Date:   Mon, 27 May 2019 19:40:07 +0000
From:   Kevin 'ldir' Darbyshire-Bryant <ldir@...byshire-bryant.me.uk>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v5] net: sched: Introduce act_ctinfo action

I have to call it a day.  I have no idea why the patches are becoming corrupt and hence how to fix it, it’s probably something Apple has done to git, or maybe MS to my email server.

Sadly I also think that the only way this patch/functionality will ever be acceptable is if someone else writes it, where they or their company can take the credit/blame.

I tried very hard to approach the process of upstream submission in a positive way, seeking advice & guidance in the form of RFC patches, many rounds later I feel they’re further away from acceptance than ever.  Clearly it is not desired functionality/code otherwise it would have been written by now and I cannot face another 3 rounds of the same thing for act_ctinfo user space, the x_tables/nf_tables kernel helper to store the DSCP in the first place and the user space code to handle that.

As a rank outsider, amateur coder I shall leave it that I’ve found the process completely discouraging.  The professionals are of course paid to deal with this.


> On 27 May 2019, at 16:47, Toke Høiland-Jørgensen <toke@...hat.com> wrote:
> 
> Kevin 'ldir' Darbyshire-Bryant <ldir@...byshire-bryant.me.uk> writes:
> 
>> ctinfo is a new tc filter action module.  It is designed to restore
>> information contained in firewall conntrack marks to other packet fields
>> and is typically used on packet ingress paths.  At present it has two
>> independent sub-functions or operating modes, DSCP restoration mode &
>> skb mark restoration mode.
>> 
>> The DSCP restore mode:
>> 
>> This mode copies DSCP values that have been placed in the firewall
>> conntrack mark back into the IPv4/v6 diffserv fields of relevant
>> packets.
>> 
>> The DSCP restoration is intended for use and has been found useful for
>> restoring ingress classifications based on egress classifications across
>> links that bleach or otherwise change DSCP, typically home ISP Internet
>> links.  Restoring DSCP on ingress on the WAN link allows qdiscs such as
>> but by no means limited to CAKE to shape inbound packets according to
>> policies that are easier to set & mark on egress.
>> 
>> Ingress classification is traditionally a challenging task since
>> iptables rules haven't yet run and tc filter/eBPF programs are pre-NAT
>> lookups, hence are unable to see internal IPv4 addresses as used on the
>> typical home masquerading gateway.  Thus marking the connection in some
>> manner on egress for later restoration of classification on ingress is
>> easier to implement.
>> 
>> Parameters related to DSCP restore mode:
>> 
>> dscpmask - a 32 bit mask of 6 contiguous bits and indicate bits of the
>> conntrack mark field contain the DSCP value to be restored.
>> 
>> statemask - a 32 bit mask of (usually) 1 bit length, outside the area
>> specified by dscpmask.  This represents a conditional operation flag
>> whereby the DSCP is only restored if the flag is set.  This is useful to
>> implement a 'one shot' iptables based classification where the
>> 'complicated' iptables rules are only run once to classify the
>> connection on initial (egress) packet and subsequent packets are all
>> marked/restored with the same DSCP.  A mask of zero disables the
>> conditional behaviour ie. the conntrack mark DSCP bits are always
>> restored to the ip diffserv field (assuming the conntrack entry is found
>> & the skb is an ipv4/ipv6 type)
>> 
>> e.g. dscpmask 0xfc000000 statemask 0x01000000
>> 
>> |----0xFC----conntrack mark----000000---|
>> | Bits 31-26 | bit 25 | bit24 |~~~ Bit 0|
>> | DSCP       | unused | flag  |unused   |
>> |-----------------------0x01---000000---|
>>      |                   |
>>      |                   |
>>      ---|             Conditional flag
>>         v             only restore if set
>> |-ip diffserv-|
>> | 6 bits      |
>> |-------------|
>> 
>> The skb mark restore mode (cpmark):
>> 
>> This mode copies the firewall conntrack mark to the skb's mark field.
>> It is completely the functional equivalent of the existing act_connmark
>> action with the additional feature of being able to apply a mask to the
>> restored value.
