Re: [PATCH nf-next v2] netfilter: conntrack: collect start time as early as possible

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Nov 05, 2024 at 06:32:47PM +0100, Florian Westphal wrote:
> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > Thanks, I'd rather convince you this is the way to go, if after
> > quickly sketching a patchset you think it is not worth for more
> > reasons, we can revisit.
> 
> Untested.  I'm not sure about skb_tstamp() usage.
> As-is CTA_EVENT_TIMESTAMP in the NEW event would be before
> the start time reported as the start time by the timestamp extension.

Is there any chance this timestamp can be enabled via toggle?

One comment below.

> diff --git a/include/net/netfilter/nf_conntrack_ecache.h b/include/net/netfilter/nf_conntrack_ecache.h
> --- a/include/net/netfilter/nf_conntrack_ecache.h
> +++ b/include/net/netfilter/nf_conntrack_ecache.h
> @@ -20,6 +20,7 @@ enum nf_ct_ecache_state {
>  
>  struct nf_conntrack_ecache {
>  	unsigned long cache;		/* bitops want long */
> +	u64 timestamp;			/* event timestamp, in nanoseconds */
>  	u16 ctmask;			/* bitmask of ct events to be delivered */
>  	u16 expmask;			/* bitmask of expect events to be delivered */
>  	u32 missed;			/* missed events */
> @@ -50,6 +51,7 @@ static inline bool nf_ct_ecache_exist(const struct nf_conn *ct)
>  /* This structure is passed to event handler */
>  struct nf_ct_event {
>  	struct nf_conn *ct;
> +	u64 timestamp;
>  	u32 portid;
>  	int report;
>  };
> @@ -73,7 +75,7 @@ void nf_ct_deliver_cached_events(struct nf_conn *ct);
>  int nf_conntrack_eventmask_report(unsigned int eventmask, struct nf_conn *ct,
>  				  u32 portid, int report);
>  
> -bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp);
> +bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, ktime_t tstamp, gfp_t gfp);
>  #else
>  
>  static inline void nf_ct_deliver_cached_events(const struct nf_conn *ct)
> @@ -88,7 +90,8 @@ static inline int nf_conntrack_eventmask_report(unsigned int eventmask,
>  	return 0;
>  }
>  
> -static inline bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp)
> +static inline bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask,
> +					ktime_t tstamp, gfp_t gfp)
>  {
>  	return false;
>  }
> @@ -108,6 +111,9 @@ nf_conntrack_event_cache(enum ip_conntrack_events event, struct nf_conn *ct)
>  	if (e == NULL)
>  		return;
>  
> +	if (READ_ONCE(e->cache) == 0)
> +		e->timestamp = ktime_get_real_ns();
> +
>  	set_bit(event, &e->cache);
>  #endif
>  }
> diff --git a/include/uapi/linux/netfilter/nfnetlink_conntrack.h b/include/uapi/linux/netfilter/nfnetlink_conntrack.h
> --- a/include/uapi/linux/netfilter/nfnetlink_conntrack.h
> +++ b/include/uapi/linux/netfilter/nfnetlink_conntrack.h
> @@ -57,6 +57,7 @@ enum ctattr_type {
>  	CTA_SYNPROXY,
>  	CTA_FILTER,
>  	CTA_STATUS_MASK,
> +	CTA_EVENT_TIMESTAMP,

