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DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Queue-Id: 57CF56B51F X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Score: -3.51 On 5/4/26 6:35 PM, Ido Schimmel wrote: > On Mon, May 04, 2026 at 12:11:40AM +0200, Fernando Fernandez Mancera wrote: >> When a router temporarily deprecates an IPv6 prefix (either by sending a >> Router Advertisement with Preferred Lifetime = 0 or by letting the >> lifetime expire) and later restores it, the kernel permanently loses its >> ability to generate temporary privacy addresses (RFC 8981) for that >> prefix. >> >> This happens because the address worker attempts to generate a >> replacement temporary address when the current one nears expiration. As >> the base prefix is deprecated already, the generation fails, burning the >> retry counter for temporary address generation of that prefix. >> >> When the router eventually restores the prefix, the temporary address >> becomes active again. However, once it naturally expires, the kernel >> sees the exhausted retry limit and permanently stops generating new >> privacy addresses. > > It's not clear to me to which "retry counter" you are referring to. Are > you referring to the counter of the temporary address or to that of the > "public address" from which it was generated? > > AFAICT, in the case of temporary addresses (those w/o "mngtmpaddr") this > isn't really a counter, but a boolean that tells you if an address was > already spawned from this address. > >> >> Fix this by verifying that the base prefix has sufficient preferred >> lifetime remaining before attempting to generate a new temporary >> address. This prevents the worker from burning through its retry counter >> during temporary network deprecation events like a router reboot. > > Again, I think that "retry counter" here is confusing. IIUC, what > happens is that the kernel marks the temporary address as having spawned > an address ('ifp->regen_count++'), then tries to spawn an address by > calling ipv6_create_tempaddr(), which fails because the preferred > lifetime of the public address is 0. > Yes, you are right. I used the word counter as the variable was ifp->regen_count although for temporary addresses it is just a boolean. Let me modify the commit message to make it clear. Thanks Ido for reviewing! >> >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >> Reported-by: Łukasz Stelmach >> Closes: https://lore.kernel.org/netdev/87340td30q.fsf%25steelman@post.pl/ >> Signed-off-by: Fernando Fernandez Mancera >> --- >> net/ipv6/addrconf.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c >> index 5476b6536eb7..f6a3d9da3cb1 100644 >> --- a/net/ipv6/addrconf.c >> +++ b/net/ipv6/addrconf.c >> @@ -4654,9 +4654,11 @@ static void addrconf_verify_rtnl(struct net *net) >> !ifp->regen_count && ifp->ifpub) { >> /* This is a non-regenerated temporary addr. */ >> >> + unsigned long pub_age = (now - READ_ONCE(ifp->ifpub->tstamp)) / HZ; >> unsigned long regen_advance = ipv6_get_regen_advance(ifp->idev); >> >> - if (age + regen_advance >= ifp->prefered_lft) { >> + if (age + regen_advance >= ifp->prefered_lft && >> + pub_age + regen_advance < READ_ONCE(ifp->ifpub->prefered_lft)) { >> struct inet6_ifaddr *ifpub = ifp->ifpub; >> if (time_before(ifp->tstamp + ifp->prefered_lft * HZ, next)) >> next = ifp->tstamp + ifp->prefered_lft * HZ; >> -- >> 2.53.0 >>