Subject: Re: [PATCH RFC iproute2-next v3] tc: add support for action act_ctinfo

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Mon, 03 Jun 2019 11:15:13 +0200

Kevin 'ldir' Darbyshire-Bryant <[email-masked]> writes:

>> On 2 Jun 2019, at 21:39, Toke Høiland-Jørgensen <[email-masked]> wrote:
>> 
>> Kevin Darbyshire-Bryant <[email-masked]> writes:
>> 
>>> ctinfo is an action restoring data stored in conntrack marks to various
>>> fields.  At present it has two independent modes of operation,
>>> restoration of DSCP into IPv4/v6 diffserv and restoration of conntrack
>>> marks into packet skb marks.
>>> 
>>> It understands a number of parameters specific to this action in
>>> additional to the usual action syntax.  Each operating mode is
>>> independent of the other so all options are optional, however not
>>> specifying at least one mode is a bit pointless.
>>> 
>>> Usage: ... ctinfo [dscp mask[/statemask]] [cpmark [mask]] [zone ZONE]
>>> 		  [CONTROL] [index <INDEX>]
>> 
>> Yay, bikeshedding time! :)
>
> I see your bikeshed and raise you… a bus shelter :-)
>
>> 
>> As I said in reply to the kernel patch, the "X/Y" syntax usually means
>> "<value>/<mask applied to value>", where here they are just two
>> semi-related mask values. So I think it would be better to just make
>> 'statemask' its own parameter.
>
> Instead of creating another keyword how about we drop the ‘/‘ and
> make it a space separated optional parameter to ‘dscp’? eg.
>
> Usage: ... ctinfo [dscp mask [statemask]] [cpmark [mask]] blah blah

Sure, I can live with that :)

>> Other than that, just a few nits, below...
>> 
>>> DSCP mode
>>> 
>>> dscp enables copying of a DSCP store in the conntrack mark into the
>>> ipv4/v6 diffserv field.  The mask is a 32bit field and specifies where
>>> in the conntrack mark the DSCP value is stored.  It must be 6 contiguous
>>> bits long, e.g. 0xfc000000 would restore the DSCP from the upper 6 bits
>>> of the conntrack mark.
>>> 
>>> The DSCP copying may be optionally controlled by a statemask.  The
>>> statemask is a 32bit field, usually with a single bit set and must not
>>> overlap the dscp mask.  The DSCP restore operation will only take place
>>> if the corresponding bit/s in conntrack mark yield a non zero result.
>>> 
>>> eg. dscp 0xfc000000/0x01000000 would retrieve the DSCP from the top 6
>>> bits, whilst using bit 25 as a flag to do so.  Bit 26 is unused in this
>>> example.
>>> 
>>> CPMARK mode
>>> 
>>> cpmark enables copying of the conntrack mark to the packet skb mark.  In
>>> this mode it is completely equivalent to the existing act_connmark.
>>> Additional functionality is provided by the optional mask parameter,
>>> whereby the stored conntrack mark is logically anded with the cpmark
>>> mask before being stored into skb mark.  This allows shared usage of the
>>> conntrack mark between applications.
>>> 
>>> eg. cpmark 0x00ffffff would restore only the lower 24 bits of the
>>> conntrack mark, thus may be useful in the event that the upper 8 bits
>>> are used by the DSCP function.
>>> 
>>> Usage: ... ctinfo [dscp mask[/statemask]] [cpmark [mask]] [zone ZONE]
>>> 		  [CONTROL] [index <INDEX>]
>>> where :
>>> 	dscp MASK is the bitmask to restore DSCP
>>> 	     STATEMASK is the bitmask to determine conditional restoring
>>> 	cpmark MASK mask applied to restored packet mark
>>> 	ZONE is the conntrack zone
>>> 	CONTROL := reclassify | pipe | drop | continue | ok |
>>> 		   goto chain <CHAIN_INDEX>
>>> 
>>> Signed-off-by: Kevin Darbyshire-Bryant <[email-masked]>
>>> 
>>> ---
>>> v2 - fix whitespace issue in pkt_cls
>>>     fix most warnings from checkpatch - some lines still over 80 chars
>>>     due to long TLV names.
>>> v3 - fix some dangling else warnings.
>>>     refactor stats printing to please checkpatch.
>>>     send zone TLV even if default '0' zone.
>>>     now checkpatch clean even though I think some of the formatting
>>>     is horrible :-)
>>>     sending via google's smtp 'cos MS' exchange office365 appears
>>>     to mangle patches from git send-email.
>> 
>> Ah, so it wasn't just me having problems ;)
>
> No, though I’m still not clear what’s going on or when Microsoft
> improved(tm) it :-/

I think it just re-encodes it as base64 instead of quoted-printable.
Which makes 'git am' take the whitespace very literally; or maybe
Exchange is also recoding the whitespace in the process...

