l2tp: Add support for zero IPv6 checksums

Added new L2TP configuration options to allow TX and RX of
zero checksums in IPv6. Default is not to use them.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 18 insertions, 2 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index a1186105f537..379558014b60 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1102,7 +1102,9 @@ static void l2tp_xmit_ipv6_csum(struct sock *sk, struct sk_buff *skb,
         struct ipv6_pinfo *np = inet6_sk(sk);
         struct udphdr *uh = udp_hdr(skb);
 
-        if (!skb_dst(skb) || !skb_dst(skb)->dev ||
+        if (udp_get_no_check6_tx(sk))
+                skb->ip_summed = CHECKSUM_NONE;
+        else if (!skb_dst(skb) || !skb_dst(skb)->dev ||
             !(skb_dst(skb)->dev->features & NETIF_F_IPV6_CSUM)) {
                 __wsum csum = skb_checksum(skb, 0, udp_len, 0);
                 skb->ip_summed = CHECKSUM_UNNECESSARY;
@@ -1435,6 +1437,11 @@ static int l2tp_tunnel_sock_create(struct net *net,
                                              sizeof(udp6_addr), 0);
                         if (err < 0)
                                 goto out;
+
+                        if (cfg->udp6_zero_tx_checksums)
+                                udp_set_no_check6_tx(sock->sk, true);
+                        if (cfg->udp6_zero_rx_checksums)
+                                udp_set_no_check6_rx(sock->sk, true);
                 } else
 #endif
                 {
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 3f93ccd6ba97..68aa9ffd4ae4 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -162,7 +162,9 @@ struct l2tp_tunnel_cfg {
 #endif
         u16                     local_udp_port;
         u16                     peer_udp_port;
-        unsigned int            use_udp_checksums:1;
+        unsigned int            use_udp_checksums:1,
+                                udp6_zero_tx_checksums:1,
+                                udp6_zero_rx_checksums:1;
 };
 
 struct l2tp_tunnel {
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index f3d331bdd706..0ac907adb2f4 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -161,6 +161,13 @@ static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info
                         cfg.peer_udp_port = nla_get_u16(info->attrs[L2TP_ATTR_UDP_DPORT]);
                 if (info->attrs[L2TP_ATTR_UDP_CSUM])
                         cfg.use_udp_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_CSUM]);
+
+#if IS_ENABLED(CONFIG_IPV6)
+                if (info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX])
+                        cfg.udp6_zero_tx_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX]);
+                if (info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX])
+                        cfg.udp6_zero_rx_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX]);
+#endif
         }
 
         if (info->attrs[L2TP_ATTR_DEBUG])