Man page 9 : skb_dst_set_noref

skb_dst_set_noref - sets skb dst, hopefully, without taking reference

void skb_dst_set_noref(struct sk_buff *  skb , struct dst_entry *  dst );

skb
    buffer

dst
    dst entry

Sets skb dst, assuming a reference was not taken on dst. If dst entry is cached, we do not take reference and dst_release will be avoided by refdst_drop. If dst entry is not cached, we take reference, so that last dst_release can destroy the dst immediately.