest providing a proper Kernel doc for enum sk_rst_reason.
> > > > But another option would be to simply make this a normal comment,
> > > > starting with "/* There are"
> > >
> > > Thanks Simon. I'm trying to use the kdoc way to make it right :)
> > >
> > > How about this one:
> > > /**
> > >  * enum sk_rst_reason - the reasons of socket reset
> > >  *
> > >  * The reason of skb drop, which is used in DCCP/TCP/MPTCP protocols.
> >
> > s/skb drop/sk reset/
> >
> > Sorry, I cannot withdraw my previous email in time.
> >
> > >  *
> > >  * There are three parts in order:
> > >  * 1) skb drop reasons: relying on drop reasons for such as passive
> > > reset
> > >  * 2) independent reset reasons: such as active reset reasons
> > >  * 3) reset reasons in MPTCP: only for MPTCP use
> > >  */
> > > ?
> > >
> > > I chose to mimic what enum skb_drop_reason does in the
> > > include/net/dropreason-core.h file.
> > >
> > > > +enum sk_rst_reason {
> > > > +       /**
> > > > +        * Copy from include/uapi/linux/mptcp.h.
> > > > +        * These reset fields will not be changed since they adhere to
> > > > +        * RFC 8684. So do not touch them. I'm going to list each definition
> > > > +        * of them respectively.
> > > > +        */
> > >
> > > Thanks to you, I found another similar point where I smell something
> > > wrong as in the above code. I'm going to replace '/**' with '/*' since
> > > it's only a comment, not a kdoc.
>
> Likewise, thanks Jason.
>
> I haven't had time to look at v8 properly,
> but I see that kernel-doc is happy with the changed
> you have made there as discussed above.
>

Thank you, Simon. I learned something new about the coding style.

Besides, some other nit problems have been spotted by Matt. I will fix
them if it's required to send a new version.

