From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [91.216.245.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E08144E673 for ; Mon, 14 Sep 2026 16:59:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.216.245.30 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789405153; cv=none; b=FyZ8V2kU3jQZaGXvT8LbhZ46wKpQE/ig+VJBAKRY5PLqQSautSwm1mql65qgcA2+csvIXdXKIhj9Uuuu8yPlPD4lng8nvWsAqZi7Ob8rIcoGpZnoSUL81HD5h/NnykC6lkz5oYlFbZ9sRpapTPPDarINh2fKBFT2qGfspyD0E+c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789405153; c=relaxed/simple; bh=BSpiGGP1C9WJcIYYKpOmPtqsuTBU8AB5Eh5rWFu/kmA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BLCK25N34S3FO6oS23iVE/rwXg2b3ZLKw5kerObkSdNXowG/PI25K9+LOvDXDZUBLuNzfGHtMYCGG6zYAo7qa/Q+HKuTjxbvjdVkCCEj8chEXYaYULrd+m6qoPAg9GMV9w2ArnVQPfX7MM2TvlED/me0OAHNAzyHzlnQ70R9ElM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de; spf=pass smtp.mailfrom=Chamillionaire.breakpoint.cc; arc=none smtp.client-ip=91.216.245.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=Chamillionaire.breakpoint.cc Received: by Chamillionaire.breakpoint.cc (Postfix, from userid 1003) id E4C7760468; Mon, 14 Sep 2026 18:59:08 +0200 (CEST) From: Florian Westphal To: Cc: Florian Westphal Subject: [PATCH nf 2/6] netfilter: nf_conntrack: refactor helper call logic in nf_confirm() Date: Mon, 14 Sep 2026 18:58:38 +0200 Message-ID: <20260914165842.4505-3-fw@strlen.de> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260914165842.4505-2-fw@strlen.de> References: <20260914165842.4505-2-fw@strlen.de> Precedence: bulk X-Mailing-List: netfilter-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The current implementation of nf_confirm() handles several distinct tasks: retrieving the connection, calculating protocol offsets for different network families, and executing the associated helpers or sequence adjustments. Move functionality to extra functions: 1. nf_confirm_get_protoff(): Isolates the logic for determining the protocol offset (protoff) for IPv4 and IPv6 packets. 2. nf_ct_call_helper(): Encapsulates the decision-making process of whether to call a connection tracking helper or perform sequence adjustment, utilizing nf_confirm_get_protoff() to find the correct offset. NF_CT_STAT_INC_ATOMIC() is now incremented for any NF_DROP, earlier this was elided in some cases, IMO that was a bug all along. Followup patches will extend these new functions with stricter checks. Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.") Signed-off-by: Florian Westphal --- include/net/netfilter/nf_conntrack_helper.h | 2 + net/netfilter/nf_conntrack_proto.c | 113 +++++++++++++++----- 2 files changed, 87 insertions(+), 28 deletions(-) diff --git a/include/net/netfilter/nf_conntrack_helper.h b/include/net/netfilter/nf_conntrack_helper.h index 335b8c43694f..4b5ee758cff3 100644 --- a/include/net/netfilter/nf_conntrack_helper.h +++ b/include/net/netfilter/nf_conntrack_helper.h @@ -124,6 +124,8 @@ int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl, int nf_ct_helper(struct sk_buff *skb, struct nf_conn *ct, enum ip_conntrack_info ctinfo, u16 proto); +int nf_ct_call_helper(struct sk_buff *skb, struct nf_conn *ct, + enum ip_conntrack_info ctinfo); int nf_ct_add_helper(struct nf_conn *ct, const char *name, u8 family, u8 proto, bool nat, struct nf_conntrack_helper **hp); diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c index 7a40e4e0e33e..32f900c155de 100644 --- a/net/netfilter/nf_conntrack_proto.c +++ b/net/netfilter/nf_conntrack_proto.c @@ -131,36 +131,16 @@ static bool in_vrf_postrouting(const struct nf_hook_state *state) return false; } -unsigned int nf_confirm(void *priv, - struct sk_buff *skb, - const struct nf_hook_state *state) +static bool nf_confirm_get_protoff(struct sk_buff *skb, struct net *net, + struct nf_conn *ct, + enum ip_conntrack_info ctinfo, + unsigned int *protoffp) { - int (*helper_cb)(struct sk_buff *skb, unsigned int protoff, - struct nf_conn *ct, - enum