服务器调用send_bytes向客户端发数据，在满足以下两个条件时失败：

1. 客户端通过公网ip连接到服务器。
2. 服务器发送的数据大于一定值时（<32KB都没问题，发送100+KB或400+KB的数据就失败了）。

其它情况都能发送成功，以下是代码：

 c


 // libuv 是 1.x 版本
void after_send(uv_write_t *write_req, int status)
{
    if (status != 0) {
        // 部署在不同机器上时，分别出现过 broken pipe 和 bad address in system call argument 这两种错误消息
        mydebug("send failed: %s", uv_strerror(status));
    } else {
        mydebug("send success");
    }

    free(write_req);
}

int send_bytes(client_t *client, tCString bytes, size_t len)
{
    uv_write_t *write_req = malloc(sizeof(*write_req));
    // bytes 所指向的内存是有效的，并且始终没有 free
    write_req->data = (void *)bytes;
    uv_buf_t send_buf = {
        .base = (char *)bytes,
        .len  = len
    };

    uv_write(write_req, (uv_stream_t *)&client->handle, &send_buf, 1, after_send);

    return 0;
}

我的问题是： 引起这个bug的可能原因是什么？

更新 ：传输1MB的文件时，客户端ACK得很慢（为什么），下面是抓包的结果（只选取了部分）：

 tcpdump: data link type PKTAP
listening on any, link-type PKTAP (Packet Tap), capture size 65535 bytes

Seconds    Port  > Port

15.576708  8883  > 52630 [.]  seq 1:16333        ack 306    win 9167  len 16332
15.576711  8883  > 52630 [.]  seq 16333:32665    ack 306    win 9167  len 16332
15.576714  8883  > 52630 [.]  seq 32665:48997    ack 306    win 9167  len 16332
15.576717  8883  > 52630 [.]  seq 48997:65329    ack 306    win 9167  len 16332
15.576731  8883  > 52630 [.]  seq 1:16333        ack 306    win 9167  len 16332
15.576736  8883  > 52630 [.]  seq 16333:32665    ack 306    win 9167  len 16332
15.576739  8883  > 52630 [.]  seq 65329:81661    ack 306    win 9167  len 16332
15.576742  8883  > 52630 [.]  seq 32665:48997    ack 306    win 9167  len 16332
15.576745  8883  > 52630 [.]  seq 81661:97993    ack 306    win 9167  len 16332
15.576748  8883  > 52630 [.]  seq 48997:65329    ack 306    win 9167  len 16332

15.576750  8883  > 52630 [.]  seq 97993:114325   ack 306    win 9167  len 16332
15.576754  8883  > 52630 [.]  seq 114325:130657  ack 306    win 9167  len 16332
15.576779  52630 > 8883  [.]  ack 32665          win 7145   len 0
15.576789  52630 > 8883  [.]  ack 65329          win 13269  len 0

15.576791  8883  > 52630 [.]  seq 65329:81661    ack 306    win 9167  len 16332
15.576795  8883  > 52630 [.]  seq 81661:97993    ack 306    win 9167  len 16332
15.576800  8883  > 52630 [.]  seq 97993:114325   ack 306    win 9167  len 16332
15.576803  8883  > 52630 [.]  seq 114325:130657  ack 306    win 9167  len 16332
15.576807  52630 > 8883  [.]  ack 32665          win 7145   len 0
15.576808  52630 > 8883  [.]  ack 65329          win 13269  len 0