>>> include/uapi/linux/pkt_cls.h          |   1 +
>>> include/uapi/linux/tc_act/tc_ctinfo.h |  34 ++++
>>> tc/Makefile                           |   1 +
>>> tc/m_ctinfo.c                         | 262 ++++++++++++++++++++++++++
>>> 4 files changed, 298 insertions(+)
>>> create mode 100644 include/uapi/linux/tc_act/tc_ctinfo.h
>>> create mode 100644 tc/m_ctinfo.c
>>> 
>>> diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
>>> index 51a0496f..a93680fc 100644
>>> --- a/include/uapi/linux/pkt_cls.h
>>> +++ b/include/uapi/linux/pkt_cls.h
>>> @@ -105,6 +105,7 @@ enum tca_id {
>>> 	TCA_ID_IFE = TCA_ACT_IFE,
>>> 	TCA_ID_SAMPLE = TCA_ACT_SAMPLE,
>>> 	/* other actions go here */
>>> +	TCA_ID_CTINFO,
>>> 	__TCA_ID_MAX = 255
>>> };
>>> 
>>> diff --git a/include/uapi/linux/tc_act/tc_ctinfo.h b/include/uapi/linux/tc_act/tc_ctinfo.h
>>> new file mode 100644
>>> index 00000000..da803e05
>>> --- /dev/null
>>> +++ b/include/uapi/linux/tc_act/tc_ctinfo.h
>>> @@ -0,0 +1,34 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>>> +#ifndef __UAPI_TC_CTINFO_H
>>> +#define __UAPI_TC_CTINFO_H
>>> +
>>> +#include <linux/types.h>
>>> +#include <linux/pkt_cls.h>
>>> +
>>> +struct tc_ctinfo {
>>> +	tc_gen;
>>> +};
>>> +
>>> +enum {
>>> +	TCA_CTINFO_UNSPEC,
>>> +	TCA_CTINFO_PAD,
>>> +	TCA_CTINFO_TM,
>>> +	TCA_CTINFO_ACT,
>>> +	TCA_CTINFO_ZONE,
>>> +	TCA_CTINFO_PARMS_DSCP_MASK,
>>> +	TCA_CTINFO_PARMS_DSCP_STATEMASK,
>>> +	TCA_CTINFO_PARMS_CPMARK_MASK,
>>> +	TCA_CTINFO_STATS_DSCP_SET,
>>> +	TCA_CTINFO_STATS_DSCP_ERROR,
>>> +	TCA_CTINFO_STATS_CPMARK_SET,
>>> +	__TCA_CTINFO_MAX
>>> +};
>>> +
>>> +#define TCA_CTINFO_MAX (__TCA_CTINFO_MAX - 1)
>>> +
>>> +enum {
>>> +	CTINFO_MODE_DSCP	= BIT(0),
>>> +	CTINFO_MODE_CPMARK	= BIT(1)
>>> +};
>>> +
>>> +#endif
>>> diff --git a/tc/Makefile b/tc/Makefile
>>> index 1a305cf4..60abddee 100644
>>> --- a/tc/Makefile
>>> +++ b/tc/Makefile
>>> @@ -48,6 +48,7 @@ TCMODULES += m_csum.o
>>> TCMODULES += m_simple.o
>>> TCMODULES += m_vlan.o
>>> TCMODULES += m_connmark.o
>>> +TCMODULES += m_ctinfo.o
>>> TCMODULES += m_bpf.o
>>> TCMODULES += m_tunnel_key.o
>>> TCMODULES += m_sample.o
>>> diff --git a/tc/m_ctinfo.c b/tc/m_ctinfo.c
>>> new file mode 100644
>>> index 00000000..af5102bf
>>> --- /dev/null
>>> +++ b/tc/m_ctinfo.c
>>> @@ -0,0 +1,262 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +/*
