(OK)(OK) Android-x86-7.1.1/ kernel 4.4.62

gedit kernel/net/mptcp/mptcp_output.c

bool mptcp_write_xmit(struct sock *meta_sk, unsigned int mss_now, int nonagle,     int push_one, gfp_t gfp){struct tcp_sock *meta_tp = tcp_sk(meta_sk), *subtp;struct sock *subsk = NULL;struct mptcp_cb *mpcb = meta_tp->mpcb;struct sk_buff *skb;int reinject = 0;unsigned int sublimit;__u32 path_mask = 0;//ztg addprintk(KERN_INFO "mptcp: mptcp_write_xmit: 1111\n");while ((skb = mpcb->sched_ops->next_segment(meta_sk, &reinject, &subsk,    &sublimit))) {unsigned int limit;WARN(TCP_SKB_CB(skb)->sacked, "sacked: %u reinject: %u",     TCP_SKB_CB(skb)->sacked, reinject);//ztg addprintk(KERN_INFO "mptcp: mptcp_write_xmit: 2222\n");subtp = tcp_sk(subsk);mss_now = tcp_current_mss(subsk);if (reinject == 1) {if (!after(TCP_SKB_CB(skb)->end_seq, meta_tp->snd_una)) {/* Segment already reached the peer, take the next one */__skb_unlink(skb, &mpcb->reinject_queue);__kfree_skb(skb);continue;}}/* If the segment was cloned (e.g. a meta retransmission), * the header must be expanded/copied so that there is no * corruption of TSO information. */if (skb_unclone(skb, GFP_ATOMIC))break;if (unlikely(!tcp_snd_wnd_test(meta_tp, skb, mss_now)))break;/* Force tso_segs to 1 by using UINT_MAX. * We actually don't care about the exact number of segments * emitted on the subflow. We need just to set tso_segs, because * we still need an accurate packets_out count in * tcp_event_new_data_sent. */tcp_set_skb_tso_segs(skb, UINT_MAX);/* Check for nagle, irregardless of tso_segs. If the segment is * actually larger than mss_now (TSO segment), then * tcp_nagle_check will have partial == false and always trigger * the transmission. * tcp_write_xmit has a TSO-level nagle check which is not * subject to the MPTCP-level. It is based on the properties of * the subflow, not the MPTCP-level. */if (unlikely(!tcp_nagle_test(meta_tp, skb, mss_now,     (tcp_skb_is_last(meta_sk, skb) ?      nonagle : TCP_NAGLE_PUSH))))break;limit = mss_now;/* skb->len > mss_now is the equivalent of tso_segs > 1 in * tcp_write_xmit. Otherwise split-point would return 0. */if (skb->len > mss_now && !tcp_urg_mode(meta_tp))/* We limit the size of the skb so that it fits into the * window. Call tcp_mss_split_point to avoid duplicating * code. * We really only care about fitting the skb into the * window. That's why we use UINT_MAX. If the skb does * not fit into the cwnd_quota or the NIC's max-segs * limitation, it will be split by the subflow's * tcp_write_xmit which does the appropriate call to * tcp_mss_split_point. */limit = tcp_mss_split_point(meta_sk, skb, mss_now,    UINT_MAX / mss_now,    nonagle);if (sublimit)limit = min(limit, sublimit);if (skb->len > limit &&    unlikely(mptcp_fragment(meta_sk, skb, limit, gfp, reinject)))break;if (!mptcp_skb_entail(subsk, skb, reinject))break;/* Nagle is handled at the MPTCP-layer, so * always push on the subflow */__tcp_push_pending_frames(subsk, mss_now, TCP_NAGLE_PUSH);meta_tp->lsndtime = tcp_time_stamp;//ztg addprintk(KERN_INFO "mptcp: mptcp_write_xmit: 3333\n");path_mask |= mptcp_pi_to_flag(subtp->mptcp->path_index);skb_mstamp_get(&skb->skb_mstamp);if (!reinject) {mptcp_check_sndseq_wrap(meta_tp,TCP_SKB_CB(skb)->end_seq -TCP_SKB_CB(skb)->seq);tcp_event_new_data_sent(meta_sk, skb);}tcp_minshall_update(meta_tp, mss_now, skb);if (reinject > 0) {__skb_unlink(skb, &mpcb->reinject_queue);kfree_skb(skb);}if (push_one)break;}mptcp_for_each_sk(mpcb, subsk) {subtp = tcp_sk(subsk);//ztg add//----------------------------------------------------------------------printk(KERN_INFO "mptcp: mptcp_write_xmit: 4444\n");printk(KERN_INFO "mptcp: mptcp_write_xmit: src_addr:%pI4:%d dst_addr:%pI4:%d, cnt_subflows now %d\n",    &((struct inet_sock *)tcp_sk(subsk))->inet_saddr,    ntohs(((struct inet_sock *)tcp_sk(subsk))->inet_sport),    &((struct inet_sock *)tcp_sk(subsk))->inet_daddr,    ntohs(((struct inet_sock *)tcp_sk(subsk))->inet_dport),    tcp_sk(meta_sk)->mpcb->cnt_subflows);//----------------------------------------------------------------------if (!(path_mask & mptcp_pi_to_flag(subtp->mptcp->path_index)))continue;/* We have pushed data on this subflow. We ignore the call to * cwnd_validate in tcp_write_xmit as is_cwnd_limited will never * be true (we never push more than what the cwnd can accept). * We need to ensure that we call tcp_cwnd_validate with * is_cwnd_limited set to true if we have filled the cwnd. */tcp_cwnd_validate(subsk, tcp_packets_in_flight(subtp) >=  subtp->snd_cwnd);}return !meta_tp->packets_out && tcp_send_head(meta_sk);}

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四种测试情况，具体结果 看下图

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# eth0, eth1
# "Default" "Round-Robin" "Redundant"
# 流量均衡走 eth0 & eth1, 不能够完整的传输文件 (缺少 +300 Bytes)，mptcp_write_xmit() 被调用 1 次

# eth0, eth1
# "Round-Robin" "Redundant" "Default"
# 流量均衡走 eth0 & eth1, 不能够完整的传输文件 (缺少 +300 Bytes)，mptcp_write_xmit() 被调用 1 次

# eth0, eth1, eth2 (dhcp)
# "Default" "Round-Robin" "Redundant"
# 流量主要走 eth2 (dhcp), 能够完整的传输文件，mptcp_write_xmit() 被调用 1 次

# eth0, eth1, eth2 (dhcp)
# "Round-Robin" "Redundant" "Default"
# 流量主要走 eth2 (dhcp), 能够完整的传输文件，mptcp_write_xmit() 被调用 5 次 或 3 次 (每次测试，调用的次数不一样)

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# eth0, eth1
# "Default" "Round-Robin" "Redundant"
# 流量均衡走 eth0 & eth1, 不能够完整的传输文件 (缺少 +300 Bytes)，mptcp_write_xmit() 被调用 1 次

更详细的输出

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# eth0, eth1

# "Round-Robin" "Redundant" "Default"
# 流量均衡走 eth0 & eth1, 不能够完整的传输文件 (缺少 +300 Bytes)，mptcp_write_xmit() 被调用 1 次

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# eth0, eth1, eth2 (dhcp)
# "Default" "Round-Robin" "Redundant"
# 流量主要走 eth2 (dhcp), 能够完整的传输文件，mptcp_write_xmit() 被调用 1 次

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# eth0, eth1, eth2 (dhcp)

# "Round-Robin" "Redundant" "Default"
# 流量主要走 eth2 (dhcp), 能够完整的传输文件，mptcp_write_xmit() 被调用 5 次