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SubjectRe: /proc/sys/net/ip*/conf/all/* does not actually affect interfaces
Hello!

On Mon, Mar 02, 2009 at 01:27:18PM +0100, martin f krafft wrote:
> I was unpleasantly surprised last night that a rogue machine managed
> to alter the IPv6 default route of one of my servers, despite my
> sysctl configuration, which disables RA for "all" interfaces during
> the boot sequence. It also changes the "default" values:
...
> Yet, net.ipv6.conf.eth0.* values were unchanged, and routing
> advertisements honoured.
>
> This also applies to files in ipv4/, e.g. accept_redirects
...

As far as I researched for IPv4 some time ago, the "default" value gets
copied to newly created interfaces only once.
"all" on the other hand allways gets applied in addition to the current
setting, but it depends on the exact setting, if its ORed, ANDed, or
whatevered:
log_martians OR
accept_redirects AND
forwarding ?
mc_forwarding AND
medium_id
proxy_arp OR
shared_media OR
secure_redirects OR
send_redirects OR
bootp_relay AND
accept_source_route AND
rp_filter AND
arp_filter OR
arp_announce MAX
arp_ignore MAX
arp_accept
app_solicit
disable_policy
disable_xfrm
tag
(see include/linux/inetdevice.h:83 for IN_DEV_{AND,OR,MAX}CONF)
Putting a new value in "all" doesn't change the value you read from
"$interface", but it only gets computed and used internally.

BYtE
Philipp
--
/ / (_)__ __ ____ __ Philipp Hahn
/ /__/ / _ \/ // /\ \/ /
/____/_/_//_/\_,_/ /_/\_\ pmhahn@titan.lahn.de

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