>>> + * m_ctinfo.c		netfilter ctinfo mark action
>>> + *
>>> + * Copyright (c) 2019 Kevin Darbyshire-Bryant <[email-masked]>
>>> + */
>>> +
>>> +#include <stdio.h>
>>> +#include <stdlib.h>
>>> +#include <unistd.h>
>>> +#include <string.h>
>>> +#include "utils.h"
>>> +#include "tc_util.h"
>>> +#include <linux/tc_act/tc_ctinfo.h>
>>> +
>>> +static void
>>> +explain(void)
>>> +{
>>> +	fprintf(stderr,
>>> +		"Usage: ... ctinfo [dscp mask[/statemask]] [cpmark [mask]] [zone ZONE] [CONTROL] [index <INDEX>]\n"
>>> +		"where :\n"
>>> +		"\tdscp   MASK bitmask location of stored DSCP\n"
>>> +		"\t       STATEMASK bitmask to determine conditional restoring\n"
>>> +		"\tcpmark MASK mask applied to mark on restoration\n"
>>> +		"\tZONE is the conntrack zone\n"
>>> +		"\tCONTROL := reclassify | pipe | drop | continue | ok |\n"
>>> +		"\t           goto chain <CHAIN_INDEX>\n");
>>> +}
>>> +
>>> +static void
>>> +usage(void)
>>> +{
>>> +	explain();
>>> +	exit(-1);
>>> +}
>>> +
>>> +static int
>>> +parse_ctinfo(struct action_util *a, int *argc_p, char ***argv_p, int tca_id,
>>> +	     struct nlmsghdr *n)
>>> +{
>>> +	unsigned int cpmarkmask = 0, dscpmask = 0, dscpstatemask = 0;
>>> +	struct tc_ctinfo sel = {};
>>> +	unsigned short zone = 0;
>>> +	char **argv = *argv_p;
>>> +	struct rtattr *tail;
>>> +	int argc = *argc_p;
>>> +	int ok = 0;
>>> +
>>> +	while (argc > 0) {
>>> +		if (matches(*argv, "ctinfo") == 0) {
>>> +			ok = 1;
>>> +			argc--;
>>> +			argv++;
>>> +		} else if (matches(*argv, "help") == 0) {
>>> +			usage();
>>> +		} else {
>>> +			break;
>>> +		}
>>> +
>>> +	}
>>> +
>>> +	if (!ok) {
>>> +		explain();
>>> +		return -1;
>>> +	}
>>> +
>>> +	if (argc) {
>>> +		if (matches(*argv, "dscp") == 0) {
>>> +			NEXT_ARG();
>>> +			char *slash;
>>> +
>>> +			slash = strchr(*argv, '/');
>>> +			if (slash)
>>> +				*slash = '\0';
>>> +			if (get_u32(&dscpmask, *argv, 0)) {
>>> +				fprintf(stderr,
>>> +					"ctinfo: Illegal dscp \"mask\"\n");
>>> +				return -1;
>>> +			}
>> 
>> Not strictly necessary, but would it be nicer to the user to do the
>> 'must be exactly 6 bits' test here as well, in order to provide a
>> friendlier error message than just 'invalid’?
>
> Agreed.  Have implemented that in v4, need to test before sending..both after
> sleep :-)

