Adding upstream version 8.4.4.upstream/8.4.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1146 insertions, 0 deletions

diff --git a/babeld/route.c b/babeld/route.c
new file mode 100644
index 0000000..8dd1e40
--- /dev/null
+++ b/babeld/route.c
@@ -0,0 +1,1146 @@
+/*
+Copyright (c) 2007, 2008 by Juliusz Chroboczek
+Copyright 2011 by Matthieu Boutier and Juliusz Chroboczek
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+
+#include <zebra.h>
+#include "if.h"
+
+#include "babeld.h"
+#include "util.h"
+#include "kernel.h"
+#include "babel_interface.h"
+#include "source.h"
+#include "neighbour.h"
+#include "route.h"
+#include "xroute.h"
+#include "message.h"
+#include "resend.h"
+#include "babel_errors.h"
+
+static void consider_route(struct babel_route *route);
+
+struct babel_route **routes = NULL;
+static int route_slots = 0, max_route_slots = 0;
+int kernel_metric = 0;
+enum babel_diversity diversity_kind = DIVERSITY_NONE;
+int diversity_factor = BABEL_DEFAULT_DIVERSITY_FACTOR;
+int keep_unfeasible = 0;
+
+int smoothing_half_life = 0;
+static int two_to_the_one_over_hl = 0; /* 2^(1/hl) * 0x10000 */
+
+/* We maintain a list of "slots", ordered by prefix.  Every slot
+   contains a linked list of the routes to this prefix, with the
+   installed route, if any, at the head of the list. */
+
+static int
+route_compare(const unsigned char *prefix, unsigned char plen,
+               struct babel_route *route)
+{
+    int i = memcmp(prefix, route->src->prefix, 16);
+    if(i != 0)
+        return i;
+
+    if(plen < route->src->plen)
+        return -1;
+    else if(plen > route->src->plen)
+        return 1;
+    else
+        return 0;
+}
+
+/* Performs binary search, returns -1 in case of failure.  In the latter
+   case, new_return is the place where to insert the new element. */
+
+static int
+find_route_slot(const unsigned char *prefix, unsigned char plen,
+                int *new_return)
+{
+    int p, m, g, c;
+
+    if(route_slots < 1) {
+        if(new_return)
+            *new_return = 0;
+        return -1;
+    }
+
+    p = 0; g = route_slots - 1;
+
+    do {
+        m = (p + g) / 2;
+        c = route_compare(prefix, plen, routes[m]);
+        if(c == 0)
+            return m;
+        else if(c < 0)
+            g = m - 1;
+        else
+            p = m + 1;
+    } while(p <= g);
+
+    if(new_return)
+        *new_return = p;
+
+    return -1;
+}
+
+struct babel_route *
+find_route(const unsigned char *prefix, unsigned char plen,
+           struct neighbour *neigh, const unsigned char *nexthop)
+{
+    struct babel_route *route;
+    int i = find_route_slot(prefix, plen, NULL);
+
+    if(i < 0)
+        return NULL;
+
+    route = routes[i];
+
+    while(route) {
+        if(route->neigh == neigh && memcmp(route->nexthop, nexthop, 16) == 0)
+            return route;
+        route = route->next;
+    }
+
+    return NULL;
+}
+
+struct babel_route *
+find_installed_route(const unsigned char *prefix, unsigned char plen)
+{
+    int i = find_route_slot(prefix, plen, NULL);
+
+    if(i >= 0 && routes[i]->installed)
+        return routes[i];
+
+    return NULL;
+}
+
+/* Returns an overestimate of the number of installed routes. */
+int
+installed_routes_estimate(void)
+{
+    return route_slots;
+}
+
+static int
+resize_route_table(int new_slots)
+{
+    struct babel_route **new_routes;
+    assert(new_slots >= route_slots);
+
+    if(new_slots == 0) {
+        new_routes = NULL;
+        free(routes);
+    } else {
+        new_routes = realloc(routes, new_slots * sizeof(struct babel_route*));
+        if(new_routes == NULL)
+            return -1;
+    }
+
+    max_route_slots = new_slots;
+    routes = new_routes;
+    return 1;
+}
+
+/* Insert a route into the table.  If successful, retains the route.
