msg_constr_attr.c

00001 struct nl_msg *build_msg(int ifindex, struct nl_addr *lladdr, int mtu)
00002 {
00003         struct nl_msg *msg;
00004         struct nlattr *info, *vlan;
00005         struct ifinfomsg ifi = {
00006                 .ifi_family = AF_INET,
00007                 .ifi_index = ifindex,
00008         };
00009 
00010         /* Allocate a default sized netlink message */
00011         if (!(msg = nlmsg_alloc_simple(RTM_SETLINK, 0)))
00012                 return NULL;
00013 
00014         /* Append the protocol specific header (struct ifinfomsg)*/
00015         if (nlmsg_append(msg, &ifi, sizeof(ifi), NLMSG_ALIGNTO) < 0)
00016                 goto nla_put_failure
00017 
00018         /* Append a 32 bit integer attribute to carry the MTU */
00019         NLA_PUT_U32(msg, IFLA_MTU, mtu);
00020 
00021         /* Append a unspecific attribute to carry the link layer address */
00022         NLA_PUT_ADDR(msg, IFLA_ADDRESS, lladdr);
00023 
00024         /* Append a container for nested attributes to carry link information */
00025         if (!(info = nla_nest_start(msg, IFLA_LINKINFO)))
00026                 goto nla_put_failure;
00027 
00028         /* Put a string attribute into the container */
00029         NLA_PUT_STRING(msg, IFLA_INFO_KIND, "vlan");
00030 
00031         /*
00032          * Append another container inside the open container to carry
00033          * vlan specific attributes
00034          */
00035         if (!(vlan = nla_nest_start(msg, IFLA_INFO_DATA)))
00036                 goto nla_put_failure;
00037 
00038         /* add vlan specific info attributes here... */
00039 
00040         /* Finish nesting the vlan attributes and close the second container. */
00041         nla_nest_end(msg, vlan);
00042 
00043         /* Finish nesting the link info attribute and close the first container. */
00044         nla_nest_end(msg, info);
00045 
00046         return msg;
00047 
00048 nla_put_failure:
00049         nlmsg_free(msg);
00050         return NULL;
00051 }