sk_forward_alloc_add
sk_forward_alloc_add(sk, -size);
sk_forward_alloc_add(sk, size);
sk_forward_alloc_add(sk, pages << PAGE_SHIFT);
sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
sk_forward_alloc_add(sk, -(amt << PAGE_SHIFT));
sk_forward_alloc_add(sk, -(amount << PAGE_SHIFT));
sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
sk_forward_alloc_add(sk, size - amt);
sk_forward_alloc_add(sk, -size);
sk_forward_alloc_add(sk, -total_ts);
sk_forward_alloc_add(sk, fwd_remaining);
sk_forward_alloc_add(ssk, -fwd_remaining);
sk_forward_alloc_add(sk, skb->truesize);