[XFRM]: IPsec tunnel wildcard address support

When the source address of a tunnel is given as 0.0.0.0 do a routing lookup
to get the real source address for the destination and fill that into the
acquire message. This allows to specify policies like this:

spdadd 172.16.128.13/32 172.16.0.0/20 any -P out ipsec
        esp/tunnel/0.0.0.0-x.x.x.x/require;
spdadd 172.16.0.0/20 172.16.128.13/32 any -P in ipsec
        esp/tunnel/x.x.x.x-0.0.0.0/require;

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 32 insertions, 0 deletions

diff --git a/net/ipv4/xfrm4_state.c b/net/ipv4/xfrm4_state.c
index d23e07fc81fa..dbabf81a9b7b 100644
--- a/net/ipv4/xfrm4_state.c
+++ b/net/ipv4/xfrm4_state.c
@@ -42,6 +42,21 @@ __xfrm4_init_tempsel(struct xfrm_state *x, struct flowi *fl,
         x->props.saddr = tmpl->saddr;
         if (x->props.saddr.a4 == 0)
                 x->props.saddr.a4 = saddr->a4;
+        if (tmpl->mode && x->props.saddr.a4 == 0) {
+                struct rtable *rt;
+                struct flowi fl_tunnel = {
+                        .nl_u = {
+                                .ip4_u = {
+                                        .daddr = x->id.daddr.a4,
+                                }
+                        }
+                };
+                if (!xfrm_dst_lookup((struct xfrm_dst **)&rt,
+                                     &fl_tunnel, AF_INET)) {
+                        x->props.saddr.a4 = rt->rt_src;
+                        dst_release(&rt->u.dst);
+                }
+        }
         x->props.mode = tmpl->mode;
         x->props.reqid = tmpl->reqid;
         x->props.family = AF_INET;
diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
index bf0d0abc3871..a5723024d3b3 100644
--- a/net/ipv6/xfrm6_state.c
+++ b/net/ipv6/xfrm6_state.c
@@ -15,6 +15,7 @@
 #include <linux/pfkeyv2.h>
 #include <linux/ipsec.h>
 #include <net/ipv6.h>
+#include <net/addrconf.h>
 
 static struct xfrm_state_afinfo xfrm6_state_afinfo;
 
@@ -41,6 +42,22 @@ __xfrm6_init_tempsel(struct xfrm_state *x, struct flowi *fl,
         memcpy(&x->props.saddr, &tmpl->saddr, sizeof(x->props.saddr));
         if (ipv6_addr_any((struct in6_addr*)&x->props.saddr))
                 memcpy(&x->props.saddr, saddr, sizeof(x->props.saddr));
+        if (tmpl->mode && ipv6_addr_any((struct in6_addr*)&x->props.saddr)) {
+                struct rt6_info *rt;
+                struct flowi fl_tunnel = {
+                        .nl_u = {
+                                .ip6_u = {
+                                        .daddr = *(struct in6_addr *)daddr,
+                                }
+                        }
+                };
+                if (!xfrm_dst_lookup((struct xfrm_dst **)&rt,
+                                     &fl_tunnel, AF_INET6)) {
+                        ipv6_get_saddr(&rt->u.dst, (struct in6_addr *)daddr,
+                                       (struct in6_addr *)&x->props.saddr);
+                        dst_release(&rt->u.dst);
+                }
+        }
         x->props.mode = tmpl->mode;
         x->props.reqid = tmpl->reqid;
         x->props.family = AF_INET6;