15.576841  8883  > 52630 [.]  seq 130657:146989  ack 306    win 9167  len 16332
15.576847  8883  > 52630 [.]  seq 146989:163321  ack 306    win 9167  len 16332
15.576851  8883  > 52630 [.]  seq 163321:179653  ack 306    win 9167  len 16332
15.576855  8883  > 52630 [P.] seq 179653:187949  ack 306    win 9167  len 8296
15.576862  8883  > 52630 [.]  seq 187949:204281  ack 306    win 9167  len 16332
15.576866  8883  > 52630 [.]  seq 204281:220613  ack 306    win 9167  len 16332
15.576870  8883  > 52630 [.]  seq 220613:236945  ack 306    win 9167  len 16332
15.576874  8883  > 52630 [P.] seq 236945:253277  ack 306    win 9167  len 16332
15.576879  8883  > 52630 [.]  seq 130657:146989  ack 306    win 9167  len 16332
15.576883  8883  > 52630 [.]  seq 146989:163321  ack 306    win 9167  len 16332
15.576887  8883  > 52630 [.]  seq 163321:179653  ack 306    win 9167  len 16332
15.576891  8883  > 52630 [P.] seq 179653:187949  ack 306    win 9167  len 8296
15.576894  8883  > 52630 [.]  seq 187949:204281  ack 306    win 9167  len 16332
15.576898  8883  > 52630 [.]  seq 204281:220613  ack 306    win 9167  len 16332
15.576901  8883  > 52630 [.]  seq 220613:236945  ack 306    win 9167  len 16332
15.576905  8883  > 52630 [P.] seq 236945:253277  ack 306    win 9167  len 16332

15.947181  8883  > 52630 [.]  seq 65329:81661    ack 306    win 9167  len 16332
15.947222  8883  > 52630 [.]  seq 65329:81661    ack 306    win 9167  len 16332
16.350140  8883  > 52630 [.]  seq 65329:66517    ack 306    win 9167  len 1188
16.350151  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
16.350156  8883  > 52630 [.]  seq 67705:68893    ack 306    win 9167  len 1188
16.350161  8883  > 52630 [.]  seq 68893:70081    ack 306    win 9167  len 1188
16.350165  8883  > 52630 [.]  seq 65329:66517    ack 306    win 9167  len 1188
16.350167  8883  > 52630 [.]  seq 70081:71269    ack 306    win 9167  len 1188
16.350170  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
16.350173  8883  > 52630 [.]  seq 71269:72457    ack 306    win 9167  len 1188
16.350189  8883  > 52630 [.]  seq 72457:73645    ack 306    win 9167  len 1188
16.350194  8883  > 52630 [.]  seq 73645:74833    ack 306    win 9167  len 1188
16.350214  8883  > 52630 [.]  seq 67705:68893    ack 306    win 9167  len 1188
16.350218  8883  > 52630 [.]  seq 68893:70081    ack 306    win 9167  len 1188
16.350220  8883  > 52630 [.]  seq 70081:71269    ack 306    win 9167  len 1188
16.350221  8883  > 52630 [.]  seq 71269:72457    ack 306    win 9167  len 1188
16.350223  8883  > 52630 [.]  seq 72457:73645    ack 306    win 9167  len 1188
16.350225  8883  > 52630 [.]  seq 73645:74833    ack 306    win 9167  len 1188

16.451118  52630 > 8883  [.]  ack 66517          win 13195  len 0
16.451136  52630 > 8883  [.]  ack 66517          win 13195  len 0
16.451168  8883  > 52630 [.]  seq 74833:76021    ack 306    win 9167  len 1188
16.451174  8883  > 52630 [.]  seq 76021:77209    ack 306    win 9167  len 1188
16.451177  8883  > 52630 [.]  seq 74833:76021    ack 306    win 9167  len 1188
16.451179  8883  > 52630 [.]  seq 76021:77209    ack 306    win 9167  len 1188
16.955120  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
16.955155  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
17.760139  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
17.760165  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
19.174900  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
19.174925  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
21.792942  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188
21.792961  8883  > 52630 [.]  seq 66517:67705    ack 306    win 9167  len 1188

26.803909  8883  > 52630 [.]  seq 66517:82849    ack 306    win 9167  len 16332
26.803938  8883  > 52630 [.]  seq 66517:82849    ack 306    win 9167  len 16332
26.803943  8883  > 52630 [.]  seq 82849:99181    ack 306    win 9167  len 16332
26.803947  8883  > 52630 [.]  seq 99181:115513   ack 306    win 9167  len 16332
26.803952  8883  > 52630 [.]  seq 115513:131845  ack 306    win 9167  len 16332
26.803955  8883  > 52630 [.]  seq 131845:148177  ack 306    win 9167  len 16332
26.803958  8883  > 52630 [.]  seq 148177:164509  ack 306    win 9167  len 16332
26.803961  8883  > 52630 [.]  seq 164509:180841  ack 306    win 9167  len 16332
26.803964  8883  > 52630 [.]  seq 180841:197173  ack 306    win 9167  len 16332
26.803974  8883  > 52630 [.]  seq 82849:99181    ack 306    win 9167  len 16332
26.803978  8883  > 52630 [.]  seq 99181:115513   ack 306    win 9167  len 16332
26.803982  8883  > 52630 [.]  seq 115513:131845  ack 306    win 9167  len 16332
26.803985  8883  > 52630 [.]  seq 131845:148177  ack 306    win 9167  len 16332
26.803989  8883  > 52630 [.]  seq 148177:164509  ack 306    win 9167  len 16332
26.803992  8883  > 52630 [.]  seq 164509:180841  ack 306    win 9167  len 16332
26.803995  8883  > 52630 [.]  seq 180841:197173  ack 306    win 9167  len 16332

