netfilter: nf_tables: extend tracing infrastructure

nft monitor mode can then decode and display this trace data.

Parts of LL/Network/Transport headers are provided as separate
attributes.

Otherwise, printing IP address data becomes virtually impossible
for userspace since in the case of the netdev family we really don't
want userspace to have to know all the possible link layer types
and/or sizes just to display/print an ip address.

We also don't want userspace to have to follow ipv6 header chains
to get the s/dport info, the kernel already did this work for us.

To avoid bloating nft_do_chain all data required for tracing is
encapsulated in nft_traceinfo.

The structure is initialized unconditionally(!) for each nft_do_chain
invocation.

This unconditionall call will be moved under a static key in a
followup patch.

With lots of help from Patrick McHardy and Pablo Neira.

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 101d7d7ec243..b313cda49194 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -888,6 +888,38 @@ void nft_unregister_chain_type(const struct nf_chain_type *);
 int nft_register_expr(struct nft_expr_type *);
 void nft_unregister_expr(struct nft_expr_type *);
 
+int nft_verdict_dump(struct sk_buff *skb, int type,
+		     const struct nft_verdict *v);
+
+/**
+ *	struct nft_traceinfo - nft tracing information and state
+ *
+ *	@pkt: pktinfo currently processed
+ *	@basechain: base chain currently processed
+ *	@chain: chain currently processed
+ *	@rule:  rule that was evaluated
+ *	@verdict: verdict given by rule
+ *	@type: event type (enum nft_trace_types)
+ *	@packet_dumped: packet headers sent in a previous traceinfo message
+ *	@trace: other struct members are initialised
+ */
+struct nft_traceinfo {
+	const struct nft_pktinfo	*pkt;
+	const struct nft_base_chain	*basechain;
+	const struct nft_chain		*chain;
+	const struct nft_rule		*rule;
+	const struct nft_verdict	*verdict;
+	enum nft_trace_types		type;
+	bool				packet_dumped;
+	bool				trace;
+};
+
+void nft_trace_init(struct nft_traceinfo *info, const struct nft_pktinfo *pkt,
+		    const struct nft_verdict *verdict,
+		    const struct nft_chain *basechain);
+
+void nft_trace_notify(struct nft_traceinfo *info);
+
 #define nft_dereference(p)					\
 	nfnl_dereference(p, NFNL_SUBSYS_NFTABLES)