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[52.0.43.43]) by smtp-relay.gmail.com with ESMTPS id kx3-20020a17090b228300b001dc2bd0ee43sm18281pjb.10.2022.04.29.20.40.46 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Apr 2022 20:40:47 -0700 (PDT) X-Relaying-Domain: arista.com Received: from chmeee (unknown [10.95.70.41]) by smtp.aristanetworks.com (Postfix) with ESMTPS id 7892030000A6; Fri, 29 Apr 2022 20:40:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=Arista-A; t=1651290043; bh=u6hTtfz+hORBH7Ipz/k8t7/DLjFpKm6aGAHQesdLeHg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AsLpz0UcwklCqHSBtn8EgTmsTeeB7fWgJHcjqS9/VoGz7SY6ip44EewZyAyhSUIrM bn0ogHv9Nwr9FIlwQF1LlijmYLSqousG5w67WyAoQtTKkJ3k34lbozhnLhLX3aoo69 xQR2Z8PMztdpN1G5B0MTt1eIRokh3/gQ7QmD+LMuHEK7emCpgeXY/bTqyj3FPYH6O7 Eke3/+xtKznBEVttRPrnFic971BPd0mfMKVIjygXE5IXGGh4SfcO7aXOsDSVTKQlXP BhWpOwmpsoerFTpjw7Nkla2mEVPzYMW5h1pzW6p5aC4GBDFd/89ofps8kOatvixIuV PJ3TWpcTfDpww== Received: from kevmitch by chmeee with local (Exim 4.95) (envelope-from ) id 1nkdyI-0005ZA-2r; Fri, 29 Apr 2022 20:40:38 -0700 From: Kevin Mitchell Cc: kevmitch@arista.com, gal@nvidia.com, Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Hideaki YOSHIFUJI , David Ahern , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH nf-next v3] netfilter: conntrack: skip verification of zero UDP checksum Date: Fri, 29 Apr 2022 20:40:27 -0700 Message-Id: <20220430034027.21286-1-kevmitch@arista.com> In-Reply-To: References: Content-Transfer-Encoding: 8bit To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The checksum is optional for UDP packets. However nf_reject would previously require a valid checksum to elicit a response such as ICMP_DEST_UNREACH. Add some logic to nf_reject_verify_csum to determine if a UDP packet has a zero checksum and should therefore not be verified. Signed-off-by: Kevin Mitchell --- include/net/netfilter/nf_reject.h | 21 +++++++++++++++++---- net/ipv4/netfilter/nf_reject_ipv4.c | 10 +++++++--- net/ipv6/netfilter/nf_reject_ipv6.c | 4 ++-- 3 files changed, 26 insertions(+), 9 deletions(-) diff --git a/include/net/netfilter/nf_reject.h b/include/net/netfilter/nf_reject.h index 9051c3a0c8e7..7c669792fb9c 100644 --- a/include/net/netfilter/nf_reject.h +++ b/include/net/netfilter/nf_reject.h @@ -5,12 +5,28 @@ #include #include -static inline bool nf_reject_verify_csum(__u8 proto) +static inline bool nf_reject_verify_csum(struct sk_buff *skb, int dataoff, + __u8 proto) { /* Skip protocols that don't use 16-bit one's complement checksum * of the entire payload. */ switch (proto) { + /* Protocols with optional checksums. */ + case IPPROTO_UDP: { + const struct udphdr *udp_hdr; + struct udphdr _udp_hdr; + + udp_hdr = skb_header_pointer(skb, dataoff, + sizeof(_udp_hdr), + &_udp_hdr); + if (!udp_hdr || udp_hdr->check) + return true; + + return false; + } + case IPPROTO_GRE: + /* Protocols with other integrity checks. */ case IPPROTO_AH: case IPPROTO_ESP: @@ -19,9 +35,6 @@ static inline bool nf_reject_verify_csum(__u8 proto) /* Protocols with partial checksums. */ case IPPROTO_UDPLITE: case IPPROTO_DCCP: - - /* Protocols with optional checksums. */ - case IPPROTO_GRE: return false; } return true; diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c index 4eed5afca392..6c46d4e8ab84 100644 --- a/net/ipv4/netfilter/nf_reject_ipv4.c +++ b/net/ipv4/netfilter/nf_reject_ipv4.c @@ -82,6 +82,7 @@ struct sk_buff *nf_reject_skb_v4_unreach(struct net *net, unsigned int len; __wsum csum; u8 proto; + int dataoff; if (!nf_reject_iphdr_validate(oldskb)) return NULL; @@ -99,10 +100,11 @@ struct sk_buff *nf_reject_skb_v4_unreach(struct net *net, if (pskb_trim_rcsum(oldskb, ntohs(ip_hdr(oldskb)->tot_len))) return NULL; + dataoff = ip_hdrlen(oldskb); proto = ip_hdr(oldskb)->protocol; if (!skb_csum_unnecessary(oldskb) && - nf_reject_verify_csum(proto) && + nf_reject_verify_csum(oldskb, dataoff, proto) && nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), proto)) return NULL; @@ -312,6 +314,7 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) { struct iphdr *iph = ip_hdr(skb_in); u8 proto = iph->protocol; + int dataoff = ip_hdrlen(skb_in); if (iph->frag_off & htons(IP_OFFSET)) return; @@ -320,12 +323,13 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) nf_reject_fill_skb_dst(skb_in) < 0) return; - if (skb_csum_unnecessary(skb_in) || !nf_reject_verify_csum(proto)) { + if (skb_csum_unnecessary(skb_in) || + !nf_reject_verify_csum(skb_in, dataoff, proto)) { icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); return; } - if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0) + if (nf_ip_checksum(skb_in, hook, dataoff, proto) == 0) icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); } EXPORT_SYMBOL_GPL(nf_send_unreach); diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c index dffeaaaadcde..f61d4f18e1cf 100644 --- a/net/ipv6/netfilter/nf_reject_ipv6.c +++ b/net/ipv6/netfilter/nf_reject_ipv6.c @@ -31,7 +31,7 @@ static bool nf_reject_v6_csum_ok(struct sk_buff *skb, int hook) if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) return false; - if (!nf_reject_verify_csum(proto)) + if (!nf_reject_verify_csum(skb, thoff, proto)) return true; return nf_ip6_checksum(skb, hook, thoff, proto) == 0; @@ -388,7 +388,7 @@ static bool reject6_csum_ok(struct sk_buff *skb, int hook) if (thoff < 0 || thoff >= skb->len || (fo & htons(~0x7)) != 0) return false; - if (!nf_reject_verify_csum(proto)) + if (!nf_reject_verify_csum(skb, thoff, proto)) return true; return nf_ip6_checksum(skb, hook, thoff, proto) == 0; -- 2.35.1