+   On failure, caller must free the route. */
+static struct babel_route *
+insert_route(struct babel_route *route)
+{
+    int i, n = 0;
+
+    assert(!route->installed);
+
+    i = find_route_slot(route->src->prefix, route->src->plen, &n);
+
+    if(i < 0) {
+        if(route_slots >= max_route_slots)
+            resize_route_table(max_route_slots < 1 ? 8 : 2 * max_route_slots);
+        if(route_slots >= max_route_slots)
+            return NULL;
+        assert(routes);
+        route->next = NULL;
+        if(n < route_slots)
+            memmove(routes + n + 1, routes + n,
+                    (route_slots - n) * sizeof(struct babel_route*));
+        route_slots++;
+        routes[n] = route;
+    } else {
+        struct babel_route *r;
+        r = routes[i];
+        while(r->next)
+            r = r->next;
+        r->next = route;
+        route->next = NULL;
+    }
+
+    return route;
+}
+
+void
+flush_route(struct babel_route *route)
+{
+    int i;
+    struct source *src;
+    unsigned oldmetric;
+    int lost = 0;
+
+    oldmetric = route_metric(route);
+    src = route->src;
+
+    if(route->installed) {
+        uninstall_route(route);
+        lost = 1;
+    }
+
+    i = find_route_slot(route->src->prefix, route->src->plen, NULL);
+    assert(i >= 0 && i < route_slots);
+
+    if(route == routes[i]) {
+        routes[i] = route->next;
+        route->next = NULL;
+        free(route);
+
+        if(routes[i] == NULL) {
+            if(i < route_slots - 1)
+                memmove(routes + i, routes + i + 1,
+                        (route_slots - i - 1) * sizeof(struct babel_route*));
+            routes[route_slots - 1] = NULL;
+            route_slots--;
+        }
+
+        if(route_slots == 0)
+            resize_route_table(0);
+        else if(max_route_slots > 8 && route_slots < max_route_slots / 4)
+            resize_route_table(max_route_slots / 2);
+    } else {
+        struct babel_route *r = routes[i];
+        while(r->next != route)
+            r = r->next;
+        r->next = route->next;
+        route->next = NULL;
+        free(route);
+    }
+
+    if(lost)
+        route_lost(src, oldmetric);
+
+    release_source(src);
+}
+
+void
+flush_all_routes(void)
+{
+    int i;
+
+    /* Start from the end, to avoid shifting the table. */
+    i = route_slots - 1;
+    while(i >= 0) {
+        while(i < route_slots) {
+        /* Uninstall first, to avoid calling route_lost. */
+            if(routes[i]->installed)
+                uninstall_route(routes[i]);
+            flush_route(routes[i]);
+        }
+        i--;
+    }
+
+    check_sources_released();
+}
+
+void
+flush_neighbour_routes(struct neighbour *neigh)
+{
+    int i;
+
+    i = 0;
+    while(i < route_slots) {
+        struct babel_route *r;
+        r = routes[i];
+        while(r) {
+            if(r->neigh == neigh) {
+                flush_route(r);
+                goto again;
+            }
+            r = r->next;
+        }
+        i++;
+    again:
+        ;
+    }
+}
+
+void
+flush_interface_routes(struct interface *ifp, int v4only)
+{
+    int i;
+
+    i = 0;
+    while(i < route_slots) {
+        struct babel_route *r;
+        r = routes[i];
+        while(r) {
+            if(r->neigh->ifp == ifp &&
+               (!v4only || v4mapped(r->nexthop))) {
+                flush_route(r);
+                goto again;
+            }
+            r = r->next;
+        }
+        i++;
+    again:
+        ;
+    }
+}
+
+struct route_stream {
+    int installed;
+    int index;
+    struct babel_route *next;
+};
+
+
+struct route_stream *
+route_stream(int installed)
+{
+    struct route_stream *stream;
+
+    stream = malloc(sizeof(struct route_stream));
+    if(stream == NULL)
+       return NULL;
+
+    stream->installed = installed;
+    stream->index = installed ? 0 : -1;
+    stream->next = NULL;
+
+    return stream;
+}
+
+struct babel_route *
+route_stream_next(struct route_stream *stream)
+{
+    if(stream->installed) {
+        while(stream->index < route_slots && !routes[stream->index]->installed)
+            stream->index++;
+
+        if(stream->index < route_slots)
