kcm_tx_msg
static inline struct kcm_tx_msg *kcm_tx_msg(struct sk_buff *skb)
return (struct kcm_tx_msg *)skb->cb;
kcm_tx_msg(skb_peek(&sk->sk_write_queue))->started_tx = false;
struct kcm_tx_msg *txm = kcm_tx_msg(head);
skb = kcm_tx_msg(head)->last_skb;
kcm_tx_msg(head)->last_skb = skb;