>> 
>> Parameters related to skb mark restore mode:
>> 
>> mask - a 32 bit mask applied to the firewall conntrack mark to mask out
>> bits unwanted for restoration.  This can be useful where the conntrack
>> mark is being used for different purposes by different applications.  If
>> not specified and by default the whole mark field is copied (i.e.
>> default mask of 0xffffffff)
>> 
>> e.g. mask 0x00ffffff to mask out the top 8 bits being used by the
>> aforementioned DSCP restore mode.
>> 
>> |----0x00----conntrack mark----ffffff---|
>> | Bits 31-24 |                          |
>> | DSCP & flag|      some value here     |
>> |---------------------------------------|
>> 			|
>> 			|
>> 			v
>> |------------skb mark-------------------|
>> |            |                          |
>> |  zeroed    |                          |
>> |---------------------------------------|
>> 
>> Overall parameters:
>> 
>> zone - conntrack zone
>> 
>> control - action related control (reclassify | pipe | drop | continue |
>> ok | goto chain <CHAIN_INDEX>)
>> 
>> Mode specific values are passed as parameter structures across netlink.
>> Similarly statistics indicating DSCP & skb mark restoration counts are
>> also returned via netlink.
>> 
>> Signed-off-by: Kevin Darbyshire-Bryant <ldir@...byshire-bryant.me.uk>
> 
> I like the new commit message! :)
> 
>> ---
>> v2 - add equivalent connmark functionality with an enhancement
>>    to accept a mask
>>    pass statistics for each sub-function as individual netlink
>>    attributes and stop (ab)using overlimits, drops
>>    update the testing config correctly
>> v3 - fix a licensing silly & tidy up GPL boilerplate
>> v4 - drop stray copy paste inline
>>    reverse christmas tree local vars
>> v5 - rebase on net-next/master not net/master by mistake - doh! now
>>     applies!
> 
> Still getting errors from 'git am' for your email. It helps to add
> --ignore-whitespace, but then I get ^M line endings in the resulting
> file...
> 
>>     rename connmark to cpmark.
>>     always use structures across netlink to pass parameters.
>>     rework commit message to clarify modes & applicable parameters
>>     without getting bogged down in userspace syntax.
>>     restrict dscpmask parameter to 6 contiguous bits only instead
>>     of >=6 contiguous bits.
>>     re-order netlink TLV values into functional groupings.
>> 
>> include/net/tc_act/tc_ctinfo.h            |  28 ++
>> include/uapi/linux/pkt_cls.h              |   1 +
>> include/uapi/linux/tc_act/tc_ctinfo.h     |  52 +++
>> net/sched/Kconfig                         |  17 +
>> net/sched/Makefile                        |   1 +
>> net/sched/act_ctinfo.c                    | 415 ++++++++++++++++++++++
>> tools/testing/selftests/tc-testing/config |   1 +
>> 7 files changed, 515 insertions(+)
>> create mode 100644 include/net/tc_act/tc_ctinfo.h
>> create mode 100644 include/uapi/linux/tc_act/tc_ctinfo.h
>> create mode 100644 net/sched/act_ctinfo.c
>> 
>> diff --git a/include/net/tc_act/tc_ctinfo.h b/include/net/tc_act/tc_ctinfo.h
>> new file mode 100644
>> index 000000000000..d6a688571672
>> --- /dev/null
>> +++ b/include/net/tc_act/tc_ctinfo.h
>> @@ -0,0 +1,28 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef __NET_TC_CTINFO_H
>> +#define __NET_TC_CTINFO_H
>> +
>> +#include <net/act_api.h>
>> +
>> +struct tcf_ctinfo_params {
>> +	struct rcu_head rcu;
>> +	struct net *net;
>> +	u32 dscpmask;
>> +	u32 dscpstatemask;
>> +	u32 cpmarkmask;
>> +	u16 zone;
>> +	u8 mode;
>> +	u8 dscpmaskshift;
>> +};
>> +
>> +struct tcf_ctinfo {
>> +	struct tc_action common;
>> +	struct tcf_ctinfo_params __rcu *params;
>> +	u64 stats_dscp_set;
>> +	u64 stats_dscp_error;
>> +	u64 stats_cpmark_set;
>> +};
>> +
>> +#define to_ctinfo(a) ((struct tcf_ctinfo *)a)
>> +
>> +#endif /* __NET_TC_CTINFO_H */
>> diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
>> index 51a0496f78ea..a93680fc4bfa 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 000000000000..48c40f657575
>> --- /dev/null
>> +++ b/include/uapi/linux/tc_act/tc_ctinfo.h
>> @@ -0,0 +1,52 @@
>> +/* 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;
>> +};
>> +
>> +struct tc_ctinfo_dscp {
>> +	__u32 mask;
>> +	__u32 statemask;
>> +};
>> +
>> +struct tc_ctinfo_cpmark {
>> +	__u32 mask;
>> +};
>> +
>> +struct tc_ctinfo_stats_dscp {
>> +	__u64 set;
>> +	__u64 error;
>> +};
>> +
>> +struct tc_ctinfo_stats_cpmark {
>> +	__u64 set;
>> +};
> 
> Ugh, no, single-entry structs are not an improvement, sorry.