+            return routes[stream->index++];
+        else
+            return NULL;
+    } else {
+        struct babel_route *next;
+        if(!stream->next) {
+            stream->index++;
+            if(stream->index >= route_slots)
+                return NULL;
+            stream->next = routes[stream->index];
+        }
+        next = stream->next;
+        stream->next = next->next;
+        return next;
+    }
+}
+
+void
+route_stream_done(struct route_stream *stream)
+{
+    free(stream);
+}
+
+static int
+metric_to_kernel(int metric)
+{
+    return metric < INFINITY ? kernel_metric : KERNEL_INFINITY;
+}
+
+/* This is used to maintain the invariant that the installed route is at
+   the head of the list. */
+static void
+move_installed_route(struct babel_route *route, int i)
+{
+    assert(i >= 0 && i < route_slots);
+    assert(route->installed);
+
+    if(route != routes[i]) {
+        struct babel_route *r = routes[i];
+        while(r->next != route)
+            r = r->next;
+        r->next = route->next;
+        route->next = routes[i];
+        routes[i] = route;
+    }
+}
+
+void
+install_route(struct babel_route *route)
+{
+    int i, rc;
+
+    if(route->installed)
+        return;
+
+    if(!route_feasible(route))
+	    flog_err(EC_BABEL_ROUTE,
+		     "Installing unfeasible route (this shouldn't happen).");
+
+    i = find_route_slot(route->src->prefix, route->src->plen, NULL);
+    assert(i >= 0 && i < route_slots);
+
+    if(routes[i] != route && routes[i]->installed) {
+	    flog_err(
+		    EC_BABEL_ROUTE,
+		    "Attempting to install duplicate route (this shouldn't happen).");
+	    return;
+    }
+
+    rc = kernel_route(ROUTE_ADD, route->src->prefix, route->src->plen,
+                      route->nexthop,
+                      route->neigh->ifp->ifindex,
+                      metric_to_kernel(route_metric(route)), NULL, 0, 0);
+    if(rc < 0) {
+        int save = errno;
+        flog_err(EC_BABEL_ROUTE, "kernel_route(ADD): %s",
+		  safe_strerror(errno));
+        if(save != EEXIST)
+            return;
+    }
+    route->installed = 1;
+    move_installed_route(route, i);
+
+}
+
+void
+uninstall_route(struct babel_route *route)
+{
+    int rc;
+
+    if(!route->installed)
+        return;
+
+    rc = kernel_route(ROUTE_FLUSH, route->src->prefix, route->src->plen,
+                      route->nexthop,
+                      route->neigh->ifp->ifindex,
+                      metric_to_kernel(route_metric(route)), NULL, 0, 0);
+    if(rc < 0)
+        flog_err(EC_BABEL_ROUTE, "kernel_route(FLUSH): %s",
+		  safe_strerror(errno));
+
+    route->installed = 0;
+}
+
+/* This is equivalent to uninstall_route followed with install_route,
+   but without the race condition.  The destination of both routes
+   must be the same. */
+
+static void
+switch_routes(struct babel_route *old, struct babel_route *new)
+{
+    int rc;
+
+    if(!old) {
+        install_route(new);
+        return;
+    }
+
+    if(!old->installed)
+        return;
+
+    if(!route_feasible(new))
+	    flog_err(EC_BABEL_ROUTE,
+		     "Switching to unfeasible route (this shouldn't happen).");
+
+    rc = kernel_route(ROUTE_MODIFY, old->src->prefix, old->src->plen,
+                      old->nexthop, old->neigh->ifp->ifindex,
+                      metric_to_kernel(route_metric(old)),
+                      new->nexthop, new->neigh->ifp->ifindex,
+                      metric_to_kernel(route_metric(new)));
+    if(rc < 0) {
+        flog_err(EC_BABEL_ROUTE, "kernel_route(MODIFY): %s",
+		  safe_strerror(errno));
+        return;
+    }
+
+    old->installed = 0;
+    new->installed = 1;
+    move_installed_route(new, find_route_slot(new->src->prefix, new->src->plen,
+                                              NULL));
+}
+
+static void
+change_route_metric(struct babel_route *route,
+                    unsigned refmetric, unsigned cost, unsigned add)
+{
+    int old, new;
+    int newmetric = MIN(refmetric + cost + add, INFINITY);
+
+    old = metric_to_kernel(route_metric(route));
+    new = metric_to_kernel(newmetric);
+
+    if(route->installed && old != new) {