Cool

>> 
>> Could also just add this via extack on the kernel side, of course…
>
> May I please dodge that particular bullet on this occasion?

Haha, yeah, otherwise I would have insisted on it on the kernel
submission ;)

>> 
>>> +			if (slash && get_u32(&dscpstatemask, slash + 1, 0)) {
>>> +				fprintf(stderr,
>>> +					"ctinfo: Illegal dscp \"statemask\"\n");
>>> +				return -1;
>>> +			}
>>> +			argc--;
>>> +			argv++;
>>> +		}
>>> +	}
>>> +
>>> +	/* cpmark has optional mask parameter, so the next arg might not  */
>>> +	/* exist, or it might be the next option, or it may actually be a */
>>> +	/* 32bit mask */
>>> +	if (argc) {
>>> +		if (matches(*argv, "cpmark") == 0) {
>>> +			if (NEXT_ARG_OK()) {
>>> +				NEXT_ARG_FWD();
>>> +				if (!get_u32(&cpmarkmask, *argv, 0))
>>> +					NEXT_ARG_FWD(); /* was a mask */
>>> +				else /* not a mask, use default */
>>> +					cpmarkmask = ~0;
>>> +			} else {
>>> +				NEXT_ARG_FWD();
>>> +			}
>>> +		}
>>> +	}
>>> +
>>> +	if (argc) {
>>> +		if (matches(*argv, "zone") == 0) {
>>> +			NEXT_ARG();
>>> +			if (get_u16(&zone, *argv, 10)) {
>>> +				fprintf(stderr, "ctinfo: Illegal \"zone\"\n");
>>> +				return -1;
>>> +			}
>>> +			argc--;
>>> +			argv++;
>>> +		}
>>> +	}
>>> +
>>> +	parse_action_control_dflt(&argc, &argv, &sel.action,
>>> +				  false, TC_ACT_PIPE);
>>> +
>>> +	if (argc) {
>>> +		if (matches(*argv, "index") == 0) {
>>> +			NEXT_ARG();
>>> +			if (get_u32(&sel.index, *argv, 10)) {
>>> +				fprintf(stderr, "ctinfo: Illegal \"index\"\n");
>>> +				return -1;
>>> +			}
>>> +			argc--;
>>> +			argv++;
>>> +		}
>>> +	}
>>> +
>>> +	tail = addattr_nest(n, MAX_MSG, tca_id);
>>> +	addattr_l(n, MAX_MSG, TCA_CTINFO_ACT, &sel, sizeof(sel));
>>> +	addattr16(n, MAX_MSG, TCA_CTINFO_ZONE, zone);
>>> +
>>> +	if (dscpmask)
>>> +		addattr32(n, MAX_MSG,
>>> +			  TCA_CTINFO_PARMS_DSCP_MASK, dscpmask);
>>> +
>>> +	if (dscpstatemask)
>>> +		addattr32(n, MAX_MSG,
>>> +			  TCA_CTINFO_PARMS_DSCP_STATEMASK, dscpstatemask);
>>> +
>>> +	if (cpmarkmask)
>>> +		addattr32(n, MAX_MSG,
>>> +			  TCA_CTINFO_PARMS_CPMARK_MASK, cpmarkmask);
>>> +
>>> +	addattr_nest_end(n, tail);
>>> +
>>> +	*argc_p = argc;
>>> +	*argv_p = argv;
>>> +	return 0;
>>> +}
>>> +
>>> +static void print_ctinfo_stats(FILE *f, struct rtattr *tb[TCA_CTINFO_MAX + 1])
>>> +{
>>> +	struct tcf_t *tm;
>>> +
>>> +	if (tb[TCA_CTINFO_TM]) {
>>> +		tm = RTA_DATA(tb[TCA_CTINFO_TM]);
>>> +
>>> +		print_tm(f, tm);
>>> +	}
>>> +
>>> +	if (tb[TCA_CTINFO_STATS_DSCP_SET])
>>> +		print_lluint(PRINT_ANY, "dscpset", " DSCP set %llu",
>>> +			     rta_getattr_u64(tb[TCA_CTINFO_STATS_DSCP_SET]));
>>> +	if (tb[TCA_CTINFO_STATS_DSCP_ERROR])
>>> +		print_lluint(PRINT_ANY, "dscperror", " error %llu",
>>> +			     rta_getattr_u64(tb[TCA_CTINFO_STATS_DSCP_ERROR]));
>>> +
>>> +	if (tb[TCA_CTINFO_STATS_CPMARK_SET])
