netfilter: nf_tables: Attach process info to NFT_MSG_NEWGEN notifications

This is helpful for 'nft monitor' to track which process caused a given
change to the ruleset.
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -1221,6 +1221,8 @@ enum nft_objref_attributes {
 enum nft_gen_attributes {
 	NFTA_GEN_UNSPEC,
 	NFTA_GEN_ID,
+	NFTA_GEN_PROC_PID,
+	NFTA_GEN_PROC_NAME,
 	__NFTA_GEN_MAX
 };
 #define NFTA_GEN_MAX		(__NFTA_GEN_MAX - 1)

net/netfilter/nf_tables_api.c

@@ -4657,6 +4657,7 @@ static int nf_tables_fill_gen_info(struct sk_buff *skb, struct net *net,
 {
 	struct nlmsghdr *nlh;
 	struct nfgenmsg *nfmsg;
+	char buf[TASK_COMM_LEN];
 	int event = nfnl_msg_type(NFNL_SUBSYS_NFTABLES, NFT_MSG_NEWGEN);
 
 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg), 0);
@@ -4668,7 +4669,9 @@ static int nf_tables_fill_gen_info(struct sk_buff *skb, struct net *net,
 	nfmsg->version		= NFNETLINK_V0;
 	nfmsg->res_id		= htons(net->nft.base_seq & 0xffff);
 
-	if (nla_put_be32(skb, NFTA_GEN_ID, htonl(net->nft.base_seq)))
+	if (nla_put_be32(skb, NFTA_GEN_ID, htonl(net->nft.base_seq)) ||
+	    nla_put_be32(skb, NFTA_GEN_PROC_PID, htonl(task_pid_nr(current))) ||
+	    nla_put_string(skb, NFTA_GEN_PROC_NAME, get_task_comm(buf, current)))
 		goto nla_put_failure;
 
 	nlmsg_end(skb, nlh);