+        int rc;
+        rc = kernel_route(ROUTE_MODIFY, route->src->prefix, route->src->plen,
+                          route->nexthop, route->neigh->ifp->ifindex,
+                          old,
+                          route->nexthop, route->neigh->ifp->ifindex,
+                          new);
+        if(rc < 0) {
+            flog_err(EC_BABEL_ROUTE, "kernel_route(MODIFY metric): %s",
+		      safe_strerror(errno));
+            return;
+        }
+    }
+
+    /* Update route->smoothed_metric using the old metric. */
+    route_smoothed_metric(route);
+
+    route->refmetric = refmetric;
+    route->cost = cost;
+    route->add_metric = add;
+
+    if(smoothing_half_life == 0) {
+        route->smoothed_metric = route_metric(route);
+        route->smoothed_metric_time = babel_now.tv_sec;
+    }
+}
+
+static void
+retract_route(struct babel_route *route)
+{
+    /* We cannot simply remove the route from the kernel, as that might
+       cause a routing loop -- see RFC 6126 Sections 2.8 and 3.5.5. */
+    change_route_metric(route, INFINITY, INFINITY, 0);
+}
+
+int
+route_feasible(struct babel_route *route)
+{
+    return update_feasible(route->src, route->seqno, route->refmetric);
+}
+
+int
+route_old(struct babel_route *route)
+{
+    return route->time < babel_now.tv_sec - route->hold_time * 7 / 8;
+}
+
+int
+route_expired(struct babel_route *route)
+{
+    return route->time < babel_now.tv_sec - route->hold_time;
+}
+
+static int
+channels_interfere(int ch1, int ch2)
+{
+    if(ch1 == BABEL_IF_CHANNEL_NONINTERFERING
+       || ch2 == BABEL_IF_CHANNEL_NONINTERFERING)
+        return 0;
+    if(ch1 == BABEL_IF_CHANNEL_INTERFERING
+       || ch2 == BABEL_IF_CHANNEL_INTERFERING)
+        return 1;
+    return ch1 == ch2;
+}
+
+int
+route_interferes(struct babel_route *route, struct interface *ifp)
+{
+    struct babel_interface *babel_ifp = NULL;
+    switch(diversity_kind) {
+    case DIVERSITY_NONE:
+        return 1;
+    case DIVERSITY_INTERFACE_1:
+        return route->neigh->ifp == ifp;
+    case DIVERSITY_CHANNEL_1:
+    case DIVERSITY_CHANNEL:
+        if(route->neigh->ifp == ifp)
+            return 1;
+        babel_ifp = babel_get_if_nfo(ifp);
+        if(channels_interfere(babel_ifp->channel,
+                              babel_get_if_nfo(route->neigh->ifp)->channel))
+            return 1;
+        if(diversity_kind == DIVERSITY_CHANNEL) {
+            int i;
+            for(i = 0; i < DIVERSITY_HOPS; i++) {
+                if(route->channels[i] == 0)
+                    break;
+                if(channels_interfere(babel_ifp->channel, route->channels[i]))
+                    return 1;
+            }
+        }
+        return 0;
+    }
+
+    return 1;
+}
+
+int
+update_feasible(struct source *src,
+                unsigned short seqno, unsigned short refmetric)
+{
+    if(src == NULL)
+        return 1;
+
+    if(src->time < babel_now.tv_sec - SOURCE_GC_TIME)
+        /* Never mind what is probably stale data */
+        return 1;
+
+    if(refmetric >= INFINITY)
+        /* Retractions are always feasible */
+        return 1;
+
+    return (seqno_compare(seqno, src->seqno) > 0 ||
+            (src->seqno == seqno && refmetric < src->metric));
+}
+
+void
+change_smoothing_half_life(int half_life)
+{
+    if(half_life <= 0) {
+        smoothing_half_life = 0;
+        two_to_the_one_over_hl = 0;
+        return;
+    }
+
+    smoothing_half_life = half_life;
+    switch(smoothing_half_life) {
+    case 1: two_to_the_one_over_hl = 131072; break;
+    case 2: two_to_the_one_over_hl = 92682; break;
+    case 3: two_to_the_one_over_hl = 82570; break;
+    case 4: two_to_the_one_over_hl = 77935; break;
+    default:
+        /* 2^(1/x) is 1 + log(2)/x + O(1/x^2) at infinity. */
+        two_to_the_one_over_hl = 0x10000 + 45426 / half_life;
+    }
+}
+
+/* Update the smoothed metric, return the new value. */
+int
+route_smoothed_metric(struct babel_route *route)
+{
+    int metric = route_metric(route);
+
+    if(smoothing_half_life <= 0 ||                 /* no smoothing */
+       metric >= INFINITY ||                       /* route retracted */
