masaori335 commented on issue #7915:
URL: https://github.com/apache/trafficserver/issues/7915#issuecomment-855543295
After #7809, `read_from_net` raises `VC_EVENT_ERROR` when the origin server
resets the connection after sending the response.
<details><summary>`VC_EVENT_ERROR` on
`HttpSM::state_read_server_response_header`</summary>
```
(gdb) bt
#0 HttpSM::state_read_server_response_header (this=0x7ffff02a03b0, event=3,
data=0x7fffec1552e8) at HttpSM.cc:1981
#1 0x0000000000594768 in HttpSM::main_handler (this=0x7ffff02a03b0,
event=3, data=0x7fffec1552e8) at HttpSM.cc:2703
#2 0x00000000007e052e in read_signal_and_update (event=3,
vc=0x7fffec155100) at UnixNetVConnection.cc:83
#3 0x00000000007e4f41 in UnixNetVConnection::readSignalAndUpdate (event=3,
this=0x7fffec155100) at UnixNetVConnection.cc:1043
#4 read_from_net (nh=0x7ffff3845180, vc=0x7fffec155100,
thread=0x7ffff3841010) at UnixNetVConnection.cc:204
#5 0x00000000007d1947 in NetHandler::process_ready_list
(this=this@entry=0x7ffff3845180) at UnixNet.cc:415
#6 0x00000000007d1d13 in NetHandler::waitForActivity (this=0x7ffff3845180,
timeout=<optimized out>) at UnixNet.cc:546
#7 0x00000000008271aa in EThread::execute_regular
(this=this@entry=0x7ffff3841010) at I_PriorityEventQueue.h:115
#8 0x0000000000827412 in EThread::execute (this=0x7ffff3841010) at
UnixEThread.cc:364
#9 EThread::execute (this=0x7ffff3841010) at UnixEThread.cc:342
#10 0x00000000008257ea in spawn_thread_internal (a=0xd5e7f0) at Thread.cc:92
#11 0x00007ffff68a614a in start_thread () from /lib64/libpthread.so.0
#12 0x00007ffff5aa4f23 in clone () from /lib64/libc.so.6
(gdb) frame 4
#4 read_from_net (nh=0x7ffff3845180, vc=0x7fffec155100,
thread=0x7ffff3841010) at UnixNetVConnection.cc:204
204 vc->readSignalAndUpdate(VC_EVENT_ERROR);
(gdb) p vc->error
$1 = 104
```
</details>
<details><summary>tcpdump trafficserver <-> origin server</summary>
```
1 2021-06-07 02:51:09.889582 0.000000 TCP 127.0.0.1 51260 127.0.0.1
61000 74 51260 → 61000 [SYN] Seq=0 Win=43690 Len=0 MSS=65495 SACK_PERM=1
TSval=1062468354 TSecr=0 WS=128
2 2021-06-07 02:51:09.889596 0.000014 TCP 127.0.0.1 61000 127.0.0.1
51260 74 61000 → 51260 [SYN, ACK] Seq=0 Ack=1 Win=43690 Len=0 MSS=65495
SACK_PERM=1 TSval=1062468354 TSecr=1062468354 WS=128
3 2021-06-07 02:51:09.889605 0.000023 TCP 127.0.0.1 51260 127.0.0.1
61000 66 51260 → 61000 [ACK] Seq=1 Ack=1 Win=43776 Len=0 TSval=1062468354
TSecr=1062468354
4 2021-06-07 02:51:09.889839 0.000257 TCP 127.0.0.1 51260 127.0.0.1
61000 282 POST / HTTP/1.1 [TCP segment of a reassembled PDU]
5 2021-06-07 02:51:09.889845 0.000263 TCP 127.0.0.1 61000 127.0.0.1
51260 66 61000 → 51260 [ACK] Seq=1 Ack=217 Win=44800 Len=0 TSval=1062468355
TSecr=1062468355
6 2021-06-07 02:51:09.889993 0.000411 HTTP 127.0.0.1 51260
127.0.0.1 61000 16487 POST / HTTP/1.1
7 2021-06-07 02:51:09.889999 0.000417 TCP 127.0.0.1 61000 127.0.0.1
51260 66 61000 → 51260 [ACK] Seq=1 Ack=16638 Win=175744 Len=0
TSval=1062468355 TSecr=1062468355
8 2021-06-07 02:51:09.891157 0.001575 TCP 127.0.0.1 61000 127.0.0.1
51260 335 HTTP/1.1 405 METHOD NOT ALLOWED [TCP segment of a reassembled PDU]
9 2021-06-07 02:51:09.891169 0.001587 TCP 127.0.0.1 51260 127.0.0.1
61000 66 51260 → 61000 [ACK] Seq=16638 Ack=270 Win=44800 Len=0
TSval=1062468356 TSecr=1062468356
10 2021-06-07 02:51:09.891184 0.001602 HTTP 127.0.0.1 61000
127.0.0.1 51260 244 HTTP/1.1 405 METHOD NOT ALLOWED (text/html)
11 2021-06-07 02:51:09.891189 0.001607 TCP 127.0.0.1 51260 127.0.0.1
61000 66 51260 → 61000 [ACK] Seq=16638 Ack=448 Win=45952 Len=0
TSval=1062468356 TSecr=1062468356
12 2021-06-07 02:51:09.891231 0.001649 TCP 127.0.0.1 61000 127.0.0.1
51260 66 61000 → 51260 [RST, ACK] Seq=448 Ack=16638 Win=175744 Len=0
TSval=1062468356 TSecr=1062468356
```
</details>
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