> 
> I get that you want to have descriptive names, but you already get that
> from the netlink type names. Besides, 'mask' and 'statemask' are not
> really dependent anyway; 'statemask' could reasonably be unset with no
> effect on the mask value, no?
> 
>> +enum {
>> +	TCA_CTINFO_UNSPEC,
>> +	TCA_CTINFO_PAD,
>> +	TCA_CTINFO_TM,
>> +	TCA_CTINFO_ACT,
>> +	TCA_CTINFO_ZONE,
>> +	TCA_CTINFO_PARMS_DSCP,
>> +	TCA_CTINFO_PARMS_CPMARK,
>> +	TCA_CTINFO_MODE_DSCP,
>> +	TCA_CTINFO_MODE_CPMARK,
>> +	TCA_CTINFO_STATS_DSCP,
>> +	TCA_CTINFO_STATS_CPMARK,
>> +	__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/net/sched/Kconfig b/net/sched/Kconfig
>> index 2c72d95c3050..d104f7ee26c7 100644
>> --- a/net/sched/Kconfig
>> +++ b/net/sched/Kconfig
>> @@ -877,6 +877,23 @@ config NET_ACT_CONNMARK
>> 	  To compile this code as a module, choose M here: the
>> 	  module will be called act_connmark.
>> 
>> +config NET_ACT_CTINFO
>> +        tristate "Netfilter Connection Mark Actions"
>> +        depends on NET_CLS_ACT && NETFILTER && IP_NF_IPTABLES
>> +        depends on NF_CONNTRACK && NF_CONNTRACK_MARK
>> +        help
>> +	  Say Y here to allow transfer of a connmark stored information.
>> +	  Current actions transfer connmark stored DSCP into
>> +	  ipv4/v6 diffserv and/or to transfer connmark to packet
>> +	  mark.  Both are useful for restoring egress based marks
>> +	  back onto ingress connections for qdisc priority mapping
>> +	  purposes.
>> +
>> +	  If unsure, say N.
>> +
>> +	  To compile this code as a module, choose M here: the
>> +	  module will be called act_ctinfo.