+       route->smoothed_metric_time > babel_now.tv_sec || /* clock stepped */
+       route->smoothed_metric == metric) {         /* already converged */
+        route->smoothed_metric = metric;
+        route->smoothed_metric_time = babel_now.tv_sec;
+    } else {
+        int diff;
+        /* We randomise the computation, to minimise global synchronisation
+           and hence oscillations. */
+        while(route->smoothed_metric_time <=
+              babel_now.tv_sec - smoothing_half_life) {
+            diff = metric - route->smoothed_metric;
+            route->smoothed_metric += roughly(diff) / 2;
+            route->smoothed_metric_time += smoothing_half_life;
+        }
+        while(route->smoothed_metric_time < babel_now.tv_sec) {
+            diff = metric - route->smoothed_metric;
+            route->smoothed_metric +=
+                roughly(diff) * (two_to_the_one_over_hl - 0x10000) / 0x10000;
+            route->smoothed_metric_time++;
+        }
+
+        diff = metric - route->smoothed_metric;
+        if(diff > -4 && diff < 4)
+            route->smoothed_metric = metric;
+    }
+
+    /* change_route_metric relies on this */
+    assert(route->smoothed_metric_time == babel_now.tv_sec);
+    return route->smoothed_metric;
+}
+
+static int
+route_acceptable(struct babel_route *route, int feasible,
+                 struct neighbour *exclude)
+{
+    if(route_expired(route))
+        return 0;
+    if(feasible && !route_feasible(route))
+        return 0;
+    if(exclude && route->neigh == exclude)
+        return 0;
+    return 1;
+}
+
+/* Find the best route according to the weak ordering.  Any
+   linearisation of the strong ordering (see consider_route) will do,
+   we use sm <= sm'.  We could probably use a lexical ordering, but
+   that's probably overkill. */
+
+struct babel_route *
+find_best_route(const unsigned char *prefix, unsigned char plen, int feasible,
+                struct neighbour *exclude)
+{
+    struct babel_route *route = NULL, *r = NULL;
+    int i = find_route_slot(prefix, plen, NULL);
+
+    if(i < 0)
+        return NULL;
+
+    route = routes[i];
+    while(route && !route_acceptable(route, feasible, exclude))
+        route = route->next;
+
+    if(!route)
+        return NULL;
+
+    r = route->next;
+    while(r) {
+        if(route_acceptable(r, feasible, exclude) &&
+           (route_smoothed_metric(r) < route_smoothed_metric(route)))
+            route = r;
+        r = r->next;
+    }
+
+    return route;
+}
+
+void
+update_route_metric(struct babel_route *route)
+{
+    int oldmetric = route_metric(route);
+    int old_smoothed_metric = route_smoothed_metric(route);
+
+    if(route_expired(route)) {
+        if(route->refmetric < INFINITY) {
+            route->seqno = seqno_plus(route->src->seqno, 1);
+            retract_route(route);
+            if(oldmetric < INFINITY)
+                route_changed(route, route->src, oldmetric);
+        }
+    } else {
+        struct neighbour *neigh = route->neigh;
+        int add_metric = input_filter(route->src->id,
+                                      route->src->prefix, route->src->plen,
+                                      neigh->address,
+                                      neigh->ifp->ifindex);
+        change_route_metric(route, route->refmetric,
+                            neighbour_cost(route->neigh), add_metric);
+        if(route_metric(route) != oldmetric ||
+           route_smoothed_metric(route) != old_smoothed_metric)
+            route_changed(route, route->src, oldmetric);
+    }
+}
+
+/* Called whenever a neighbour's cost changes, to update the metric of
+   all routes through that neighbour. */
+void
+update_neighbour_metric(struct neighbour *neigh, int changed)
+{
+
+    if(changed) {
+        int i;
+
+        for(i = 0; i < route_slots; i++) {
+            struct babel_route *r = routes[i];
+            while(r) {
+                if(r->neigh == neigh)
+                    update_route_metric(r);
+                r = r->next;
+            }
+        }
+    }
+}
+
+void
+update_interface_metric(struct interface *ifp)
+{
+    int i;
+
