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* [glibc/release/2.35/master] nscd: Fix netlink cache invalidation if epoll is used [BZ #29415]
@ 2022-09-06 16:32 Florian Weimer
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From: Florian Weimer @ 2022-09-06 16:32 UTC (permalink / raw)
  To: glibc-cvs

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f8ad66a4cab14ed294bf50e7a9eddb73da6cf307

commit f8ad66a4cab14ed294bf50e7a9eddb73da6cf307
Author: Fabian Vogt <fvogt@suse.de>
Date:   Wed Jul 27 11:44:07 2022 +0200

    nscd: Fix netlink cache invalidation if epoll is used [BZ #29415]
    
    Processes cache network interface information such as whether IPv4 or IPv6
    are enabled. This is only checked again if the "netlink timestamp" provided
    by nscd changed, which is triggered by netlink socket activity.
    
    However, in the epoll handler for the netlink socket, it was missed to
    assign the new timestamp to the nscd database. The handler for plain poll
    did that properly, copy that over.
    
    This bug caused that e.g. processes which started before network
    configuration got unusuable addresses from getaddrinfo, like IPv6 only even
    though only IPv4 is available:
    https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/1041
    
    It's a bit hard to reproduce, so I verified this by checking the timestamp
    on calls to __check_pf manually. Without this patch it's stuck at 1, now
    it's increasing on network changes as expected.
    
    Signed-off-by: Fabian Vogt <fvogt@suse.de>
    (cherry picked from commit 02ca25fef2785974011e9c5beecc99b900b69fd7)

Diff:
---
 NEWS               | 1 +
 nscd/connections.c | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/NEWS b/NEWS
index 1a16fc30a9..cabd3f0b5e 100644
--- a/NEWS
+++ b/NEWS
@@ -46,6 +46,7 @@ The following bugs are resolved with this release:
   [29214] nptl: pthread_setcanceltype fails to set type
   [29225] network: Mistyped define statement in socket/sys/socket.h in
     line 184
+  [29415] nscd: Fix netlink cache invalidation if epoll is used
   [29446] _dlopen now ignores dl_caller argument in static mode
   [29490] alpha: New __brk_call implementation is broken
   [29528] elf: Call __libc_early_init for reused namespaces
diff --git a/nscd/connections.c b/nscd/connections.c
index 61d1674eb4..531d2e83df 100644
--- a/nscd/connections.c
+++ b/nscd/connections.c
@@ -2284,7 +2284,8 @@ main_loop_epoll (int efd)
 					     sizeof (buf))) != -1)
 	      ;
 
-	    __bump_nl_timestamp ();
+	    dbs[hstdb].head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP]
+	      = __bump_nl_timestamp ();
 	  }
 # endif
 	else

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