>> +
>> config NET_ACT_SKBMOD
>>         tristate "skb data modification action"
>>         depends on NET_CLS_ACT
>> diff --git a/net/sched/Makefile b/net/sched/Makefile
>> index 8a40431d7b5c..d54bfcbd7981 100644
>> --- a/net/sched/Makefile
>> +++ b/net/sched/Makefile
>> @@ -21,6 +21,7 @@ obj-$(CONFIG_NET_ACT_CSUM)	+= act_csum.o
>> obj-$(CONFIG_NET_ACT_VLAN)	+= act_vlan.o
>> obj-$(CONFIG_NET_ACT_BPF)	+= act_bpf.o
>> obj-$(CONFIG_NET_ACT_CONNMARK)	+= act_connmark.o
>> +obj-$(CONFIG_NET_ACT_CTINFO)	+= act_ctinfo.o
>> obj-$(CONFIG_NET_ACT_SKBMOD)	+= act_skbmod.o
>> obj-$(CONFIG_NET_ACT_IFE)	+= act_ife.o
>> obj-$(CONFIG_NET_IFE_SKBMARK)	+= act_meta_mark.o
>> diff --git a/net/sched/act_ctinfo.c b/net/sched/act_ctinfo.c
>> new file mode 100644
>> index 000000000000..efcb7e0b5491
>> --- /dev/null
>> +++ b/net/sched/act_ctinfo.c
>> @@ -0,0 +1,415 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/* net/sched/act_ctinfo.c  netfilter ctinfo connmark actions
>> + *
>> + * Copyright (c) 2019 Kevin Darbyshire-Bryant <ldir@...byshire-bryant.me.uk>
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/init.h>
>> +#include <linux/kernel.h>
>> +#include <linux/skbuff.h>
>> +#include <linux/rtnetlink.h>
>> +#include <linux/pkt_cls.h>
>> +#include <linux/ip.h>
>> +#include <linux/ipv6.h>
>> +#include <net/netlink.h>
>> +#include <net/pkt_sched.h>
>> +#include <net/act_api.h>
>> +#include <net/pkt_cls.h>
>> +#include <uapi/linux/tc_act/tc_ctinfo.h>
>> +#include <net/tc_act/tc_ctinfo.h>
>> +
>> +#include <net/netfilter/nf_conntrack.h>
>> +#include <net/netfilter/nf_conntrack_core.h>
>> +#include <net/netfilter/nf_conntrack_ecache.h>
>> +#include <net/netfilter/nf_conntrack_zones.h>
>> +
>> +static struct tc_action_ops act_ctinfo_ops;
>> +static unsigned int ctinfo_net_id;
>> +
>> +static void tcf_ctinfo_dscp_set(struct nf_conn *ct, struct tcf_ctinfo *ca,
>> +				struct tcf_ctinfo_params *cp,
>> +				struct sk_buff *skb, int wlen, int proto)
>> +{
>> +	u8 dscp, newdscp;
>> +
>> +	newdscp = (((ct->mark & cp->dscpmask) >> cp->dscpmaskshift) << 2) &
>> +		     ~INET_ECN_MASK;
>> +
>> +	switch (proto) {
>> +	case NFPROTO_IPV4:
>> +		dscp = ipv4_get_dsfield(ip_hdr(skb)) & ~INET_ECN_MASK;
>> +		if (dscp != newdscp) {
>> +			if (likely(!skb_try_make_writable(skb, wlen))) {
>> +				ipv4_change_dsfield(ip_hdr(skb),
>> +						    INET_ECN_MASK,
>> +						    newdscp);
>> +				ca->stats_dscp_set++;
>> +			} else {
>> +				ca->stats_dscp_error++;
>> +			}
>> +		}
>> +		break;
>> +	case NFPROTO_IPV6:
>> +		dscp = ipv6_get_dsfield(ipv6_hdr(skb)) & ~INET_ECN_MASK;
>> +		if (dscp != newdscp) {
>> +			if (likely(!skb_try_make_writable(skb, wlen))) {
>> +				ipv6_change_dsfield(ipv6_hdr(skb),
>> +						    INET_ECN_MASK,
>> +						    newdscp);
>> +				ca->stats_dscp_set++;
>> +			} else {
>> +				ca->stats_dscp_error++;
>> +			}
>> +		}
>> +		break;
>> +	default:
>> +		break;
>> +	}
>> +}
>> +
>> +static void tcf_ctinfo_cpmark_set(struct nf_conn *ct, struct tcf_ctinfo *ca,
>> +				  struct tcf_ctinfo_params *cp,
>> +				  struct sk_buff *skb)
>> +{
>> +	ca->stats_cpmark_set++;
>> +	skb->mark = ct->mark & cp->cpmarkmask;
>> +}
>> +
>> +static int tcf_ctinfo_act(struct sk_buff *skb, const struct tc_action *a,
>> +			  struct tcf_result *res)
>> +{
>> +	const struct nf_conntrack_tuple_hash *thash = NULL;
>> +	struct tcf_ctinfo *ca = to_ctinfo(a);
>> +	struct nf_conntrack_tuple tuple;