+    for(i = 0; i < route_slots; i++) {
+        struct babel_route *r = routes[i];
+        while(r) {
+            if(r->neigh->ifp == ifp)
+                update_route_metric(r);
+            r = r->next;
+        }
+    }
+}
+
+/* This is called whenever we receive an update. */
+struct babel_route *
+update_route(const unsigned char *router_id,
+             const unsigned char *prefix, unsigned char plen,
+             unsigned short seqno, unsigned short refmetric,
+             unsigned short interval,
+             struct neighbour *neigh, const unsigned char *nexthop,
+             const unsigned char *channels, int channels_len)
+{
+    struct babel_route *route;
+    struct source *src;
+    int metric, feasible;
+    int add_metric;
+    int hold_time = MAX((4 * interval) / 100 + interval / 50, 15);
+
+    if(memcmp(router_id, myid, 8) == 0)
+        return NULL;
+
+    if(martian_prefix(prefix, plen)) {
+        flog_err(EC_BABEL_ROUTE, "Rejecting martian route to %s through %s.",
+                 format_prefix(prefix, plen), format_address(nexthop));
+        return NULL;
+    }
+
+    add_metric = input_filter(router_id, prefix, plen,
+                              neigh->address, neigh->ifp->ifindex);
+    if(add_metric >= INFINITY)
+        return NULL;
+
+    route = find_route(prefix, plen, neigh, nexthop);
+
+    if(route && memcmp(route->src->id, router_id, 8) == 0)
+        /* Avoid scanning the source table. */
+        src = route->src;
+    else
+        src = find_source(router_id, prefix, plen, 1, seqno);
+
+    if(src == NULL)
+        return NULL;
+
+    feasible = update_feasible(src, seqno, refmetric);
+    metric = MIN((int)refmetric + neighbour_cost(neigh) + add_metric, INFINITY);
+
+    if(route) {
+        struct source *oldsrc;
+        unsigned short oldmetric;
+        int lost = 0;
+
+        oldsrc = route->src;
+        oldmetric = route_metric(route);
+
+        /* If a successor switches sources, we must accept his update even
+           if it makes a route unfeasible in order to break any routing loops
+           in a timely manner.  If the source remains the same, we ignore
+           the update. */
+        if(!feasible && route->installed) {
+            debugf(BABEL_DEBUG_COMMON,"Unfeasible update for installed route to %s (%s %d %d -> %s %d %d).",
+                   format_prefix(src->prefix, src->plen),
+                   format_eui64(route->src->id),
+                   route->seqno, route->refmetric,
+                   format_eui64(src->id), seqno, refmetric);
+            if(src != route->src) {
+                uninstall_route(route);
+                lost = 1;
+            }
+        }
+
+        route->src = retain_source(src);
+        if((feasible || keep_unfeasible) && refmetric < INFINITY)
+            route->time = babel_now.tv_sec;
+        route->seqno = seqno;
+
+        memset(&route->channels, 0, sizeof(route->channels));
+        if(channels_len > 0)
+            memcpy(&route->channels, channels,
+                   MIN(channels_len, DIVERSITY_HOPS));
+
+        change_route_metric(route,
+                            refmetric, neighbour_cost(neigh), add_metric);
+        route->hold_time = hold_time;
+
+        route_changed(route, oldsrc, oldmetric);
+        if(lost)
+            route_lost(oldsrc, oldmetric);
+
+        if(!feasible)
+            send_unfeasible_request(neigh, route->installed && route_old(route),
+                                    seqno, metric, src);
+        release_source(oldsrc);
+    } else {
+        struct babel_route *new_route;
+
+        if(refmetric >= INFINITY)
+            /* Somebody's retracting a route we never saw. */
+            return NULL;
+        if(!feasible) {
+            send_unfeasible_request(neigh, 0, seqno, metric, src);
+            if(!keep_unfeasible)
+                return NULL;
+        }
+
+        route = malloc(sizeof(struct babel_route));
+        if(route == NULL) {
+            perror("malloc(route)");
+            return NULL;
+        }
+
+        route->src = retain_source(src);
+        route->refmetric = refmetric;
