Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Dongseok Yi <dseok.yi@samsung.com>
To:     "David S. Miller" <davem@davemloft.net>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        Alexander Lobakin <alobakin@pm.me>
Cc:     namkyu78.kim@samsung.com, Dongseok Yi <dseok.yi@samsung.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Willem de Bruijn <willemb@google.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH net v2] udp: ipv4: manipulate network header of NATed UDP
 GRO fraglist
Date:   Fri, 15 Jan 2021 22:20:35 +0900
Message-Id: <1610716836-140533-1-git-send-email-dseok.yi@samsung.com>
Content-Type: text/plain; charset="utf-8"
CMS-TYPE: 102P
DLP-Filter: Pass
References: <CGME20210115133200epcas2p1f52efe7bbc2826ed12da2fde4e03e3b2@epcas2p1.samsung.com>
Precedence: bulk

UDP/IP header of UDP GROed frag_skbs are not updated even after NAT
forwarding. Only the header of head_skb from ip_finish_output_gso ->
skb_gso_segment is updated but following frag_skbs are not updated.

A call path skb_mac_gso_segment -> inet_gso_segment ->
udp4_ufo_fragment -> __udp_gso_segment -> __udp_gso_segment_list
does not try to update UDP/IP header of the segment list but copy
only the MAC header.

Update dport, daddr and checksums of each skb of the segment list
in __udp_gso_segment_list. It covers both SNAT and DNAT.

Fixes: 9fd1ff5d2ac7 (udp: Support UDP fraglist GRO/GSO.)
Signed-off-by: Dongseok Yi <dseok.yi@samsung.com>
---
v1:
Steffen Klassert said, there could be 2 options.
https://lore.kernel.org/patchwork/patch/1362257/
I was trying to write a quick fix, but it was not easy to forward
segmented list. Currently, assuming DNAT only.

v2:
Per Steffen Klassert request, move the procedure from
udp4_ufo_fragment to __udp_gso_segment_list and support SNAT.

To Alexander Lobakin, I've checked your email late. Just use this
patch as a reference. It support SNAT too, but does not support IPv6
yet. I cannot make IPv6 header changes in __udp_gso_segment_list due
to the file is in IPv4 directory.

 include/net/udp.h      |  2 +-
 net/ipv4/udp_offload.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++----
 net/ipv6/udp_offload.c |  2 +-
 3 files changed, 59 insertions(+), 7 deletions(-)

diff --git a/include/net/udp.h b/include/net/udp.h
index 877832b..01351ba 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -178,7 +178,7 @@ struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
 int udp_gro_complete(struct sk_buff *skb, int nhoff, udp_lookup_t lookup);
 
 struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
-				  netdev_features_t features);
+				  netdev_features_t features, bool is_ipv6);
 
 static inline struct udphdr *udp_gro_udphdr(struct sk_buff *skb)
 {
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index ff39e94..c532d3b 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -187,8 +187,57 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
 }
 EXPORT_SYMBOL(skb_udp_tunnel_segment);
 
+static void __udpv4_gso_segment_csum(struct sk_buff *seg,
+				     __be32 *oldip, __be32 *newip,
+				     __be16 *oldport, __be16 *newport)
+{
+	struct udphdr *uh = udp_hdr(seg);
+	struct iphdr *iph = ip_hdr(seg);
+
+	if (uh->check) {
+		inet_proto_csum_replace4(&uh->check, seg, *oldip, *newip,
+					 true);
+		inet_proto_csum_replace2(&uh->check, seg, *oldport, *newport,
+					 false);
+		if (!uh->check)
+			uh->check = CSUM_MANGLED_0;
+	}
+	uh->dest = *newport;
+
+	csum_replace4(&iph->check, *oldip, *newip);
+	iph->daddr = *newip;
+}
+
+static struct sk_buff *__udpv4_gso_segment_list_csum(struct sk_buff *segs)
+{
+	struct sk_buff *seg;
+	struct udphdr *uh, *uh2;
+	struct iphdr *iph, *iph2;
+
+	seg = segs;
+	uh = udp_hdr(seg);
+	iph = ip_hdr(seg);
+
+	while ((seg = seg->next)) {
+		uh2 = udp_hdr(seg);
+		iph2 = ip_hdr(seg);
+
+		if (uh->source != uh2->source || iph->saddr != iph2->saddr)
+			__udpv4_gso_segment_csum(seg,
+						 &iph2->saddr, &iph->saddr,
+						 &uh2->source, &uh->source);
+
+		if (uh->dest != uh2->dest || iph->daddr != iph2->daddr)
+			__udpv4_gso_segment_csum(seg,
+						 &iph2->daddr, &iph->daddr,
+						 &uh2->dest, &uh->dest);
+	}
+
+	return segs;
+}
+
 static struct sk_buff *__udp_gso_segment_list(struct sk_buff *skb,
-					      netdev_features_t features)
+					      netdev_features_t features, bool is_ipv6)
 {
 	unsigned int mss = skb_shinfo(skb)->gso_size;
 
@@ -198,11 +247,14 @@ static struct sk_buff *__udp_gso_segment_list(struct sk_buff *skb,
 
 	udp_hdr(skb)->len = htons(sizeof(struct udphdr) + mss);
 
-	return skb;
+	if (is_ipv6)
+		return skb;
+	else
+		return __udpv4_gso_segment_list_csum(skb);
 }
 
 struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
-				  netdev_features_t features)
+				  netdev_features_t features, bool is_ipv6)
 {
 	struct sock *sk = gso_skb->sk;
 	unsigned int sum_truesize = 0;
@@ -214,7 +266,7 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 	__be16 newlen;
 
 	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
-		return __udp_gso_segment_list(gso_skb, features);
+		return __udp_gso_segment_list(gso_skb, features, is_ipv6);
 
 	mss = skb_shinfo(gso_skb)->gso_size;
 	if (gso_skb->len <= sizeof(*uh) + mss)
@@ -328,7 +380,7 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 		goto out;
 
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
-		return __udp_gso_segment(skb, features);
+		return __udp_gso_segment(skb, features, false);
 
 	mss = skb_shinfo(skb)->gso_size;
 	if (unlikely(skb->len <= mss))
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index c7bd7b1..faa823c 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -42,7 +42,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 			goto out;
 
 		if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
-			return __udp_gso_segment(skb, features);
+			return __udp_gso_segment(skb, features, true);
 
 		mss = skb_shinfo(skb)->gso_size;
 		if (unlikely(skb->len <= mss))
-- 
2.7.4