netdev - [PATCH net 2/3] udp: check encap socket in __udp_lib

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Message-Id: <20210712005554.26948-3-vfedorenko@novek.ru>
Date:   Mon, 12 Jul 2021 03:55:53 +0300
From:   Vadim Fedorenko <vfedorenko@...ek.ru>
To:     David Ahern <dsahern@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Xin Long <lucien.xin@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Vadim Fedorenko <vfedorenko@...ek.ru>
Subject: [PATCH net 2/3] udp: check encap socket in __udp_lib_err

Commit d26796ae5894 ("udp: check udp sock encap_type in __udp_lib_err")
added checks for encapsulated sockets but it broke cases when there is
no implementation of encap_err_lookup for encapsulation, i.e. ESP in
UDP encapsulation. Fix it by calling encap_err_lookup only if socket
implements this method otherwise treat it as legal socket.

Fixes: d26796ae5894 ("udp: check udp sock encap_type in __udp_lib_err")
Signed-off-by: Vadim Fedorenko <vfedorenko@...ek.ru>
---
 net/ipv4/udp.c | 24 +++++++++++++++++++++++-
 net/ipv6/udp.c | 22 ++++++++++++++++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index e5cb7fedfbcd..4980e0f19990 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -707,7 +707,29 @@ int __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
 	sk = __udp4_lib_lookup(net, iph->daddr, uh->dest,
 			       iph->saddr, uh->source, skb->dev->ifindex,
 			       inet_sdif(skb), udptable, NULL);
-	if (!sk || udp_sk(sk)->encap_enabled) {
+	if (sk && udp_sk(sk)->encap_enabled) {
+		int (*lookup)(struct sock *sk, struct sk_buff *skb);
+
+		lookup = READ_ONCE(udp_sk(sk)->encap_err_lookup);
+		if (lookup) {
+			int network_offset, transport_offset;
+
+			network_offset = skb_network_offset(skb);
+			transport_offset = skb_transport_offset(skb);
+
+			/* Network header needs to point to the outer IPv4 header inside ICMP */
+			skb_reset_network_header(skb);
+
+			/* Transport header needs to point to the UDP header */
+			skb_set_transport_header(skb, iph->ihl << 2);
+			if (lookup(sk, skb))
+				sk = NULL;
+			skb_set_transport_header(skb, transport_offset);
+			skb_set_network_header(skb, network_offset);
+		}
+	}
+
+	if (!sk) {
 		/* No socket for error: try tunnels before discarding */
 		sk = ERR_PTR(-ENOENT);
 		if (static_branch_unlikely(&udp_encap_needed_key)) {
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 798916d2e722..ed49a8589d9f 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -558,6 +558,28 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 
 	sk = __udp6_lib_lookup(net, daddr, uh->dest, saddr, uh->source,
 			       inet6_iif(skb), inet6_sdif(skb), udptable, NULL);
+	if (sk && udp_sk(sk)->encap_enabled) {
+		int (*lookup)(struct sock *sk, struct sk_buff *skb);
+
+		lookup = READ_ONCE(udp_sk(sk)->encap_err_lookup);
+		if (lookup) {
+			int network_offset, transport_offset;
+
+			network_offset = skb_network_offset(skb);
+			transport_offset = skb_transport_offset(skb);
+
+			/* Network header needs to point to the outer IPv6 header inside ICMP */
+			skb_reset_network_header(skb);
+
+			/* Transport header needs to point to the UDP header */
+			skb_set_transport_header(skb, offset);
+			if (lookup(sk, skb))
+				sk = NULL;
+			skb_set_transport_header(skb, transport_offset);
+			skb_set_network_header(skb, network_offset);
+		}
+	}
+
 	if (!sk || udp_sk(sk)->encap_enabled) {
 		/* No socket for error: try tunnels before discarding */
 		sk = ERR_PTR(-ENOENT);
-- 
2.18.4