        CTA_TIMESTAMP_EVENT

for consistency with CTA_TIMESTAMP_{START,...}

>  	__CTA_MAX
>  };
>  #define CTA_MAX (__CTA_MAX - 1)
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -1791,6 +1791,7 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
>  	if ((ecache || net->ct.sysctl_events) &&
>  	    !nf_ct_ecache_ext_add(ct, ecache ? ecache->ctmask : 0,
>  				  ecache ? ecache->expmask : 0,
> +				  ktime_to_ns(skb_get_ktime(skb)),
>  				  GFP_ATOMIC)) {
>  		nf_conntrack_free(ct);
>  		return ERR_PTR(-ENOMEM);
> diff --git a/net/netfilter/nf_conntrack_ecache.c b/net/netfilter/nf_conntrack_ecache.c
> index 69948e1d6974..661d69da6d9a 100644
> --- a/net/netfilter/nf_conntrack_ecache.c
> +++ b/net/netfilter/nf_conntrack_ecache.c
> @@ -182,6 +182,7 @@ int nf_conntrack_eventmask_report(unsigned int events, struct nf_conn *ct,
>  	item.ct = ct;
>  	item.portid = e->portid ? e->portid : portid;
>  	item.report = report;
> +	item.timestamp = e->timestamp;
>  
>  	/* This is a resent of a destroy event? If so, skip missed */
>  	missed = e->portid ? 0 : e->missed;
> @@ -297,7 +298,7 @@ void nf_conntrack_ecache_work(struct net *net, enum nf_ct_ecache_state state)
>  	}
>  }
>  
> -bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp)
> +bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, ktime_t tstamp, gfp_t gfp)
>  {
>  	struct net *net = nf_ct_net(ct);
>  	struct nf_conntrack_ecache *e;
> @@ -326,6 +327,7 @@ bool nf_ct_ecache_ext_add(struct nf_conn *ct, u16 ctmask, u16 expmask, gfp_t gfp
>  
>  	e = nf_ct_ext_add(ct, NF_CT_EXT_ECACHE, gfp);
>  	if (e) {
> +		e->timestamp = tstamp;
>  		e->ctmask  = ctmask;
>  		e->expmask = expmask;
>  	}
> diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
> index 6a1239433830..e6b908a1cfef 100644
> --- a/net/netfilter/nf_conntrack_netlink.c
> +++ b/net/netfilter/nf_conntrack_netlink.c
> @@ -717,6 +717,7 @@ static size_t ctnetlink_nlmsg_size(const struct nf_conn *ct)
>  #endif
>  	       + ctnetlink_proto_size(ct)
>  	       + ctnetlink_label_size(ct)
> +	       + nla_total_size(sizeof(u64)) /* CTA_EVENT_TIMESTAMP */
>  	       ;
>  }
>  
> @@ -1557,6 +1558,7 @@ static const struct nla_policy ct_nla_policy[CTA_MAX+1] = {
>  				    .len = NF_CT_LABELS_MAX_SIZE },
>  	[CTA_FILTER]		= { .type = NLA_NESTED },
>  	[CTA_STATUS_MASK]	= { .type = NLA_U32 },
> +	[CTA_EVENT_TIMESTAMP]	= { .type = NLA_U64 },
>  };
>  
>  static int ctnetlink_flush_iterate(struct nf_conn *ct, void *data)
> @@ -2304,7 +2306,7 @@ ctnetlink_create_conntrack(struct net *net,
>  
>  	nf_ct_acct_ext_add(ct, GFP_ATOMIC);
>  	nf_ct_tstamp_ext_add(ct, GFP_ATOMIC);
> -	nf_ct_ecache_ext_add(ct, 0, 0, GFP_ATOMIC);
> +	nf_ct_ecache_ext_add(ct, 0, 0, 0, GFP_ATOMIC);
>  	nf_ct_labels_ext_add(ct);
>  	nfct_seqadj_ext_add(ct);
>  	nfct_synproxy_ext_add(ct);
> diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
> index 67a41cd2baaf..c57d3715287d 100644
> --- a/net/netfilter/nft_ct.c
> +++ b/net/netfilter/nft_ct.c
> @@ -322,7 +322,7 @@ static void nft_ct_set_eval(const struct nft_expr *expr,
>  		}
>  
>  		if (ctmask && !nf_ct_is_confirmed(ct))
> -			nf_ct_ecache_ext_add(ct, ctmask, 0, GFP_ATOMIC);
> +			nf_ct_ecache_ext_add(ct, ctmask, 0, skb_tstamp(skb), GFP_ATOMIC);
>  		break;
>  	}
>  #endif
> diff --git a/net/netfilter/xt_CT.c b/net/netfilter/xt_CT.c
> index 2be2f7a7b60f..b2563bcf0c17 100644
> --- a/net/netfilter/xt_CT.c
> +++ b/net/netfilter/xt_CT.c
> @@ -189,7 +189,7 @@ static int xt_ct_tg_check(const struct xt_tgchk_param *par,
>  
>  	if ((info->ct_events || info->exp_events) &&
>  	    !nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
> -				  GFP_KERNEL)) {
> +				  0, GFP_KERNEL)) {
>  		ret = -EINVAL;
>  		goto err3;
>  	}