netdev - Re: [PATCH] Revert "net: pskb_trim_rcsum() and CHECKSUM

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Date:   Sun, 17 Jun 2018 15:54:48 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Andreas Schwab <schwab@...ux-m68k.org>
Cc:     Mathieu Malaterre <malat@...ian.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Christophe LEROY <christophe.leroy@....fr>,
        Meelis Roos <mroos@...ux.ee>, netdev@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] Revert "net: pskb_trim_rcsum() and CHECKSUM_COMPLETE are
 friends"



On 06/17/2018 03:27 AM, Andreas Schwab wrote:

> 
> That doesn't change anything.

OK, thanks !

Oh this is silly, please try :

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c642304f178ce0a4e1358d59e45032a39f76fb3f..54dd9c18ecad817812898d6f335e1794a07dabbe 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1845,10 +1845,9 @@ EXPORT_SYMBOL(___pskb_trim);
 int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len)
 {
        if (skb->ip_summed == CHECKSUM_COMPLETE) {
-               int delta = skb->len - len;
+               __wsum csumdiff = skb_checksum(skb, len, skb->len - len, 0);
 
-               skb->csum = csum_sub(skb->csum,
-                                    skb_checksum(skb, len, delta, 0));
+               skb->csum = csum_block_sub(skb->csum, csumdiff, len);
        }
        return __pskb_trim(skb, len);
 }