Patch

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
new file mode 100644
index 000000000000..c57bc5413c17
--- /dev/null
+++ b/include/net/rstreason.h
@@ -0,0 +1,144 @@ 
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _LINUX_RSTREASON_H
+#define _LINUX_RSTREASON_H
+#include <net/dropreason-core.h>
+#include <uapi/linux/mptcp.h>
+
+#define DEFINE_RST_REASON(FN, FNe)	\
+	FN(MPTCP_RST_EUNSPEC)		\
+	FN(MPTCP_RST_EMPTCP)		\
+	FN(MPTCP_RST_ERESOURCE)		\
+	FN(MPTCP_RST_EPROHIBIT)		\
+	FN(MPTCP_RST_EWQ2BIG)		\
+	FN(MPTCP_RST_EBADPERF)		\
+	FN(MPTCP_RST_EMIDDLEBOX)	\
+	FN(NOT_SPECIFIED)		\
+	FN(NO_SOCKET)			\
+	FNe(MAX)
+
+/**
+ * There are three parts in order:
+ * 1) reset reason in MPTCP: only for MPTCP use
+ * 2) skb drop reason: relying on drop reasons for such as passive reset
+ * 3) independent reset reason: such as active reset reasons
+ */
+enum sk_rst_reason {
+	/**
+	 * Copy from include/uapi/linux/mptcp.h.
+	 * These reset fields will not be changed since they adhere to
+	 * RFC 8684. So do not touch them. I'm going to list each definition
+	 * of them respectively.
+	 */
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_EUNSPEC: Unspecified error.
+	 * This is the default error; it implies that the subflow is no
+	 * longer available. The presence of this option shows that the
+	 * RST was generated by an MPTCP-aware device.
+	 */
+	SK_RST_REASON_MPTCP_RST_EUNSPEC,
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_EMPTCP: MPTCP-specific error.
+	 * An error has been detected in the processing of MPTCP options.
+	 * This is the usual reason code to return in the cases where a RST
+	 * is being sent to close a subflow because of an invalid response.
+	 */
+	SK_RST_REASON_MPTCP_RST_EMPTCP,
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_ERESOURCE: Lack of resources.
+	 * This code indicates that the sending host does not have enough
+	 * resources to support the terminated subflow.
+	 */
+	SK_RST_REASON_MPTCP_RST_ERESOURCE,
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_EPROHIBIT: Administratively prohibited.
+	 * This code indicates that the requested subflow is prohibited by
+	 * the policies of the sending host.
+	 */
+	SK_RST_REASON_MPTCP_RST_EPROHIBIT,
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_EWQ2BIG: Too much outstanding data.
+	 * This code indicates that there is an excessive amount of data
+	 * that needs to be transmitted over the terminated subflow while
+	 * having already been acknowledged over one or more other subflows.
+	 * This may occur if a path has been unavailable for a short period
+	 * and it is more efficient to reset and start again than it is to
+	 * retransmit the queued data.
+	 */
+	SK_RST_REASON_MPTCP_RST_EWQ2BIG,
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_EBADPERF: Unacceptable performance.
+	 * This code indicates that the performance of this subflow was
+	 * too low compared to the other subflows of this Multipath TCP
+	 * connection.
+	 */
+	SK_RST_REASON_MPTCP_RST_EBADPERF,
+	/**
+	 * @SK_RST_REASON_MPTCP_RST_EMIDDLEBOX: Middlebox interference.
+	 * Middlebox interference has been detected over this subflow,
+	 * making MPTCP signaling invalid. For example, this may be sent
+	 * if the checksum does not validate.
+	 */
+	SK_RST_REASON_MPTCP_RST_EMIDDLEBOX,
+
+	/**
+	 * Refer to include/net/dropreason-core.h
+	 * Rely on skb drop reason because it indicates exactly why RST
+	 * could happen.
+	 */
+	/** @SK_RST_REASON_NOT_SPECIFIED: reset reason is not specified */
+	SK_RST_REASON_NOT_SPECIFIED,
+	/** @SK_RST_REASON_NO_SOCKET: no valid socket that can be used */
+	SK_RST_REASON_NO_SOCKET,
+
+	/** @SK_RST_REASON_ERROR: unexpected error happens */
+	SK_RST_REASON_ERROR,
+
+	/**
+	 * @SK_RST_REASON_MAX: Maximum of socket reset reasons.
+	 * It shouldn't be used as a real 'reason'.
+	 */
+	SK_RST_REASON_MAX,
+};
+
+/* Convert reset reasons in MPTCP to our own enum type */
+static inline enum sk_rst_reason convert_mptcpreason(u32 reason)
+{
+	switch (reason) {
+	case MPTCP_RST_EUNSPEC:
+		return SK_RST_REASON_MPTCP_RST_EUNSPEC;
+	case MPTCP_RST_EMPTCP:
+		return SK_RST_REASON_MPTCP_RST_EMPTCP;
+	case MPTCP_RST_ERESOURCE:
+		return SK_RST_REASON_MPTCP_RST_ERESOURCE;
+	case MPTCP_RST_EPROHIBIT:
+		return SK_RST_REASON_MPTCP_RST_EPROHIBIT;
+	case MPTCP_RST_EWQ2BIG:
+		return SK_RST_REASON_MPTCP_RST_EWQ2BIG;
+	case MPTCP_RST_EBADPERF:
+		return SK_RST_REASON_MPTCP_RST_EBADPERF;
+	case MPTCP_RST_EMIDDLEBOX:
+		return SK_RST_REASON_MPTCP_RST_EMIDDLEBOX;
+	default:
+		/**
+		 * It should not happen, or else errors may occur
+		 * in MPTCP layer
+		 */
+		return SK_RST_REASON_ERROR;
+	}
+}
+
+/* Convert reset reasons in MPTCP to our own enum type */
+static inline enum sk_rst_reason convert_dropreason(enum skb_drop_reason reason)
+{
+	switch (reason) {
+	case SKB_DROP_REASON_NOT_SPECIFIED:
+		return SK_RST_REASON_NOT_SPECIFIED;
+	case SKB_DROP_REASON_NO_SOCKET:
+		return SK_RST_REASON_NO_SOCKET;
+	default:
+		/* If we don't have our own corresponding reason */
+		return SK_RST_REASON_NOT_SPECIFIED;
+	}
+}
+#endif