34.230610  8883  > 52630 [.]  seq 66517:82849    ack 306    win 9167  len 16332
34.230629  8883  > 52630 [.]  seq 66517:82849    ack 306    win 9167  len 16332
34.230636  8883  > 52630 [.]  seq 82849:99181    ack 306    win 9167  len 16332
34.230641  8883  > 52630 [.]  seq 99181:115513   ack 306    win 9167  len 16332
34.230646  8883  > 52630 [.]  seq 115513:131845  ack 306    win 9167  len 16332
34.230652  8883  > 52630 [.]  seq 131845:148177  ack 306    win 9167  len 16332
34.230657  8883  > 52630 [.]  seq 148177:164509  ack 306    win 9167  len 16332
34.230662  8883  > 52630 [.]  seq 164509:180841  ack 306    win 9167  len 16332
34.230667  8883  > 52630 [.]  seq 180841:197173  ack 306    win 9167  len 16332
34.230686  8883  > 52630 [.]  seq 82849:99181    ack 306    win 9167  len 16332
34.230690  8883  > 52630 [.]  seq 99181:115513   ack 306    win 9167  len 16332
34.230693  8883  > 52630 [.]  seq 115513:131845  ack 306    win 9167  len 16332
34.230697  8883  > 52630 [.]  seq 131845:148177  ack 306    win 9167  len 16332
34.230701  8883  > 52630 [.]  seq 148177:164509  ack 306    win 9167  len 16332
34.230704  8883  > 52630 [.]  seq 164509:180841  ack 306    win 9167  len 16332
34.230708  8883  > 52630 [.]  seq 180841:197173  ack 306    win 9167  len 16332

48.850193  8883  > 52630 [.]  seq 66517:82849    ack 306    win 9167  len 16332
48.850219  8883  > 52630 [.]  seq 66517:82849    ack 306    win 9167  len 16332
48.850242  8883  > 52630 [.]  seq 82849:99181    ack 306    win 9167  len 16332
48.850246  8883  > 52630 [.]  seq 99181:115513   ack 306    win 9167  len 16332
48.850249  8883  > 52630 [.]  seq 115513:131845  ack 306    win 9167  len 16332
48.850252  8883  > 52630 [.]  seq 131845:148177  ack 306    win 9167  len 16332
48.850254  8883  > 52630 [.]  seq 148177:164509  ack 306    win 9167  len 16332
48.850258  8883  > 52630 [.]  seq 164509:180841  ack 306    win 9167  len 16332
48.850261  8883  > 52630 [.]  seq 180841:197173  ack 306    win 9167  len 16332
48.850273  8883  > 52630 [.]  seq 82849:99181    ack 306    win 9167  len 16332
48.850276  8883  > 52630 [.]  seq 99181:115513   ack 306    win 9167  len 16332
48.850279  8883  > 52630 [.]  seq 115513:131845  ack 306    win 9167  len 16332
48.850282  8883  > 52630 [.]  seq 131845:148177  ack 306    win 9167  len 16332
48.850285  8883  > 52630 [.]  seq 148177:164509  ack 306    win 9167  len 16332
48.850287  8883  > 52630 [.]  seq 164509:180841  ack 306    win 9167  len 16332
48.850290  8883  > 52630 [.]  seq 180841:197173  ack 306    win 9167  len 16332

128 packets captured
362 packets received by filter
0 packets dropped by kernel