>> +	struct nf_conntrack_zone zone;
>> +	enum ip_conntrack_info ctinfo;
>> +	struct tcf_ctinfo_params *cp;
>> +	struct nf_conn *ct;
>> +	int proto, wlen;
>> +	int action;
>> +
>> +	cp = rcu_dereference_bh(ca->params);
>> +
>> +	tcf_lastuse_update(&ca->tcf_tm);
>> +	bstats_update(&ca->tcf_bstats, skb);
>> +	action = READ_ONCE(ca->tcf_action);
>> +
>> +	wlen = skb_network_offset(skb);
>> +	if (tc_skb_protocol(skb) == htons(ETH_P_IP)) {
>> +		wlen += sizeof(struct iphdr);
>> +		if (!pskb_may_pull(skb, wlen))
>> +			goto out;
>> +
>> +		proto = NFPROTO_IPV4;
>> +	} else if (tc_skb_protocol(skb) == htons(ETH_P_IPV6)) {
>> +		wlen += sizeof(struct ipv6hdr);
>> +		if (!pskb_may_pull(skb, wlen))
>> +			goto out;
>> +
>> +		proto = NFPROTO_IPV6;
>> +	} else {
>> +		goto out;
>> +	}
>> +
>> +	ct = nf_ct_get(skb, &ctinfo);
>> +	if (!ct) { /* look harder, usually ingress */
>> +		if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
>> +				       proto, cp->net, &tuple))
>> +			goto out;
>> +		zone.id = cp->zone;
>> +		zone.dir = NF_CT_DEFAULT_ZONE_DIR;
>> +
>> +		thash = nf_conntrack_find_get(cp->net, &zone, &tuple);
>> +		if (!thash)
>> +			goto out;
>> +
>> +		ct = nf_ct_tuplehash_to_ctrack(thash);
>> +	}
>> +
>> +	if (cp->mode & CTINFO_MODE_DSCP)
>> +		if (!cp->dscpstatemask || (ct->mark & cp->dscpstatemask))
>> +			tcf_ctinfo_dscp_set(ct, ca, cp, skb, wlen, proto);
>> +
>> +	if (cp->mode & CTINFO_MODE_CPMARK)
>> +		tcf_ctinfo_cpmark_set(ct, ca, cp, skb);
>> +
>> +	if (thash)
>> +		nf_ct_put(ct);
>> +out:
>> +	return action;
>> +}
>> +
>> +static const struct nla_policy ctinfo_policy[TCA_CTINFO_MAX + 1] = {
>> +	[TCA_CTINFO_ACT]	  = { .len = sizeof(struct tc_ctinfo) },
>> +	[TCA_CTINFO_ZONE]	  = { .type = NLA_U16 },
>> +	[TCA_CTINFO_PARMS_DSCP]   = { .len = sizeof(struct tc_ctinfo_dscp) },
>> +	[TCA_CTINFO_PARMS_CPMARK] = { .len = sizeof(struct tc_ctinfo_cpmark) },
> 
> The opaque structs mean that you'll actually get *less* netlink validation.
> 
>> +	[TCA_CTINFO_MODE_DSCP]    = { .type = NLA_FLAG },
>> +	[TCA_CTINFO_MODE_CPMARK]  = { .type = NLA_FLAG },
>> +};
>> +
>> +static int tcf_ctinfo_init(struct net *net, struct nlattr *nla,
>> +			   struct nlattr *est, struct tc_action **a,
>> +			   int ovr, int bind, bool rtnl_held,
>> +			   struct tcf_proto *tp,
>> +			   struct netlink_ext_ack *extack)
>> +{
>> +	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
>> +	struct tc_ctinfo_cpmark *cpmarkparm = NULL;
>> +	struct nlattr *tb[TCA_CTINFO_MAX + 1];
>> +	struct tcf_ctinfo_params *cp_new;
>> +	struct tcf_chain *goto_ch = NULL;
>> +	struct tc_ctinfo_dscp *dscpparm;
>> +	struct tcf_ctinfo *ci;
>> +	struct tc_ctinfo *actparm;
>> +	int ret = 0, err, i;
>> +
>> +	if (!nla)
>> +		return -EINVAL;
>> +
>> +	err = nla_parse_nested(tb, TCA_CTINFO_MAX, nla, ctinfo_policy, NULL);
>> +	if (err < 0)
>> +		return err;
>> +
>> +	if (!tb[TCA_CTINFO_ACT])
>> +		return -EINVAL;
>> +
>> +	if (tb[TCA_CTINFO_MODE_DSCP] && !tb[TCA_CTINFO_PARMS_DSCP])
>> +		return -EINVAL;
>> +
>> +	if (tb[TCA_CTINFO_PARMS_CPMARK])
>> +		cpmarkparm = nla_data(tb[TCA_CTINFO_PARMS_CPMARK]);
>> +
>> +	dscpparm = nla_data(tb[TCA_CTINFO_PARMS_DSCP]);
>> +	actparm = nla_data(tb[TCA_CTINFO_ACT]);
>> +
>> +	if (dscpparm) {
> 
> This is broken; you need to check if tb[TCA_CTINFO_PARMS_DSCP] is NULL
> *before* calling nla_data on it. The check afterwards will not fail, as
> nla_data() adds a constant value to the 0-pointer.
