RHEL 10 must not forward Internet Protocol version 4 (IPv4) source-routed packets.

Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It must be disabled unless it is absolutely required.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00073

Verify RHEL 10 will not accept IPv4 source-routed packets.

Check the value of the "net.ipv4.conf.all.accept_source_route" variable with the following command:

$ sudo sysctl net.ipv4.conf.all.accept_source_route net.ipv4.conf.all.accept_source_route = 0

If "net.ipv4.conf.all.accept_source_route" is not set to "0" or is missing, this is a finding.

Configure RHEL 10 to ignore IPv4 source-routed packets.

Create a configuration file if it does not already exist:

$ sudo vi /etc/sysctl.d/99-ipv4_accept_source.conf

Add the following line to the file:

net.ipv4.conf.all.accept_source_route = 0

Reload settings from all system configuration files with the following command:

$ sudo sysctl --system