Documentation: networking: ip-sysctl: Document src_valid_mark sysctl

Provide documentation for src_valid_mark sysctl, which was added
in commit 28f6aeea3f12 ("net: restore ip source validation").

Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 83ff5158005af523f7b7464313a1c7f1f3b3ae05..581bfce86dca1a9c18a099e9edd037e483c320af 100644 (file)
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1446,6 +1446,25 @@ rp_filter - INTEGER
        Default value is 0. Note that some distributions enable it
        in startup scripts.
 
+src_valid_mark - BOOLEAN
+       - 0 - The fwmark of the packet is not included in reverse path
+         route lookup.  This allows for asymmetric routing configurations
+         utilizing the fwmark in only one direction, e.g., transparent
+         proxying.
+
+       - 1 - The fwmark of the packet is included in reverse path route
+         lookup.  This permits rp_filter to function when the fwmark is
+         used for routing traffic in both directions.
+
+       This setting also affects the utilization of fmwark when
+       performing source address selection for ICMP replies, or
+       determining addresses stored for the IPOPT_TS_TSANDADDR and
+       IPOPT_RR IP options.
+
+       The max value from conf/{all,interface}/src_valid_mark is used.
+
+       Default value is 0.
+
 arp_filter - BOOLEAN
        - 1 - Allows you to have multiple network interfaces on the same
          subnet, and have the ARPs for each interface be answered