This flag identifies that the address was obtained through DHCP. Today there is no easy way to find out whether an address on an interface is DHCP controlled or is static. Either you will need to grep for 'dhclient' process (or something else in case one is using a different DHCP client) or if you are using NetworkManager (or some such), then you will need to query through their interface to find out if an address is DHCP or not.
This flag will be set by the DHCP clients in the userspace when it brings up the DHCP address on an interface. For example: ISC DHCP client (aka dhclient) today brings up the address on an interface by running ip-address(8) command (in dhclient-script). This command can be extended to include 'dhcp' keyword in its 'add' or 'replace' subcommand. Once this flag is set, the show subcommand can display the keyword 'dhcp' against the address to indicate that the address was obtained through DHCP. This flag can also be set and obtained programmatically using AF_NETLINK. Besides providing observability, this flag will be useful for applications that need to prevent/allow certain settings on addresses based on whether they are DHCP or not. Signed-off-by: Girish Moodalbail <[email protected]> --- include/uapi/linux/if_addr.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/uapi/linux/if_addr.h b/include/uapi/linux/if_addr.h index 4318ab1..61aa8f8 100644 --- a/include/uapi/linux/if_addr.h +++ b/include/uapi/linux/if_addr.h @@ -52,6 +52,7 @@ enum { #define IFA_F_NOPREFIXROUTE 0x200 #define IFA_F_MCAUTOJOIN 0x400 #define IFA_F_STABLE_PRIVACY 0x800 +#define IFA_F_DHCP 0x1000 struct ifa_cacheinfo { __u32 ifa_prefered; -- 1.8.3.1
