The strict mode, as specified in RFC 3704, section 2.2, causes packets to be dropped by the kernel if they arrive with a source IP address that is not expected on the interface they arrived in. This prevents internal spoofing attacks, and is considered best practice among the industry.
After a discussion with Michael, we reached the conclusion that permitting users to configure the operating mode of RPF in IPFire causes more harm than good. The scenarios where strict RPF is not usable are negligible, and the vast majority of IPFire's userbase won't even notice a difference.
This supersedes 495b4ca2-5a4b-2ffa-8306-38f152889582@ipfire.org.
Suggested-by: Michael Tremer michael.tremer@ipfire.org Signed-off-by: Peter Müller peter.mueller@ipfire.org --- config/etc/sysctl.conf | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/config/etc/sysctl.conf b/config/etc/sysctl.conf index 5fc3e3d89..7fe397bb7 100644 --- a/config/etc/sysctl.conf +++ b/config/etc/sysctl.conf @@ -12,13 +12,13 @@ net.ipv4.tcp_syn_retries = 3 net.ipv4.tcp_synack_retries = 3
net.ipv4.conf.default.arp_filter = 1 -net.ipv4.conf.default.rp_filter = 2 +net.ipv4.conf.default.rp_filter = 1 net.ipv4.conf.default.accept_redirects = 0 net.ipv4.conf.default.accept_source_route = 0 net.ipv4.conf.default.log_martians = 1
net.ipv4.conf.all.arp_filter = 1 -net.ipv4.conf.all.rp_filter = 2 +net.ipv4.conf.all.rp_filter = 1 net.ipv4.conf.all.accept_redirects = 0 net.ipv4.conf.all.accept_source_route = 0 net.ipv4.conf.all.log_martians = 1