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

[Matthieu Baerts <matttbe@kernel.org>]

Hi Jason,

On 22/04/2024 05:01, Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> 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
-- 
Sponsored by the NGI0 Core fund.