何时调用tcp_any_retrans_done或该函数的意图是什么

goingstudy

哪位大哥能帮忙解释一下这个函数的用意是什么，代码里有很大的一段注释，但是感觉还是不很明白。说真的，虽然kernel说20%的是注释，但是感觉那些注释都写的不是很好懂

1. /* Undo procedures. */
   
2. 
   
3. /* We can clear retrans_stamp when there are no retransmissions in the
   
4. * window. It would seem that it is trivially available for us in
   
5. * tp->retrans_out, however, that kind of assumptions doesn't consider
   
6. * what will happen if errors occur when sending retransmission for the
   
7. * second time. ...It could the that such segment has only
   
8. * TCPCB_EVER_RETRANS set at the present time. It seems that checking
   
9. * the head skb is enough except for some reneging corner cases that
   
10. * are not worth the effort.
    
11. *
    
12. * Main reason for all this complexity is the fact that connection dying
    
13. * time now depends on the validity of the retrans_stamp, in particular,
    
14. * that successive retransmissions of a segment must not advance
    
15. * retrans_stamp under any conditions.
    
16. */
    
17. static bool tcp_any_retrans_done(const struct sock *sk)
    
18. {
    
19.     const struct tcp_sock *tp = tcp_sk(sk);
    
20.     struct sk_buff *skb;
    
21. 
    
22.     if (tp->retrans_out)
    
23.         return true;
    
24. 
    
25.     skb = tcp_write_queue_head(sk);
    
26.     if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS))
    
27.         return true;
    
28. 
    
29.     return false;
    
30. }
    

复制代码

goingstudy

人工置顶。。。。

qianguozheng

判断重传是否完成吧