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| TCP_ECN_check_ce(tp, skb); /* 检查ECE是否设置 */
/* 以下则把数据包排队到乱序队列 */
/* 同样先判断内存是否满足 */
if (tcp_try_rmem_schedule(sk, skb->truesize))
goto drop;
/* Disable header prediction. */
tp->pred_flags = 0;
inet_csk_schedule_ack(sk);
SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X/n",
tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
skb_set_owner_r(skb, sk);
/* 该数据包是乱序队列的第一个数据包*/
if (!skb_peek(&tp->out_of_order_queue)) {
/* Initial out of order segment, build 1 SACK. */
if (tcp_is_sack(tp)) {
tp->rx_opt.num_sacks = 1;
tp->rx_opt.dsack = 0;
tp->rx_opt.eff_sacks = 1;
tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
tp->selective_acks[0].end_seq =
TCP_SKB_CB(skb)->end_seq;
}
__skb_queue_head(&tp->out_of_order_queue, skb);
} else {
struct sk_buff *skb1 = tp->out_of_order_queue.prev;
u32 seq = TCP_SKB_CB(skb)->seq;
u32 end_seq = TCP_SKB_CB(skb)->end_seq;
/*刚好与乱序队列最后一个数据包数据衔接*/
if (seq == TCP_SKB_CB(skb1)->end_seq) {
__skb_queue_after(&tp->out_of_order_queue, skb1, skb);
/*如果没有sack block或者当前数据包开始序号不等于第一个block右边界*/
if (!tp->rx_opt.num_sacks ||
tp->selective_acks[0].end_seq != seq)
goto add_sack;
/*该数据包在某个hole后是按序到达的，所以可以直接扩展第一个sack*/
/* Common case: data arrive in order after hole. */
tp->selective_acks[0].end_seq = end_seq;
return;
}
/* Find place to insert this segment. */
/* 该循环找到一个开始序号不大于该数据包开始序号的乱序队列中的数据包*/
do {
if (!after(TCP_SKB_CB(skb1)->seq, seq))
break;
} while ((skb1 = skb1->prev) !=
(struct sk_buff *)&tp->out_of_order_queue);
/* Do skb overlap to previous one? 检查与前个数据包是否有重叠*/
if (skb1 != (struct sk_buff *)&tp->out_of_order_queue &&
before(seq, TCP_SKB_CB(skb1)->end_seq)) {
if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
/* All the bits are present. Drop. */
__kfree_skb(skb);
tcp_dsack_set(sk, seq, end_seq);
goto add_sack;
}
if (after(seq, TCP_SKB_CB(skb1)->seq)) {
/* Partial overlap. */
tcp_dsack_set(sk, seq,
TCP_SKB_CB(skb1)->end_seq);
} else {
skb1 = skb1->prev;
}
}
/* 排队到乱序队列*/
__skb_queue_after(&tp->out_of_order_queue, skb1, skb);
/* And clean segments covered by new one as whole. 检测与后面的数据包重叠*/
while ((skb1 = skb->next) !=
(struct sk_buff *)&tp->out_of_order_queue &&
after(end_seq, TCP_SKB_CB(skb1)->seq)) {
if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
end_seq);
break;
}
__skb_unlink(skb1, &tp->out_of_order_queue);
tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
TCP_SKB_CB(skb1)->end_seq);
__kfree_skb(skb1);
}
add_sack:
if (tcp_is_sack(tp))
/* 根据乱序队列的现状更新SACK的blocks */
tcp_sack_new_ofo_skb(sk, seq, end_seq);
}
}
|
