netdev - [PATCHv2 net-next 03/17] udp: do checksum properly in skb_udp_tunnel

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Message-Id: <483d9eec159b22172fe04dacd58d7f88dfc2f301.1602150362.git.lucien.xin@gmail.com>
Date:   Thu,  8 Oct 2020 17:47:59 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Michael Tuexen <tuexen@...muenster.de>, davem@...emloft.net
Subject: [PATCHv2 net-next 03/17] udp: do checksum properly in skb_udp_tunnel_segment

This patch fixes two things:

  When skb->ip_summed == CHECKSUM_PARTIAL, skb_checksum_help() should be
  called do the checksum, instead of gso_make_checksum(), which is used
  to do the checksum for current proto after calling skb_segment(), not
  after the inner proto's gso_segment().

  When offload_csum is disabled, the hardware will not do the checksum
  for the current proto, udp. So instead of calling gso_make_checksum(),
  it should calculate checksum for udp itself.

Cc: Tom Herbert <tom@...bertland.com>
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/ipv4/udp_offload.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index e67a66f..c0b010b 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -131,14 +131,15 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 		uh->check = ~csum_fold(csum_add(partial,
 				       (__force __wsum)htonl(len)));
 
-		if (skb->encapsulation || !offload_csum) {
-			uh->check = gso_make_checksum(skb, ~uh->check);
-			if (uh->check == 0)
-				uh->check = CSUM_MANGLED_0;
-		} else {
+		if (skb->encapsulation)
+			skb_checksum_help(skb);
+
+		if (offload_csum) {
 			skb->ip_summed = CHECKSUM_PARTIAL;
 			skb->csum_start = skb_transport_header(skb) - skb->head;
 			skb->csum_offset = offsetof(struct udphdr, check);
+		} else {
+			uh->check = csum_fold(skb_checksum(skb, udp_offset, len, 0));
 		}
 	} while ((skb = skb->next));
 out:
-- 
2.1.0