[PATCH net] Revert "ipv6: Allow for partial checksums on non-ufo packets"

[Eric Dumazet <eric.dumazet@gmail.com>]

From: Eric Dumazet <edumazet@google.com>

Wolfgang Walter reported crashes using traceroute6, root caused to this
commit.

UDP packets can be sent from RAW sockets.

Note that the faulty commit addressed a non problem, as normal
UDP v6 packets use udp_v6_send_skb() which correctly setup
CHECKSUM_PARTIAL properly if device has the correct feature.

It seems not worth trying to 'fix' the raw path.

Fixes: 32dce968dd98 ("ipv6: Allow for partial checksums on non-ufo packets")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Wolfgang Walter <linux@stwm.de>
Cc: Vlad Yasevich <vyasevich@gmail.com>
---
 net/ipv6/ip6_output.c |   11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 7fde1f265c90..1fe5c687328e 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1218,7 +1218,6 @@ static int __ip6_append_data(struct sock *sk,
 	u32 tskey = 0;
 	struct rt6_info *rt = (struct rt6_info *)cork->dst;
 	struct ipv6_txoptions *opt = v6_cork->opt;
-	int csummode = CHECKSUM_NONE;
 
 	skb = skb_peek_tail(queue);
 	if (!skb) {
@@ -1275,14 +1274,6 @@ emsgsize:
 			tskey = sk->sk_tskey++;
 	}
 
-	/* If this is the first and only packet and device
-	 * supports checksum offloading, let's use it.
-	 */
-	if (!skb && sk->sk_protocol == IPPROTO_UDP &&
-	    length + fragheaderlen < mtu &&
-	    rt->dst.dev->features & NETIF_F_V6_CSUM &&
-	    !exthdrlen)
-		csummode = CHECKSUM_PARTIAL;
 	/*
 	 * Let's try using as much space as possible.
 	 * Use MTU if total length of the message fits into the MTU.
@@ -1396,7 +1387,7 @@ alloc_new_skb:
 			 *	Fill in the control structures
 			 */
 			skb->protocol = htons(ETH_P_IPV6);
-			skb->ip_summed = csummode;
+			skb->ip_summed = CHECKSUM_NONE;
 			skb->csum = 0;
 			/* reserve for fragmentation and ipsec header */
 			skb_reserve(skb, hh_len + sizeof(struct frag_hdr) +