ip_conntrack_info conntrackinfo); - const struct nf_conn_help *help; - enum ip_conntrack_info ctinfo; unsigned int protoff; - struct nf_conn *ct; - bool seqadj_needed; __be16 frag_off; int start; u8 pnum; - ct = nf_ct_get(skb, &ctinfo); - if (!ct || in_vrf_postrouting(state)) - return NF_ACCEPT; - - help = nfct_help(ct); - - seqadj_needed = test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) && !nf_is_loopback_packet(skb); - if (!help && !seqadj_needed) - return nf_conntrack_confirm(skb); - - /* helper->help() do not expect ICMP packets */ - if (ctinfo == IP_CT_RELATED_REPLY) - return nf_conntrack_confirm(skb); - switch (nf_ct_l3num(ct)) { case NFPROTO_IPV4: protoff = skb_network_offset(skb) + ip_hdrlen(skb); @@ -169,16 +149,56 @@ unsigned int nf_confirm(void *priv, pnum = ipv6_hdr(skb)->nexthdr; start = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &pnum, &frag_off); if (start < 0 || (frag_off & htons(~0x7)) != 0) - return nf_conntrack_confirm(skb); + return false; protoff = start; break; default: - return nf_conntrack_confirm(skb); + DEBUG_NET_WARN_ONCE(1, "helper invoked on non-IP family!"); + return false; } + *protoffp = protoff; + return true; +} + +/** + * nf_ct_call_helper() - Invoke the connection tracking helper for a packet + * @skb: The socket buffer containing the packet to be processed. + * @ct: The connection tracking entry associated with this packet. + * @ctinfo: The current connection track information (state) of the packet. + * + * This function calls the l4 connection tracking helper (e.g. ftp, sip...) if + * one was assigned to the connection. + * + * Return: verdict (NF_ACCEPT, NF_DROP, ...) + */ +int nf_ct_call_helper(struct sk_buff *skb, struct nf_conn *ct, + enum ip_conntrack_info ctinfo) +{ + struct net *net = nf_ct_net(ct); + const struct nf_conn_help *help; + bool seqadj_needed; + unsigned int protoff; + + help = nfct_help(ct); + + seqadj_needed = test_bit(IPS_SEQ_ADJUST_BIT, &ct->status) && !nf_is_loopback_packet(skb); + if (!help && !seqadj_needed) + return NF_ACCEPT; + + /* helper->help() do not expect ICMP packets */ + if (ctinfo == IP_CT_RELATED_REPLY) + return NF_ACCEPT; + + if (!nf_confirm_get_protoff(skb, net, ct, ctinfo, &protoff)) + return NF_ACCEPT; + if (help) { const struct nf_conntrack_helper *helper; + int (*helper_cb)(struct sk_buff *skb, unsigned int protoff, + struct nf_conn *ct, + enum ip_conntrack_info conntrackinfo); int ret; /* rcu_read_lock()ed by nf_hook */ @@ -195,9 +215,46 @@ unsigned int nf_confirm(void *priv, } if (seqadj_needed && - !nf_ct_seq_adjust(skb, ct, ctinfo, protoff)) { - NF_CT_STAT_INC_ATOMIC(nf_ct_net(ct), drop); + !nf_ct_seq_adjust(skb, ct, ctinfo, protoff)) return NF_DROP; + + return NF_ACCEPT; +} + +/** + * nf_confirm - Confirm (commit) a connection tracking entry + * @priv: Private data from the netfilter hook registration (unused) + * @skb: Packet + * @state: Netfilter hook state containing context (netns, hooknum, in/out devices) + * + * This function is invoked as the final step of the connection tracking + * processing pipeline. It performs two main operations: + * + * 1. Invokes the associated conntrack helper (if registered) to allow + * layer 7 specific parsing and NAT mangling. + * + * 2. Commits a new conntrack entry to the conntrack hash table, making it + * globally visible and enabling future packet lookups for stateful tracking. + * + * Returns: A netfilter verdict, e.g. NF_ACCEPT or NF_DROP. + */ +unsigned int nf_confirm(void *priv, + struct sk_buff *skb, + const struct nf_hook_state *state) +{ + enum ip_conntrack_info ctinfo; + struct nf_conn *ct; + int ret; + + ct = nf_ct_get(skb, &ctinfo); + if (!ct || in_vrf_postrouting(state)) + return NF_ACCEPT; + + ret = nf_ct_call_helper(skb, ct, ctinfo); + if (unlikely(ret != NF_ACCEPT)) { + if (ret == NF_DROP) + NF_CT_STAT_INC_ATOMIC(state->net, drop); + return ret; } /* We've seen it coming out the other side: confirm it */ -- 2.55.0