Subject: Re: [PATCH] netfilter: extend CONFIG_NF_CONNTRACK compile time checks

From: Pablo Neira Ayuso <[email-masked]>
Date: Tue, 11 Jan 2022 10:46:49 +0100

Hi,

On Sat, Dec 25, 2021 at 09:37:44AM -0800, [email-masked] wrote:
> From: Tom Rix <[email-masked]>
> 
> Extends
> commit 83ace77f5117 ("netfilter: ctnetlink: remove get_ct indirection")
> 
> Add some compile time checks by following the ct and ctinfo variables
> that are only set when CONFIG_NF_CONNTRACK is enabled.
> 
> In nfulnl_log_packet(), ct is only set when CONFIG_NF_CONNTRACK
> is enabled. ct's later use in __build_packet_message() is only
> meaningful when CONFIG_NF_CONNTRACK is enabled, so add a check.
> 
> In nfqnl_build_packet_message(), ct and ctinfo are only set when
> CONFIG_NF_CONNTRACK is enabled.  Add a check for their decl and use.
> 
> nfqnl_ct_parse() is a static function, move the check to the whole
> function.
> 
> In nfqa_parse_bridge(), ct and ctinfo are only set by the only
> call to nfqnl_ct_parse(), so add a check for their decl and use.
> 
> Consistently initialize ctinfo to 0.

Are compile warning being trigger without this patch, maybe with
CONFIG_NF_CONNTRACK=n?

> Signed-off-by: Tom Rix <[email-masked]>
> ---
>  net/netfilter/nfnetlink_log.c   |  4 +++-
>  net/netfilter/nfnetlink_queue.c | 18 +++++++++++++-----
>  2 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
> index ae9c0756bba59..e79d152184b71 100644
> --- a/net/netfilter/nfnetlink_log.c
> +++ b/net/netfilter/nfnetlink_log.c
> @@ -627,9 +627,11 @@ __build_packet_message(struct nfnl_log_net *log,
>  			 htonl(atomic_inc_return(&log->global_seq))))
>  		goto nla_put_failure;
>  
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  	if (ct && nfnl_ct->build(inst->skb, ct, ctinfo,
>  				 NFULA_CT, NFULA_CT_INFO) < 0)
>  		goto nla_put_failure;
> +#endif
>  
>  	if ((pf == NFPROTO_NETDEV || pf == NFPROTO_BRIDGE) &&
>  	    nfulnl_put_bridge(inst, skb) < 0)
> @@ -689,7 +691,7 @@ nfulnl_log_packet(struct net *net,
>  	struct nfnl_log_net *log = nfnl_log_pernet(net);
>  	const struct nfnl_ct_hook *nfnl_ct = NULL;
>  	struct nf_conn *ct = NULL;
> -	enum ip_conntrack_info ctinfo;
> +	enum ip_conntrack_info ctinfo = 0;
>  
>  	if (li_user && li_user->type == NF_LOG_TYPE_ULOG)
>  		li = li_user;
> diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
> index 44c3de176d186..d59cae7561bf8 100644
> --- a/net/netfilter/nfnetlink_queue.c
> +++ b/net/netfilter/nfnetlink_queue.c
> @@ -386,8 +386,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
>  	struct sk_buff *entskb = entry->skb;
>  	struct net_device *indev;
>  	struct net_device *outdev;
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  	struct nf_conn *ct = NULL;
>  	enum ip_conntrack_info ctinfo = 0;
> +#endif
>  	struct nfnl_ct_hook *nfnl_ct;
>  	bool csum_verify;
>  	char *secdata = NULL;
> @@ -595,8 +597,10 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
>  	if (seclen && nla_put(skb, NFQA_SECCTX, seclen, secdata))
>  		goto nla_put_failure;
>  
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  	if (ct && nfnl_ct->build(skb, ct, ctinfo, NFQA_CT, NFQA_CT_INFO) < 0)
>  		goto nla_put_failure;
> +#endif
>  
>  	if (cap_len > data_len &&
>  	    nla_put_be32(skb, NFQA_CAP_LEN, htonl(cap_len)))
> @@ -1104,13 +1108,13 @@ static int nfqnl_recv_verdict_batch(struct sk_buff *skb,
>  	return 0;
>  }
>  
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  static struct nf_conn *nfqnl_ct_parse(struct nfnl_ct_hook *nfnl_ct,
>  				      const struct nlmsghdr *nlh,
>  				      const struct nlattr * const nfqa[],
>  				      struct nf_queue_entry *entry,
>  				      enum ip_conntrack_info *ctinfo)
>  {
> -#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  	struct nf_conn *ct;
>  
>  	ct = nf_ct_get(entry->skb, ctinfo);
> @@ -1125,10 +1129,8 @@ static struct nf_conn *nfqnl_ct_parse(struct nfnl_ct_hook *nfnl_ct,
>  				      NETLINK_CB(entry->skb).portid,
>  				      nlmsg_report(nlh));
>  	return ct;
> -#else
> -	return NULL;
> -#endif
>  }
> +#endif
>  
>  static int nfqa_parse_bridge(struct nf_queue_entry *entry,
>  			     const struct nlattr * const nfqa[])
> @@ -1172,11 +1174,13 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
>  	struct nfnl_queue_net *q = nfnl_queue_pernet(info->net);
>  	u_int16_t queue_num = ntohs(info->nfmsg->res_id);
>  	struct nfqnl_msg_verdict_hdr *vhdr;
> -	enum ip_conntrack_info ctinfo;
>  	struct nfqnl_instance *queue;
>  	struct nf_queue_entry *entry;
>  	struct nfnl_ct_hook *nfnl_ct;
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  	struct nf_conn *ct = NULL;
> +	enum ip_conntrack_info ctinfo = 0;
> +#endif
>  	unsigned int verdict;
>  	int err;
>  
> @@ -1198,11 +1202,13 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
>  	/* rcu lock already held from nfnl->call_rcu. */
>  	nfnl_ct = rcu_dereference(nfnl_ct_hook);
>  
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  	if (nfqa[NFQA_CT]) {
>  		if (nfnl_ct != NULL)
>  			ct = nfqnl_ct_parse(nfnl_ct, info->nlh, nfqa, entry,
>  					    &ctinfo);
>  	}
> +#endif
>  
>  	if (entry->state.pf == PF_BRIDGE) {
>  		err = nfqa_parse_bridge(entry, nfqa);
> @@ -1218,8 +1224,10 @@ static int nfqnl_recv_verdict(struct sk_buff *skb, const struct nfnl_info *info,
>  				 payload_len, entry, diff) < 0)
>  			verdict = NF_DROP;
>  
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
>  		if (ct && diff)
>  			nfnl_ct->seq_adjust(entry->skb, ct, ctinfo, diff);
> +#endif
>  	}
>  
>  	if (nfqa[NFQA_MARK])
> -- 
> 2.26.3
>