route: replace hardcoded constants with defines

[Klemens Nanni]

These seem more descriptive to me.

No binary change.

Feedback? OK?

Index: route.c
===================================================================
RCS file: /cvs/src/sbin/route/route.c,v
retrieving revision 1.214
diff -u -p -r1.214 route.c
--- route.c     1 May 2018 18:14:10 -0000       1.214
+++ route.c     13 Jun 2018 18:08:12 -0000
@@ -754,13 +754,13 @@ inet_makenetandmask(u_int32_t net, struc
        else if (bits) {
                addr = net;
                mask = 0xffffffff << (32 - bits);
-       } else if (net < 128) {
+       } else if (net < IN_CLASSA_MAX) {
                addr = net << IN_CLASSA_NSHIFT;
                mask = IN_CLASSA_NET;
-       } else if (net < 65536) {
+       } else if (net < IN_CLASSB_MAX) {
                addr = net << IN_CLASSB_NSHIFT;
                mask = IN_CLASSB_NET;
-       } else if (net < 16777216L) {
+       } else if (net < (1 << 24)) {
                addr = net << IN_CLASSC_NSHIFT;
                mask = IN_CLASSC_NET;
        } else {
@@ -1003,7 +1003,7 @@ getmplslabel(char *s, int in)
        const char *errstr;
        u_int32_t label;
 
-       label = strtonum(s, 0, 0x000fffff, &errstr);
+       label = strtonum(s, 0, MPLS_LABEL_MAX, &errstr);
        if (errstr)
                errx(1, "bad label: %s is %s", s, errstr);
        if (in) {
@@ -1117,7 +1117,7 @@ rtmsg(int cmd, int flags, int fmask, uin
                cmd = RTM_CHANGE;
        else if (cmd == 'g') {
                cmd = RTM_GET;
-               if (so_ifp.sa.sa_family == 0) {
+               if (so_ifp.sa.sa_family == AF_UNSPEC) {
                        so_ifp.sa.sa_family = AF_LINK;
                        so_ifp.sa.sa_len = sizeof(struct sockaddr_dl);
                        rtm_addrs |= RTA_IFP;
@@ -1185,7 +1185,7 @@ mask_addr(union sockunion *addr, union s
        switch (addr->sa.sa_family) {
        case AF_INET:
        case AF_INET6:
-       case 0:
+       case AF_UNSPEC:
                return;
        }
        cp1 = mask->sa.sa_len + 1 + (char *)addr;