Fix the interface alias code. Previously, I was expecting something

like

tun0: flags=blah
	10.0.0.1 -> 10.0.0.100
	10.0.0.2 -> 10.0.0.100
	10.0.0.3 -> 10.0.0.100

to DTRT, despite the SIOCAIFADDR for each new alias returning
-1 & EEXIST while adding the alias anyway.  In real life, once
we have the second alias with the same destination, nothing will
route any more !  Also, because I was ignoring EEXIST, the
dynamic IP assignment code was assigning duplicate addresses
('cos it was being lied to by iface_inAdd()).

Now we have

tun0: flags=blah
	10.0.0.1 -> 255.255.255.255
	10.0.0.2 -> 10.0.0.100
	10.0.0.3 -> 255.255.255.255

This works - stuff bound to 10.1 & 10.3 will be considered alive
by the kernel, and when they route back to the tun device, the
packets get aliased to 10.2 and go out to 10.100 (as with the
original plan).

We still see the EEXIST in SIOCAIFADDR, but ignore it when our
destination is 255.255.255.255, assuming that the alias *was*
actually added.

Additionally, ``iface add'' may now optionally be given only
the interface address.  The mask & destination default to
255.255.255.255.

1 files changed, 62 insertions, 12 deletions

diff --git a/usr.sbin/ppp/iface.c b/usr.sbin/ppp/iface.c
index c217690..bca10ee 100644
--- a/usr.sbin/ppp/iface.c
+++ b/usr.sbin/ppp/iface.c
@@ -23,7 +23,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id:$
+ *	$Id: iface.c,v 1.1 1998/10/22 02:32:49 brian Exp $
  */
 
 #include <sys/types.h>
@@ -232,6 +232,7 @@ iface_addr_Zap(const char *name, struct iface_addr *addr)
     me->sin_len = peer->sin_len = sizeof(struct sockaddr_in);
     me->sin_addr = addr->ifa;
     peer->sin_addr = addr->brd;
+    log_Printf(LogDEBUG, "Delete %s\n", inet_ntoa(addr->ifa));
     if (ID0ioctl(s, SIOCDIFADDR, &ifra) < 0)
       log_Printf(LogWARN, "iface_addr_Zap: ioctl(SIOCDIFADDR, %s): %s\n",
                  inet_ntoa(addr->ifa), strerror(errno));
@@ -256,7 +257,7 @@ int
 iface_inAdd(struct iface *iface, struct in_addr ifa, struct in_addr mask,
             struct in_addr brd, int how)
 {
-  int slot, s;
+  int slot, s, chg;
   struct ifaliasreq ifra;
   struct sockaddr_in *me, *peer, *msk;
   struct iface_addr *addr;
@@ -284,27 +285,76 @@ iface_inAdd(struct iface *iface, struct in_addr ifa, struct in_addr mask,
     return 0;
   }
 
+  /*
+   * We've gotta be careful here.  If we try to add an address with the
+   * same destination as an existing interface, nothing will work.
+   * Instead, we tweak all previous address entries that match the
+   * to-be-added destination to 255.255.255.255 (w/ a similar netmask).
+   * There *may* be more than one - if the user has ``iface add''ed
+   * stuff previously.
+   */
+  for (chg = 0; chg < iface->in_addrs; chg++) {
+    if ((iface->in_addr[chg].brd.s_addr == brd.s_addr &&
+         brd.s_addr != INADDR_BROADCAST) || chg == slot) {
+      memset(&ifra, '\0', sizeof ifra);
+      strncpy(ifra.ifra_name, iface->name, sizeof ifra.ifra_name - 1);
+      me = (struct sockaddr_in *)&ifra.ifra_addr;
+      msk = (struct sockaddr_in *)&ifra.ifra_mask;
+      peer = (struct sockaddr_in *)&ifra.ifra_broadaddr;
+      me->sin_family = msk->sin_family = peer->sin_family = AF_INET;
+      me->sin_len = msk->sin_len = peer->sin_len = sizeof(struct sockaddr_in);
+      me->sin_addr = iface->in_addr[chg].ifa;
+      msk->sin_addr = iface->in_addr[chg].mask;
+      peer->sin_addr = iface->in_addr[chg].brd;
+      log_Printf(LogDEBUG, "Delete %s\n", inet_ntoa(me->sin_addr));
+      ID0ioctl(s, SIOCDIFADDR, &ifra);	/* Don't care if it fails... */
+      if (chg != slot) {
+        peer->sin_addr.s_addr = iface->in_addr[chg].brd.s_addr =
+          msk->sin_addr.s_addr = iface->in_addr[chg].mask.s_addr =
+            INADDR_BROADCAST;
+        iface->in_addr[chg].bits = 32;
+        log_Printf(LogDEBUG, "Add %s -> 255.255.255.255\n",
+                   inet_ntoa(me->sin_addr));
+        if (ID0ioctl(s, SIOCAIFADDR, &ifra) < 0 && errno != EEXIST) {
+          /* Oops - that's bad(ish) news !  We've lost an alias ! */
+          log_Printf(LogERROR, "iface_inAdd: ioctl(SIOCAIFADDR): %s: %s\n",
+               inet_ntoa(me->sin_addr), strerror(errno));
+          iface->in_addrs--;
+          bcopy(iface->in_addr + chg + 1, iface->in_addr + chg,
+                (iface->in_addrs - chg) * sizeof iface->in_addr[0]);
+          if (slot > chg)
+            slot--;
+          chg--;
+        }
+      }
+    }
+  }
+
   memset(&ifra, '\0', sizeof ifra);
   strncpy(ifra.ifra_name, iface->name, sizeof ifra.ifra_name - 1);
-
   me = (struct sockaddr_in *)&ifra.ifra_addr;
   msk = (struct sockaddr_in *)&ifra.ifra_mask;
   peer = (struct sockaddr_in *)&ifra.ifra_broadaddr;
-
   me->sin_family = msk->sin_family = peer->sin_family = AF_INET;
   me->sin_len = msk->sin_len = peer->sin_len = sizeof(struct sockaddr_in);
-
   me->sin_addr = ifa;
   msk->sin_addr = mask;
   peer->sin_addr = brd;
 
-  /*
-   * Note: EEXIST is sometimes returned, despite the route actually being
-   *       added !
-   */
-  if (ID0ioctl(s, SIOCAIFADDR, &ifra) < 0 && errno != EEXIST) {
-    log_Printf(LogERROR, "iface_inAdd: ioctl(SIOCAIFADDR): %s\n",
-               strerror(errno));
+  if (log_IsKept(LogDEBUG)) {
+    char buf[16];
+
+    strncpy(buf, inet_ntoa(brd), sizeof buf-1);
+    buf[sizeof buf - 1] = '\0';
+    log_Printf(LogDEBUG, "Add %s -> %s\n", inet_ntoa(ifa), buf);
+  }
+
+  /* An EEXIST failure w/ brd == INADDR_BROADCAST is ok (and works!) */
+  if (ID0ioctl(s, SIOCAIFADDR, &ifra) < 0 &&
+      (brd.s_addr != INADDR_BROADCAST || errno != EEXIST)) {
+    log_Printf(LogERROR, "iface_inAdd: ioctl(SIOCAIFADDR): %s: %s\n",
+               inet_ntoa(ifa), strerror(errno));
+    ID0ioctl(s, SIOCDIFADDR, &ifra);	/* EEXIST ? */
     close(s);
     return 0;
   }