> 
> Maybe just move this whole validation into the
> 
> if(tb[TCA_CTINFO_MODE_DSCP])
> 
> check?
> 
>> +		/* need contiguous 6 bit mask */
>> +		i = dscpparm->mask ? __ffs(dscpparm->mask) : 0;
>> +		if ((~0 & (dscpparm->mask >> i)) != 0x3f)
>> +			return -EINVAL;
>> +		/* mask & statemask must not overlap */
>> +		if (dscpparm->mask & dscpparm->statemask)
>> +			return -EINVAL;
>> +	}
>> +
>> +	/* done the validation:now to the actual action allocation */
>> +	err = tcf_idr_check_alloc(tn, &actparm->index, a, bind);
>> +	if (!err) {
>> +		ret = tcf_idr_create(tn, actparm->index, est, a,
>> +				     &act_ctinfo_ops, bind, false);
>> +		if (ret) {
>> +			tcf_idr_cleanup(tn, actparm->index);
>> +			return ret;
>> +		}
>> +	} else if (err > 0) {
>> +		if (bind) /* don't override defaults */
>> +			return 0;
>> +		if (!ovr) {
>> +			tcf_idr_release(*a, bind);
>> +			return -EEXIST;
>> +		}
>> +	} else {
>> +		return err;
>> +	}
>> +
>> +	err = tcf_action_check_ctrlact(actparm->action, tp, &goto_ch, extack);
>> +	if (err < 0)
>> +		goto release_idr;
>> +
>> +	ci = to_ctinfo(*a);
>> +
>> +	cp_new = kzalloc(sizeof(*cp_new), GFP_KERNEL);
>> +	if (unlikely(!cp_new)) {
>> +		err = -ENOMEM;
>> +		goto put_chain;
>> +	}
>> +
>> +	cp_new->net = net;
>> +	cp_new->zone = tb[TCA_CTINFO_ZONE] ?
>> +			nla_get_u16(tb[TCA_CTINFO_ZONE]) : 0;
>> +	if (dscpparm) {
>> +		cp_new->dscpmask = dscpparm->mask;
>> +		cp_new->dscpmaskshift = cp_new->dscpmask ?