+        route->cost = neighbour_cost(neigh);
+        route->add_metric = add_metric;
+        route->seqno = seqno;
+        route->neigh = neigh;
+        memcpy(route->nexthop, nexthop, 16);
+        route->time = babel_now.tv_sec;
+        route->hold_time = hold_time;
+        route->smoothed_metric = MAX(route_metric(route), INFINITY / 2);
+        route->smoothed_metric_time = babel_now.tv_sec;
+        route->installed = 0;
+        memset(&route->channels, 0, sizeof(route->channels));
+        if(channels_len > 0)
+            memcpy(&route->channels, channels,
+                   MIN(channels_len, DIVERSITY_HOPS));
+        route->next = NULL;
+        new_route = insert_route(route);
+        if(new_route == NULL) {
+            flog_err(EC_BABEL_ROUTE, "Couldn't insert route.");
+            free(route);
+            return NULL;
+        }
+        consider_route(route);
+    }
+    return route;
+}
+
+/* We just received an unfeasible update.  If it's any good, send
+   a request for a new seqno. */
+void
+send_unfeasible_request(struct neighbour *neigh, int force,
+                        unsigned short seqno, unsigned short metric,
+                        struct source *src)
+{
+    struct babel_route *route = find_installed_route(src->prefix, src->plen);
+
+    if(seqno_minus(src->seqno, seqno) > 100) {
+        /* Probably a source that lost its seqno.  Let it time-out. */
+        return;
+    }
+
+    if(force || !route || route_metric(route) >= metric + 512) {
+        send_unicast_multihop_request(neigh, src->prefix, src->plen,
+                                      src->metric >= INFINITY ?
+                                      src->seqno :
+                                      seqno_plus(src->seqno, 1),
+                                      src->id, 127);
+    }
+}
+
+/* This takes a feasible route and decides whether to install it.
+   This uses the strong ordering, which is defined by sm <= sm' AND
+   m <= m'.  This ordering is not total, which is what causes
+   hysteresis. */
+
+static void
+consider_route(struct babel_route *route)
+{
+    struct babel_route *installed;
+    struct xroute *xroute;
+
+    if(route->installed)
+        return;
+
+    if(!route_feasible(route))
+        return;
+
+    xroute = find_xroute(route->src->prefix, route->src->plen);
+    if(xroute)
+        return;
+
+    installed = find_installed_route(route->src->prefix, route->src->plen);
+
+    if(installed == NULL)
+        goto install;
+
+    if(route_metric(route) >= INFINITY)
+        return;
+
+    if(route_metric(installed) >= INFINITY)
+        goto install;
+
+    if(route_metric(installed) >= route_metric(route) &&
+       route_smoothed_metric(installed) > route_smoothed_metric(route))
+        goto install;
+
+    return;
+
+ install:
+    switch_routes(installed, route);
+    if(installed && route->installed)
+        send_triggered_update(route, installed->src, route_metric(installed));
+    else
+        send_update(NULL, 1, route->src->prefix, route->src->plen);
+    return;
+}
+
+void
+retract_neighbour_routes(struct neighbour *neigh)
+{
+    int i;
+
+    for(i = 0; i < route_slots; i++) {
+        struct babel_route *r = routes[i];
+        while(r) {
+            if(r->neigh == neigh) {
+                if(r->refmetric != INFINITY) {
+                    unsigned short oldmetric = route_metric(r);
+                    retract_route(r);
+                    if(oldmetric != INFINITY)
+                        route_changed(r, r->src, oldmetric);
+                }
+            }
+            r = r->next;
+        }
+    }
+}
+
+void
+send_triggered_update(struct babel_route *route, struct source *oldsrc,
+                      unsigned oldmetric)
+{
+    unsigned newmetric, diff;
+    /* 1 means send speedily, 2 means resend */
+    int urgent;
+
+    if(!route->installed)
+        return;
+
+    newmetric = route_metric(route);
+    diff =
+        newmetric >= oldmetric ? newmetric - oldmetric : oldmetric - newmetric;
+
+    if(route->src != oldsrc || (oldmetric < INFINITY && newmetric >= INFINITY))
+        /* Switching sources can cause transient routing loops.
