yintao707 opened a new pull request, #18324:
URL: https://github.com/apache/nuttx/pull/18324
## Summary
Previously, the server would add a new connection to the pending_list
and return POLLIN immediately after the server sent sock_sync (ns_ack).
This caused a race condition where poll() returned POLLIN, but accept()
would block waiting on sendsem until the client sent sock_sync.
This change defers the connection notification until the client's
sock_sync message is received. Now:
- Connection is added to pending_list in ept_cb when sock_sync arrives
- POLLIN is returned only after the full handshake completes
- accept() no longer blocks after poll() indicates readiness
old
```
Client Server User App
| | |
|-------- ns_create ----------->| |
| | |
|<------- ns_bind --------------| |
| (ns_ack) | |
| | |
| |--[add to pending_list]--->|
| |--[post recvsem]---------->|
| |--[notify POLLIN]--------->|
| | |
| | poll()
returns
| | |
| | accept()
called
| | |
| |<----[wait sendsem]--------| ←
阻塞!
| | |
|-------- sock_sync ----------->| |
| |--[post sendsem]---------->|
| | |
|<------- sock_sync ------------| accept()
returns
| | |
```
new
```
Client Server User App
| | |
|-------- ns_create ----------->| |
| | |
|<------- ns_bind --------------| |
| (ns_ack) | |
| |--[pending++] |
| | (NOT add to list yet) |
| | |
|-------- sock_sync ----------->| |
| | |
| |--[add to pending_list]--->|
| |--[post recvsem]---------->|
| |--[notify POLLIN]--------->|
| | |
|<------- sock_sync ------------| poll()
returns
| | |
| | accept()
called
| | |
| | (sendsize > 0 ✓) |
| | accept()
returns
| | |
```
## Impact
No impact on usage
## Testing
sim:rpproxy/ sim:rpserver
```
NuttShell (NSH) NuttX-12.12.0
server>
server> rpsock_server stream block hello proxy &
rpsock_server [9:100]
server> server: create socket SOCK_STREAM nonblock 0
server: bind cpu proxy, name hello ...
server: listen ...
server: try accept ...
server> cu
NuttShell (NSH) NuttX-12.12.0
proxy>
proxy>
proxy> rpsock_client stream block hello server &
rpsock_client [6:100]
proxy> client: create socket SOCK_STREAM nonblock 0
client: Connecting to server,hello...
server: Connection accepted -- 4
server: try accept ...
client: Connected
client send data, cnt 0, total len 64, BUFHEAD process0006, msg0000,
name:hello
client recv data process0006, msg0000, name:hello
client recv total 64, send total 64
client send data, cnt 1, total len 87, BUFHEAD process0006, msg0001,
name:hello
client recv data process0006, msg0001, name:hello
......
client recv data, act len 4, total 4095996
client recv done, total 4096000, endflags, send total 4096000
server recv data normal exit
server Complete ret 0, errno 0
client: Terminating
```
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