From: Heiner Kallweit <hkallweit1@gmail.com>
Date: Tue, 18 Feb 2020 20:56:41 +0100
Subject: net: core: add helper tcp_v6_gso_csum_prep
Patch-mainline: v5.7-rc1
Git-commit: 76eeb12b71a4aa5654694765c8c1bde9a1ce8bd8
References: jsc#SLE-13532

Several network drivers for chips that support TSO6 share the same code
for preparing the TCP header, so let's factor it out to a helper.
A difference is that some drivers reset the payload_len whilst others
don't do this. This value is overwritten by TSO anyway, therefore
the new helper resets it in general.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/net/ip6_checksum.h |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/include/net/ip6_checksum.h
+++ b/include/net/ip6_checksum.h
@@ -76,6 +76,15 @@ static inline void __tcp_v6_send_check(s
 	}
 }
 
+static inline void tcp_v6_gso_csum_prep(struct sk_buff *skb)
+{
+	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+	struct tcphdr *th = tcp_hdr(skb);
+
+	ipv6h->payload_len = 0;
+	th->check = ~tcp_v6_check(0, &ipv6h->saddr, &ipv6h->daddr, 0);
+}
+
 #if IS_ENABLED(CONFIG_IPV6)
 static inline void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb)
 {