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[lwip-devel] [bug #58817] SNTP - MEMP_SYS_TIMEOUT memory pool exhaustion
From: |
yuanjianmin |
Subject: |
[lwip-devel] [bug #58817] SNTP - MEMP_SYS_TIMEOUT memory pool exhaustion when receive KOD packet |
Date: |
Thu, 20 May 2021 06:02:19 -0400 (EDT) |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:88.0) Gecko/20100101 Firefox/88.0 |
Follow-up Comment #1, bug #58817 (project lwip):
[comment #0 original submission:]
> There appears to be an issue when receiving SNTP Kiss Of Death packets.
After receiving several KOD packets, I started to see 'sys_timeout: timeout !=
NULL, pool MEMP_SYS_TIMEOUT is empty' assertions displayed.
>
> Looking at SNTP.C, around line 536, we have two sys_untimeout functions
calls to cancel active timeouts when receiving a good packet. However, there
isn't a corresponding sys_untimeout(sntp_request) just before the
sntp_try_next_server call around line 553 when receiving a KOD packet. Since
the timeout isn't cancelled, this appears to reduce the memory pool which
eventually results in the assertion displayed above. Changing the code to :
>
> if (sntp_opmode == SNTP_OPMODE_POLL) {
> /* Kiss-of-death packet. Use another server or increase UPDATE_DELAY.
*/
> sys_untimeout(sntp_request, NULL);
>
> sntp_try_next_server(NULL);
> }
>
> appears to solve the problem.
>
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