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Code Issues Releases Wiki Activity

remove unnecessary assertion in dns_dispatch_connect()

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When a thread calls dns_dispatch_connect() on an unconnected TCP socket
it sets `tcpstate` from `DNS_DISPATCHSTATE_NONE` to `_CONNECTING`.
Previously, it then INSISTed that there were no pending connections
before calling isc_nm_tcpdnsconnect().

If a second thread called dns_dispatch_connect() during that window
of time, it could add a pending connection to the list, and trigger
an assertion failure.

This commit removes the INSIST since the condition is actually
harmless.
This commit is contained in:
Evan Hunt 2022-07-13 12:38:55 -07:00
parent 84c353b5cf
commit e1c81f9b1b
2 changed files with 4 additions and 1 deletions
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4
CHANGES
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@ -1,3 +1,7 @@
5927. [bug] A race was possible in dns_dispatch_connect()
that could trigger an assertion failure if two
threads called it near-simultaneously. [GL #3456]
5926. [func] Handle transient TCP connect() EADDRINUSE failures
on FreeBSD (and possibly other BSDs) by trying three
times before giving up. [GL #3451]

1
lib/dns/dispatch.c
View File

@ -1812,7 +1812,6 @@ dns_dispatch_connect(dns_dispentry_t *resp) {
case DNS_DISPATCHSTATE_NONE:
/* First connection, continue with connecting */
LOCK(&disp->lock);
INSIST(ISC_LIST_EMPTY(disp->pending));
ISC_LIST_APPEND(disp->pending, resp, plink);
UNLOCK(&disp->lock);
dns_dispatch_attach(disp, &(dns_dispatch_t *){ NULL });