** Description changed:

+ [impact]
+ 
+ Using ifupdown, an interface's rp-filter value cannot be set to 2.
+ 
+ [test case]
+ 
+ On any system using ifupdown to manage interfaces, add to an interface's
+ config:
+ 
+ if-rp-filter 2
+ 
+ When the interface is brought up, its
+ /proc/sys/net/ipv4/conf/$IFACE/rp_filter value will be set to 1 instead
+ of 2.  With the fixed vlan package, its value will correctly be set to
+ 2.
+ 
+ [regression potential]
+ 
+ problems with this change could affect the value of an interface's
+ rp_filter value.
+ 
+ [other]
+ 
+ the upstream debian bug for this has been open for 3 years without
+ change, so it is unlikely debian will fix this.
+ 
+ [original description]
+ 
  When configuring a VLAN interface on /etc/network/interfaces, setting
  the ip-rp-filter value to 2 (loose mode reverse filtering) gets
  overridden by the /etc/network/if-up.d/ip script, which only allows for
  values 0 and 1.
  
  This is the relevant configuration in /etc/network/interfaces
  
  # The primary network interface
  auto eno1
  iface eno1 inet static
   address 10.1.2.36
   netmask 255.255.0.0
   gateway 10.1.1.2
   dns-search xxx.yy
   dns-nameservers 10.1.2.22 10.1.2.24
  
  # The administrative network
  auto eno1.2
  iface eno1.2 inet static
   address 172.16.1.8
   netmask 255.255.0.0
-  ip-rp-filter 2
+  ip-rp-filter 2
   vlan-raw-device eno1
- 
  
  But it does not get correctly set
  
  ~# cat /proc/sys/net/ipv4/conf/eno1.2/rp_filter
  1
  
  And this is the script overriding the configuration
  
  ~# cat /etc/network/if-up.d/ip
  #!/bin/sh
  # This should probably go into ifupdown
  # But usually only those with lots of interfaces (vlans) need these
  if [ -d "/proc/sys/net/ipv4/conf/$IFACE" ]
  then
   if [ -n "$IF_IP_PROXY_ARP" ]; then
    if [ "$IF_IP_PROXY_ARP" -eq "1" ]; then
     echo 1 > "/proc/sys/net/ipv4/conf/$IFACE/proxy_arp"
    else
     echo 0 > "/proc/sys/net/ipv4/conf/$IFACE/proxy_arp"
    fi
   fi
   if [ -n "$IF_IP_RP_FILTER" ]; then
    if [ "$IF_IP_RP_FILTER" -eq "0" ]; then
     echo 0 > "/proc/sys/net/ipv4/conf/$IFACE/rp_filter"
    else
     echo 1 > "/proc/sys/net/ipv4/conf/$IFACE/rp_filter"
    fi
   fi
  fi
  
  It checks if $IF_IP_RP_FILTER is 0 and sets it as 0, otherwise sets it
  as 1, so it never allows to set is to 2 (loose mode).

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https://bugs.launchpad.net/bugs/1716964

Title:
  VLAN network script if-up.d/ip limits rp_filter value to 0 or 1

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