>>> +		print_lluint(PRINT_ANY, "cpmarkset", " CPMARK set %llu",
>>> +			     rta_getattr_u64(tb[TCA_CTINFO_STATS_CPMARK_SET]));
>>> +}
>>> +
>>> +static int print_ctinfo(struct action_util *au, FILE *f, struct rtattr *arg)
>>> +{
>>> +	unsigned int cpmarkmask = ~0, dscpmask = 0, dscpstatemask = 0;
>>> +	struct rtattr *tb[TCA_CTINFO_MAX + 1];
>>> +	unsigned short zone = 0;
>>> +	struct tc_ctinfo *ci;
>>> +
>>> +	if (arg == NULL)
>>> +		return -1;
>>> +
>>> +	parse_rtattr_nested(tb, TCA_CTINFO_MAX, arg);
>>> +	if (!tb[TCA_CTINFO_ACT]) {
>>> +		print_string(PRINT_FP, NULL, "%s",
>>> +			     "[NULL ctinfo action parameters]");
>>> +		return -1;
>>> +	}
>>> +
>>> +	ci = RTA_DATA(tb[TCA_CTINFO_ACT]);
>>> +
>>> +	if (tb[TCA_CTINFO_PARMS_DSCP_MASK]) {
>>> +		if (RTA_PAYLOAD(tb[TCA_CTINFO_PARMS_DSCP_MASK]) >=
>>> +		    sizeof(__u32))
>>> +			dscpmask = rta_getattr_u32(
>>> +					tb[TCA_CTINFO_PARMS_DSCP_MASK]);
>>> +		else
>>> +			print_string(PRINT_FP, NULL, "%s",
>>> +				     "[invalid dscp mask parameter]");
>>> +	}
>>> +
>>> +	if (tb[TCA_CTINFO_PARMS_DSCP_STATEMASK]) {
>>> +		if (RTA_PAYLOAD(tb[TCA_CTINFO_PARMS_DSCP_STATEMASK]) >=
>>> +		    sizeof(__u32))
>>> +			dscpstatemask = rta_getattr_u32(
>>> +					tb[TCA_CTINFO_PARMS_DSCP_STATEMASK]);
>>> +		else
>>> +			print_string(PRINT_FP, NULL, "%s",
>>> +				     "[invalid dscp statemask parameter]");
>>> +	}
>>> +
>>> +	if (tb[TCA_CTINFO_PARMS_CPMARK_MASK]) {
>>> +		if (RTA_PAYLOAD(tb[TCA_CTINFO_PARMS_CPMARK_MASK]) >=
>>> +		    sizeof(__u32))
>>> +			cpmarkmask = rta_getattr_u32(
>>> +					tb[TCA_CTINFO_PARMS_CPMARK_MASK]);
>>> +		else
>>> +			print_string(PRINT_FP, NULL, "%s",
>>> +				     "[invalid cpmark mask parameter]");
>>> +	}
>>> +
>>> +	if (tb[TCA_CTINFO_ZONE] && RTA_PAYLOAD(tb[TCA_CTINFO_ZONE]) >=
>>> +	    sizeof(__u16))
>>> +		zone = rta_getattr_u16(tb[TCA_CTINFO_ZONE]);
>>> +
>>> +	print_string(PRINT_ANY, "kind", "%s ", "ctinfo");
>>> +	print_hu(PRINT_ANY, "zone", "zone %u", zone);
>>> +	print_action_control(f, " ", ci->action, "");
>>> +
>>> +	print_string(PRINT_FP, NULL, "%s", _SL_);
>>> +	print_uint(PRINT_ANY, "index", "\t index %u", ci->index);
>>> +	print_int(PRINT_ANY, "ref", " ref %d", ci->refcnt);
>>> +	print_int(PRINT_ANY, "bind", " bind %d", ci->bindcnt);
>>> +
>>> +	if (tb[TCA_CTINFO_PARMS_DSCP_MASK]) {
>>> +		print_0xhex(PRINT_ANY, "dscpmask", " dscp %#010llx", dscpmask);
>>> +		print_0xhex(PRINT_ANY, "dscpstatemask", "/%#010llx",
>>> +			    dscpstatemask);
>>> +	}
>>> +
>>> +	if (tb[TCA_CTINFO_PARMS_CPMARK_MASK])
>>> +		print_0xhex(PRINT_ANY, "mark", " mark %#010llx",
>>> cpmarkmask);
>> 
>> Should be 'cpmark' not 'mark', no?
>
> Yes it should.  The one that got away - squished :-)
>
> Thanks for looking through my code, can’t be a pleasant task, and spotting
> my bits of code blindness.
>
> Kevin