>> +				__ffs(cp_new->dscpmask) : 0;
>> +		cp_new->dscpstatemask = dscpparm->statemask;
>> +	}
>> +
>> +	if (cpmarkparm)
>> +		cp_new->cpmarkmask = cpmarkparm->mask;
>> +	else
>> +		cp_new->cpmarkmask = ~0;
>> +
>> +	if (tb[TCA_CTINFO_MODE_DSCP])
>> +		cp_new->mode |= CTINFO_MODE_DSCP;
>> +	else
>> +		cp_new->mode &= ~CTINFO_MODE_DSCP;
>> +
>> +	if (tb[TCA_CTINFO_MODE_CPMARK])
>> +		cp_new->mode |= CTINFO_MODE_CPMARK;
>> +	else
>> +		cp_new->mode &= ~CTINFO_MODE_CPMARK;
>> +
>> +	spin_lock_bh(&ci->tcf_lock);
>> +	goto_ch = tcf_action_set_ctrlact(*a, actparm->action, goto_ch);
>> +	rcu_swap_protected(ci->params, cp_new,
>> +			   lockdep_is_held(&ci->tcf_lock));
>> +	spin_unlock_bh(&ci->tcf_lock);
>> +
>> +	if (goto_ch)
>> +		tcf_chain_put_by_act(goto_ch);
>> +	if (cp_new)
>> +		kfree_rcu(cp_new, rcu);
>> +
>> +	if (ret == ACT_P_CREATED)
>> +		tcf_idr_insert(tn, *a);
>> +
>> +	return ret;
>> +
>> +put_chain:
>> +	if (goto_ch)
>> +		tcf_chain_put_by_act(goto_ch);
>> +release_idr:
>> +	tcf_idr_release(*a, bind);
>> +	return err;
>> +}
>> +
>> +static int tcf_ctinfo_dump(struct sk_buff *skb, struct tc_action *a,
>> +			   int bind, int ref)
>> +{
>> +	struct tcf_ctinfo *ci = to_ctinfo(a);
>> +	struct tc_ctinfo opt = {
>> +		.index   = ci->tcf_index,
>> +		.refcnt  = refcount_read(&ci->tcf_refcnt) - ref,
>> +		.bindcnt = atomic_read(&ci->tcf_bindcnt) - bind,
>> +	};
>> +	struct tc_ctinfo_stats_cpmark cpmarkstats;
>> +	unsigned char *b = skb_tail_pointer(skb);
>> +	struct tc_ctinfo_stats_dscp dscpstats;
>> +	struct tc_ctinfo_cpmark cpmarkparm;
>> +	struct tc_ctinfo_dscp dscpparm;
>> +	struct tcf_ctinfo_params *cp;
>> +	struct tcf_t t;
>> +
>> +	spin_lock_bh(&ci->tcf_lock);
>> +	cp = rcu_dereference_protected(ci->params,
>> +				       lockdep_is_held(&ci->tcf_lock));
>> +	opt.action = ci->tcf_action;
>> +
>> +	if (nla_put(skb, TCA_CTINFO_ACT, sizeof(opt), &opt))
>> +		goto nla_put_failure;
>> +
>> +	if (cp->mode & CTINFO_MODE_DSCP) {
>> +		dscpparm.mask = cp->dscpmask;
>> +		dscpparm.statemask = cp->dscpstatemask;
>> +		if (nla_put(skb, TCA_CTINFO_PARMS_DSCP, sizeof(dscpparm),
>> +			    &dscpparm))
>> +			goto nla_put_failure;
>> +
>> +		if (nla_put_flag(skb, TCA_CTINFO_MODE_DSCP))
>> +			goto nla_put_failure;
>> +
>> +		dscpstats.error = ci->stats_dscp_error;
>> +		dscpstats.set = ci->stats_dscp_set;
>> +		if (nla_put(skb, TCA_CTINFO_STATS_DSCP, sizeof(dscpstats),
>> +			    &dscpstats))
>> +			goto nla_put_failure;
>> +	}
>> +
>> +	if (cp->mode & CTINFO_MODE_CPMARK) {
>> +		cpmarkparm.mask = cp->cpmarkmask;
>> +		if (nla_put(skb, TCA_CTINFO_PARMS_CPMARK, sizeof(cpmarkparm),
>> +			    &cpmarkparm))
>> +			goto nla_put_failure;
>> +
>> +		if (nla_put_flag(skb, TCA_CTINFO_MODE_CPMARK))
>> +			goto nla_put_failure;
>> +
>> +		cpmarkstats.set = ci->stats_cpmark_set;
>> +		if (nla_put_u64_64bit(skb, TCA_CTINFO_STATS_CPMARK,
>> +				      ci->stats_cpmark_set, TCA_CTINFO_PAD))
>> +			goto nla_put_failure;
>> +	}
> 
> I think you should dump all the statistics no matter the configuration.
> The configuration might be changed at run-time, in which case the user
> will probably still want to see the old stats from before the change.
> 
>> +	if (cp->zone) {
>> +		if (nla_put_u16(skb, TCA_CTINFO_ZONE, cp->zone))
>> +			goto nla_put_failure;
>> +	}
> 
> The default zone is '0', so there will always be a zone set. I.e., don't
> leave out the attribute entirely here, just add it with a 0-value.
