seg6: Cleanup duplicates of skb_dst_drop calls

In processing IPv6 segment routing header (SRH), several functions call
skb_dst_drop before ip6_route_input. However, ip6_route_input calls
skb_dst_drop within it, so there is no need to call skb_dst_drop in advance.

Signed-off-by: Yuya Tajima <yuya.tajimaa@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Yuya9786

net/ipv6/exthdrs.c

@@ -458,8 +458,6 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 
 	ipv6_hdr(skb)->daddr = *addr;
 
-	skb_dst_drop(skb);
-
 	ip6_route_input(skb);
 
 	if (skb_dst(skb)->error) {
@@ -834,7 +832,6 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	*addr = ipv6_hdr(skb)->daddr;
 	ipv6_hdr(skb)->daddr = daddr;
 
-	skb_dst_drop(skb);
 	ip6_route_input(skb);
 	if (skb_dst(skb)->error) {
 		skb_push(skb, skb->data - skb_network_header(skb));

net/ipv6/seg6_iptunnel.c

@@ -470,8 +470,6 @@ static int seg6_input_core(struct net *net, struct sock *sk,
 	dst = dst_cache_get(&slwt->cache);
 	preempt_enable();
 
-	skb_dst_drop(skb);
-
 	if (!dst) {
 		ip6_route_input(skb);
 		dst = skb_dst(skb);
@@ -482,6 +480,7 @@ static int seg6_input_core(struct net *net, struct sock *sk,
 			preempt_enable();
 		}
 	} else {
+		skb_dst_drop(skb);
 		skb_dst_set(skb, dst);
 	}