This patch does the following:

    - Allow loopback route to be installed for address assigned to
      interface of IFF_POINTOPOINT type.
    - Install loopback route for an IPv4 interface addreess when the
      "useloopback" sysctl variable is enabled. Similarly, install
      loopback route for an IPv6 interface address when the sysctl variable
      "nd6_useloopback" is enabled. Deleting loopback routes for interface
      addresses is unconditional in case these sysctl variables were
      disabled after an interface address has been assigned.

Reviewed by:	bz
Approved by:	re

2 files changed, 16 insertions, 5 deletions

diff --git a/sys/netinet/if_ether.c b/sys/netinet/if_ether.c
index 6b6b5e6..e64b21f 100644
--- a/sys/netinet/if_ether.c
+++ b/sys/netinet/if_ether.c
@@ -81,17 +81,17 @@ __FBSDID("$FreeBSD$");
 SYSCTL_DECL(_net_link_ether);
 SYSCTL_NODE(_net_link_ether, PF_INET, inet, CTLFLAG_RW, 0, "");
 
+VNET_DEFINE(int, useloopback) = 1;	/* use loopback interface for
+					 * local traffic */
+
 /* timer values */
 static VNET_DEFINE(int, arpt_keep) = (20*60);	/* once resolved, good for 20
 						 * minutes */
 static VNET_DEFINE(int, arp_maxtries) = 5;
-static VNET_DEFINE(int, useloopback) = 1;	/* use loopback interface for
-						 * local traffic */
 static VNET_DEFINE(int, arp_proxyall);
 
 #define	V_arpt_keep		VNET(arpt_keep)
 #define	V_arp_maxtries		VNET(arp_maxtries)
-#define	V_useloopback		VNET(useloopback)
 #define	V_arp_proxyall		VNET(arp_proxyall)
 
 SYSCTL_VNET_INT(_net_link_ether_inet, OID_AUTO, max_age, CTLFLAG_RW,
diff --git a/sys/netinet/in.c b/sys/netinet/in.c
index a606562..63a712b 100644
--- a/sys/netinet/in.c
+++ b/sys/netinet/in.c
@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/vimage.h>
 
 #include <net/if.h>
+#include <net/if_var.h>
 #include <net/if_dl.h>
 #include <net/if_llatbl.h>
 #include <net/if_types.h>
@@ -918,7 +919,7 @@ in_ifinit(struct ifnet *ifp, struct in_ifaddr *ia, struct sockaddr_in *sin,
 	/*
 	 * add a loopback route to self
 	 */
-	if (!(ifp->if_flags & (IFF_LOOPBACK | IFF_POINTOPOINT))) {
+	if (V_useloopback && !(ifp->if_flags & IFF_LOOPBACK)) {
 		bzero(&info, sizeof(info));
 		info.rti_ifp = V_loif;
 		info.rti_flags = ia->ia_flags | RTF_HOST | RTF_STATIC;
@@ -1027,8 +1028,18 @@ in_scrubprefix(struct in_ifaddr *target)
 	if ((target->ia_flags & IFA_ROUTE) == 0)
 		return (0);
 
+	/*
+	 * Remove the loopback route to the interface address.
+	 * The "useloopback" setting is not consulted because if the
+	 * user configures an interface address, turns off this
+	 * setting, and then tries to delete that interface address,
+	 * checking the current setting of "useloopback" would leave
+	 * that interface address loopback route untouched, which
+	 * would be wrong. Therefore the interface address loopback route
+	 * deletion is unconditional.
+	 */
 	if ((target->ia_addr.sin_addr.s_addr != INADDR_ANY) &&
-	    !(target->ia_ifp->if_flags & (IFF_LOOPBACK | IFF_POINTOPOINT))) {
+	    !(target->ia_ifp->if_flags & IFF_LOOPBACK)) {
 		bzero(&null_sdl, sizeof(null_sdl));
 		null_sdl.sdl_len = sizeof(null_sdl);
 		null_sdl.sdl_family = AF_LINK;