> 
>> +
>> +	tcf_tm_dump(&t, &ci->tcf_tm);
>> +	if (nla_put_64bit(skb, TCA_CTINFO_TM, sizeof(t), &t, TCA_CTINFO_PAD))
>> +		goto nla_put_failure;
>> +
>> +	spin_unlock_bh(&ci->tcf_lock);
>> +	return skb->len;
>> +
>> +nla_put_failure:
>> +	spin_unlock_bh(&ci->tcf_lock);
>> +	nlmsg_trim(skb, b);
>> +	return -1;
>> +}
>> +
>> +static int tcf_ctinfo_walker(struct net *net, struct sk_buff *skb,
>> +			     struct netlink_callback *cb, int type,
>> +			     const struct tc_action_ops *ops,
>> +			     struct netlink_ext_ack *extack)
>> +{
>> +	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
>> +
>> +	return tcf_generic_walker(tn, skb, cb, type, ops, extack);
>> +}
>> +
>> +static int tcf_ctinfo_search(struct net *net, struct tc_action **a, u32 index)
>> +{
>> +	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
>> +
>> +	return tcf_idr_search(tn, a, index);
>> +}
>> +
>> +static struct tc_action_ops act_ctinfo_ops = {
>> +	.kind	= "ctinfo",
>> +	.id	= TCA_ID_CTINFO,
>> +	.owner	= THIS_MODULE,
>> +	.act	= tcf_ctinfo_act,
>> +	.dump	= tcf_ctinfo_dump,
>> +	.init	= tcf_ctinfo_init,
>> +	.walk	= tcf_ctinfo_walker,
>> +	.lookup	= tcf_ctinfo_search,
>> +	.size	= sizeof(struct tcf_ctinfo),
>> +};
>> +
>> +static __net_init int ctinfo_init_net(struct net *net)
>> +{
>> +	struct tc_action_net *tn = net_generic(net, ctinfo_net_id);
>> +
>> +	return tc_action_net_init(tn, &act_ctinfo_ops);
>> +}
>> +
>> +static void __net_exit ctinfo_exit_net(struct list_head *net_list)
>> +{
>> +	tc_action_net_exit(net_list, ctinfo_net_id);
>> +}
>> +
>> +static struct pernet_operations ctinfo_net_ops = {
>> +	.init		= ctinfo_init_net,
>> +	.exit_batch	= ctinfo_exit_net,
>> +	.id		= &ctinfo_net_id,
>> +	.size		= sizeof(struct tc_action_net),
>> +};
>> +
>> +static int __init ctinfo_init_module(void)
>> +{
>> +	return tcf_register_action(&act_ctinfo_ops, &ctinfo_net_ops);
>> +}
>> +
>> +static void __exit ctinfo_cleanup_module(void)
>> +{
>> +	tcf_unregister_action(&act_ctinfo_ops, &ctinfo_net_ops);
>> +}
>> +
>> +module_init(ctinfo_init_module);
>> +module_exit(ctinfo_cleanup_module);
>> +MODULE_AUTHOR("Kevin Darbyshire-Bryant <ldir@...byshire-bryant.me.uk>");
>> +MODULE_DESCRIPTION("Connection tracking mark actions");
>> +MODULE_LICENSE("GPL");
>> diff --git a/tools/testing/selftests/tc-testing/config b/tools/testing/selftests/tc-testing/config
>> index 203302065458..b235efd55367 100644
>> --- a/tools/testing/selftests/tc-testing/config
>> +++ b/tools/testing/selftests/tc-testing/config
>> @@ -38,6 +38,7 @@ CONFIG_NET_ACT_CSUM=m
>> CONFIG_NET_ACT_VLAN=m
>> CONFIG_NET_ACT_BPF=m
>> CONFIG_NET_ACT_CONNMARK=m
>> +CONFIG_NET_ACT_CTINFO=m
>> CONFIG_NET_ACT_SKBMOD=m
>> CONFIG_NET_ACT_IFE=m
>> CONFIG_NET_ACT_TUNNEL_KEY=m
>> -- 
>> 2.20.1 (Apple Git-117)

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