[PATCH net-next 5/7] netfilter: make nftables drops visible in net dropmonitor
From: Florian Westphal <fw@strlen.de>
Date: 2023-10-18 08:51:49
Also in:
netfilter-devel
Subsystem:
netfilter, networking [general], the rest · Maintainers:
Pablo Neira Ayuso, Florian Westphal, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
net_dropmonitor blames core.c:nf_hook_slow. Add NF_DROP_REASON() helper and use it in nft_do_chain(). The helper releases the skb, so exact drop location becomes available. Calling code will observe the NF_STOLEN verdict instead. Adjust nf_hook_slow so we can embed an erro value wih NF_STOLEN verdicts, just like we do for NF_DROP. After this, drop in nftables can be pinpointed to a drop due to a rule or the chain policy. Signed-off-by: Florian Westphal <fw@strlen.de> --- include/linux/netfilter.h | 10 ++++++++++ net/netfilter/core.c | 6 +++--- net/netfilter/nf_tables_core.c | 6 +++++- 3 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index d68644b7c299..80900d910992 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h@@ -22,6 +22,16 @@ static inline int NF_DROP_GETERR(int verdict) return -(verdict >> NF_VERDICT_QBITS); } +static __always_inline int +NF_DROP_REASON(struct sk_buff *skb, enum skb_drop_reason reason, u32 err) +{ + BUILD_BUG_ON(err > 0xffff); + + kfree_skb_reason(skb, reason); + + return ((err << 16) | NF_STOLEN); +} + static inline int nf_inet_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *a2) {
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index ef4e76e5aef9..3126911f5042 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c@@ -639,10 +639,10 @@ int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state, if (ret == 1) continue; return ret; + case NF_STOLEN: + return NF_DROP_GETERR(verdict); default: - /* Implicit handling for NF_STOLEN, as well as any other - * non conventional verdicts. - */ + WARN_ON_ONCE(1); return 0; } }
diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index 6009b423f60a..8b536d7ef6c2 100644
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c@@ -308,10 +308,11 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv) switch (regs.verdict.code & NF_VERDICT_MASK) { case NF_ACCEPT: - case NF_DROP: case NF_QUEUE: case NF_STOLEN: return regs.verdict.code; + case NF_DROP: + return NF_DROP_REASON(pkt->skb, SKB_DROP_REASON_NETFILTER_DROP, EPERM); } switch (regs.verdict.code) {
@@ -342,6 +343,9 @@ nft_do_chain(struct nft_pktinfo *pkt, void *priv) if (static_branch_unlikely(&nft_counters_enabled)) nft_update_chain_stats(basechain, pkt); + if (nft_base_chain(basechain)->policy == NF_DROP) + return NF_DROP_REASON(pkt->skb, SKB_DROP_REASON_NETFILTER_DROP, EPERM); + return nft_base_chain(basechain)->policy; } EXPORT_SYMBOL_GPL(nft_do_chain);
--
2.41.0