Add install filter parameter pref_src.

The purpose is to override *locally* RTA_PREFSRC ('src' in ip-route).

babeld.man

@@ -562,6 +562,12 @@ filter, specify the kernel routing table to use.  For source-specific
 routes, this only works reliably for IPv6, and only when
 .B ipv6-subtrees
 is true.
+.TP
+.BI pref-src " ip"
+Specify the preferred source address to use with this route.  Only useful
+in an
+.B install
+filter.
 .PP
 If
 .I action

configuration.c

@@ -471,6 +471,15 @@ parse_filter(int c, gnc_t gnc, void *closure, struct filter **filter_return)
             if(table <= 0 || table > INFINITY)
                 goto error;
             filter->action.table = table;
+        } else if(strcmp(token, "pref-src") == 0) {
+            int af;
+            c = getip(c, &filter->action.pref_src, &af, gnc, closure);
+            if(c < -1)
+                goto error;
+            if(filter->af == AF_UNSPEC)
+                filter->af = af;
+            else if(filter->af != af)
+                goto error;
         } else {
             goto error;
         }
@@ -1337,11 +1346,12 @@ redistribute_filter(const unsigned char *prefix, unsigned short plen,
 int
 install_filter(const unsigned char *prefix, unsigned short plen,
                const unsigned char *src_prefix, unsigned short src_plen,
+               unsigned int ifindex,
                struct filter_result *result)
 {
     int res;
     res = do_filter(install_filters, NULL, prefix, plen,
-                    src_prefix, src_plen, NULL, 0, 0, result);
+                    src_prefix, src_plen, NULL, ifindex, 0, result);
     if(res < 0)
         res = INFINITY;
     return res;

configuration.h

@@ -34,6 +34,7 @@ struct filter_result {
     unsigned char *src_prefix;
     unsigned char src_plen;
     unsigned int table;
+    unsigned char *pref_src;
 };
 
 struct filter {
@@ -75,5 +76,5 @@ int redistribute_filter(const unsigned char *prefix, unsigned short plen,
                     struct filter_result *result);
 int install_filter(const unsigned char *prefix, unsigned short plen,
                    const unsigned char *src_prefix, unsigned short src_plen,
-                   struct filter_result *result);
+                   unsigned int ifindex, struct filter_result *result);
 int finalise_config(void);

disambiguation.c

@@ -221,17 +221,21 @@ change_route(int operation, const struct zone *zone,
              int new_ifindex, int new_metric)
 {
     struct filter_result filter_result;
+    unsigned char *pref_src = NULL;
     unsigned int ifindex = route->neigh->ifp->ifindex;
 
-    install_filter(zone->dst_prefix, zone->dst_plen,
-                   zone->src_prefix, zone->src_plen, &filter_result);
+    int m = install_filter(zone->dst_prefix, zone->dst_plen,
+                           zone->src_prefix, zone->src_plen,
+                           ifindex, &filter_result);
+    if (m < INFINITY)
+        pref_src = filter_result.pref_src;
 
     int table = filter_result.table ? filter_result.table :
         find_table(zone->dst_prefix, zone->dst_plen,
                    zone->src_prefix, zone->src_plen);
 
     return kernel_route(operation, table, zone->dst_prefix, zone->dst_plen,
-                        zone->src_prefix, zone->src_plen,
+                        zone->src_prefix, zone->src_plen, pref_src,
                         route->nexthop, ifindex,
                         metric, new_next_hop, new_ifindex, new_metric,
                         operation == ROUTE_MODIFY ? table : 0);

kernel.h

@@ -94,6 +94,7 @@ int kernel_disambiguate(int v4);
 int kernel_route(int operation, int table,
                  const unsigned char *dest, unsigned short plen,
                  const unsigned char *src, unsigned short src_plen,
+                 const unsigned char *pref_src,
                  const unsigned char *gate, int ifindex, unsigned int metric,
                  const unsigned char *newgate, int newifindex,
                  unsigned int newmetric, int newtable);

kernel_netlink.c

@@ -944,6 +944,7 @@ int
 kernel_route(int operation, int table,
              const unsigned char *dest, unsigned short plen,
              const unsigned char *src, unsigned short src_plen,
+             const unsigned char *pref_src,
              const unsigned char *gate, int ifindex, unsigned int metric,
              const unsigned char *newgate, int newifindex,
              unsigned int newmetric, int newtable)
@@ -997,11 +998,11 @@ kernel_route(int operation, int table,
            stick with the naive approach, and hope that the window is
            small enough to be negligible. */
         kernel_route(ROUTE_FLUSH, table, dest, plen,
-                     src, src_plen,
+                     src, src_plen, pref_src,
                      gate, ifindex, metric,
                      NULL, 0, 0, 0);
         rc = kernel_route(ROUTE_ADD, newtable, dest, plen,
-                          src, src_plen,
+                          src, src_plen, pref_src,
                           newgate, newifindex, newmetric,
                           NULL, 0, 0, 0);
         if(rc < 0) {
@@ -1084,17 +1085,24 @@ kernel_route(int operation, int table,
         rta->rta_type = RTA_OIF;
         *(int*)RTA_DATA(rta) = ifindex;
 
-        if(ipv4) {
-            rta = RTA_NEXT(rta, len);
-            rta->rta_len = RTA_LENGTH(sizeof(struct in_addr));
-            rta->rta_type = RTA_GATEWAY;
-            memcpy(RTA_DATA(rta), gate + 12, sizeof(struct in_addr));
-        } else {
-            rta = RTA_NEXT(rta, len);
-            rta->rta_len = RTA_LENGTH(sizeof(struct in6_addr));
-            rta->rta_type = RTA_GATEWAY;
-            memcpy(RTA_DATA(rta), gate, sizeof(struct in6_addr));
-        }
+#define ADD_IPARG(type, addr) \
+        do if(ipv4) { \
+            rta = RTA_NEXT(rta, len); \
+            rta->rta_len = RTA_LENGTH(sizeof(struct in_addr)); \
+            rta->rta_type = type; \
+            memcpy(RTA_DATA(rta), addr + 12, sizeof(struct in_addr)); \
+        } else { \
+            rta = RTA_NEXT(rta, len); \
+            rta->rta_len = RTA_LENGTH(sizeof(struct in6_addr)); \
+            rta->rta_type = type; \
+            memcpy(RTA_DATA(rta), addr, sizeof(struct in6_addr)); \
+        } while (0)
+
+        ADD_IPARG(RTA_GATEWAY, gate);
+        if(pref_src)
+            ADD_IPARG(RTA_PREFSRC, pref_src);
+
+#undef ADD_IPARG
     } else {
         *(int*)RTA_DATA(rta) = -1;
     }

kernel_socket.c

@@ -408,6 +408,7 @@ int
 kernel_route(int operation, int table,
              const unsigned char *dest, unsigned short plen,
              const unsigned char *src, unsigned short src_plen,
+             const unsigned char *pref_src,
              const unsigned char *gate, int ifindex, unsigned int metric,
              const unsigned char *newgate, int newifindex,
              unsigned int newmetric, int newtable)
@@ -424,8 +425,9 @@ kernel_route(int operation, int table,
         {{{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
             0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x01 }}};
 
-    /* Source-specific routes are not implemented yet for BSD. */
-    if(!is_default(src, src_plen)) {
+    /* Source-specific routes & preferred source IPs
+     * are not implemented yet for BSD. */
+    if((!is_default(src, src_plen)) || pref_src) {
         errno = ENOSYS;
         return -1;
     }