gateway field missing in netlink message

* gateway field missing in netlink message
@ 2022-05-19  6:11 Magesh  M P
  0 siblings, 0 replies; 14+ messages in thread
From: Magesh  M P @ 2022-05-19  6:11 UTC (permalink / raw)
  To: David Ahern, stephen, netdev

Hi Dave/Steve,

Thanks for your support....

The Linux kernel is sending the route information with dual gateways properly to the netlink listener in the vpp stack.

The following parser logic is used in netlink listener to retrieve the two gateways in RTA_MULTIPATH attribute

      if (route_attribute->rta_type == RTA_MULTIPATH)
        {
           printf("AMG - RTA_MULTIPATH\n");
           /* Get RTA_MULTIPATH data */
           struct rtnexthop *nhptr = (struct rtnexthop*) RTA_DATA(route_attribute);
           int rtnhp_len = RTA_PAYLOAD(route_attribute);
           /* Is the message complete? */
           if (rtnhp_len < (int) sizeof(*nhptr) || 
              nhptr->rtnh_len > rtnhp_len)
           {
              continue;
           }
           /* Get the size of the attributes */
           unsigned int attrlen = rtnhp_len - sizeof(struct rtnexthop);
           if (attrlen) 
           {
             /* Retrieve attributes */
             struct rtattr *attr = RTNH_DATA(nhptr);
			 int len = RTA_PAYLOAD(route_attribute);
			 struct rtnexthop *nh = RTA_DATA(route_attribute);

			 for(;;)
		     {
				 if (len < sizeof(*nh)) 
				 {
				 	printf("BREAK -attr->rta_len[%u]\n", len);
					 break;
				 }
				 if (nh->rtnh_len > len) 
				 {
				 	printf("BREAK2 -attr->rta_len[%u]\n", len);
				    break;
				 }

                 printf("RTA_MULTIPATH - attr=[%p] attr->rta_len=[%u]attr->rta_type=[%u] DATA=[%p]\n", attr, attr->rta_len, attr->rta_type, RTA_DATA(attr));

				 if (nh->rtnh_len > sizeof(*nh)) 
				 {
					unsigned short type;				 
					unsigned int len_nh=nh->rtnh_len - sizeof(*nh);
					struct rtattr* attr2=RTNH_DATA(nh);
				    while (RTA_OK(attr2, len_nh)) 
					{
					    type = attr2->rta_type & ~0;
                        if ((type <= RTA_MAX))
                        {
                             attr = attr2;
                        }
						attr2 = RTA_NEXT(attr2, len_nh);
					}
				 } 

                 if (attr->rta_type == RTA_GATEWAY) 
                 {
                     /* Next hops from RTA_MULTIPATH are 
                      * contained in RTA_GATEWAY attributes! 
                      */
                     inet_ntop(AF_INET, RTA_DATA(attr), gateway_address, sizeof(gateway_address)); 
                     printf("GATEWAY: route to destination --> %s/%d proto %d and gateway %s\n", destination_address, route_netmask, route_protocol, gateway_address);
                 }
				len -= NLMSG_ALIGN(nh->rtnh_len);
				nh = RTNH_NEXT(nh);			
              }
           }
         }

^ permalink raw reply	[flat|nested] 14+ messages in thread