platform: add bpf filter to ignore routes from routing daemons
Routing daemons can add a large amount of routes to the system. Currently NM receives netlink notifications for all those routes and exposes them on D-Bus. With many routes, the daemon becomes increasingly slow and uses a lot of memory.
The rtm_protocol field of the route indicates the source of the route. From /usr/include/linux/rtnetlink.h, the allowed values are:
#define RTPROT_UNSPEC 0
#define RTPROT_REDIRECT 1 /* Route installed by ICMP redirects;
not used by current IPv4 */
#define RTPROT_KERNEL 2 /* Route installed by kernel */
#define RTPROT_BOOT 3 /* Route installed during boot */
#define RTPROT_STATIC 4 /* Route installed by administrator */
/* Values of protocol >= RTPROT_STATIC are not interpreted by kernel;
they are just passed from user and back as is.
It will be used by hypothetical multiple routing daemons.
Note that protocol values should be standardized in order to
avoid conflicts.
*/
#define RTPROT_GATED 8 /* Apparently, GateD */
#define RTPROT_RA 9 /* RDISC/ND router advertisements */
#define RTPROT_MRT 10 /* Merit MRT */
#define RTPROT_ZEBRA 11 /* Zebra */
#define RTPROT_BIRD 12 /* BIRD */
#define RTPROT_DNROUTED 13 /* DECnet routing daemon */
#define RTPROT_XORP 14 /* XORP */
#define RTPROT_NTK 15 /* Netsukuku */
#define RTPROT_DHCP 16 /* DHCP client */
#define RTPROT_MROUTED 17 /* Multicast daemon */
#define RTPROT_KEEPALIVED 18 /* Keepalived daemon */
#define RTPROT_BABEL 42 /* Babel daemon */
#define RTPROT_OPENR 99 /* Open Routing (Open/R) Routes */
#define RTPROT_BGP 186 /* BGP Routes */
#define RTPROT_ISIS 187 /* ISIS Routes */
#define RTPROT_OSPF 188 /* OSPF Routes */
#define RTPROT_RIP 189 /* RIP Routes */
#define RTPROT_EIGRP 192 /* EIGRP Routes */Since NM uses only values <= RTPROT_STATIC, plus RTPROT_RA and RTPROT_DHCP, add a BPF filter to the netlink socket to discard notifications for other route types.