+           Retractions can cause blackholes. */
+        urgent = 2;
+    else if(newmetric > oldmetric && oldmetric < 6 * 256 && diff >= 512)
+        /* Route getting significantly worse */
+        urgent = 1;
+    else if(unsatisfied_request(route->src->prefix, route->src->plen,
+                                route->seqno, route->src->id))
+        /* Make sure that requests are satisfied speedily */
+        urgent = 1;
+    else if(oldmetric >= INFINITY && newmetric < INFINITY)
+        /* New route */
+        urgent = 0;
+    else if(newmetric < oldmetric && diff < 1024)
+        /* Route getting better.  This may be a transient fluctuation, so
+           don't advertise it to avoid making routes unfeasible later on. */
+        return;
+    else if(diff < 384)
+        /* Don't fret about trivialities */
+        return;
+    else
+        urgent = 0;
+
+    if(urgent >= 2)
+        send_update_resend(NULL, route->src->prefix, route->src->plen);
+    else
+        send_update(NULL, urgent, route->src->prefix, route->src->plen);
+
+    if(oldmetric < INFINITY) {
+        if(newmetric >= oldmetric + 512) {
+            send_request_resend(NULL, route->src->prefix, route->src->plen,
+                                route->src->metric >= INFINITY ?
+                                route->src->seqno :
+                                seqno_plus(route->src->seqno, 1),
+                                route->src->id);
+        } else if(newmetric >= oldmetric + 288) {
+            send_request(NULL, route->src->prefix, route->src->plen);
+        }
+    }
+}
+
+/* A route has just changed.  Decide whether to switch to a different route or
+   send an update. */
+void
+route_changed(struct babel_route *route,
+              struct source *oldsrc, unsigned short oldmetric)
+{
+    if(route->installed) {
+        struct babel_route *better_route;
+        /* Do this unconditionally -- microoptimisation is not worth it. */
+        better_route =
+            find_best_route(route->src->prefix, route->src->plen, 1, NULL);
+        if(better_route && route_metric(better_route) < route_metric(route))
+            consider_route(better_route);
+    }
+
+    if(route->installed) {
+        /* We didn't change routes after all. */
+        send_triggered_update(route, oldsrc, oldmetric);
+    } else {
+        /* Reconsider routes even when their metric didn't decrease,
+           they may not have been feasible before. */
+        consider_route(route);
+    }
+}
+
+/* We just lost the installed route to a given destination. */
+void
+route_lost(struct source *src, unsigned oldmetric)
+{
+    struct babel_route *new_route;
+    new_route = find_best_route(src->prefix, src->plen, 1, NULL);
+    if(new_route) {
+        consider_route(new_route);
+    } else if(oldmetric < INFINITY) {
+        /* Avoid creating a blackhole. */
+        send_update_resend(NULL, src->prefix, src->plen);
+        /* If the route was usable enough, try to get an alternate one.
+           If it was not, we could be dealing with oscillations around
+           the value of INFINITY. */
+        if(oldmetric <= INFINITY / 2)
+            send_request_resend(NULL, src->prefix, src->plen,
+                                src->metric >= INFINITY ?
+                                src->seqno : seqno_plus(src->seqno, 1),
+                                src->id);
+    }
+}
+
+/* This is called periodically to flush old routes.  It will also send
+   requests for routes that are about to expire. */
+void
+expire_routes(void)
+{
+    struct babel_route *r;
+    int i;
+
+    debugf(BABEL_DEBUG_COMMON,"Expiring old routes.");
+
+    i = 0;
+    while(i < route_slots) {
+        r = routes[i];
+        while(r) {
+            /* Protect against clock being stepped. */
+            if(r->time > babel_now.tv_sec || route_old(r)) {
+                flush_route(r);
+                goto again;
+            }
+
+            update_route_metric(r);
+
+            if(r->installed && r->refmetric < INFINITY) {
+                if(route_old(r))
+                    /* Route about to expire, send a request. */
+                    send_unicast_request(r->neigh,
+                                         r->src->prefix, r->src->plen);
+            }
+            r = r->next;
+        }
+        i++;
+    again:
+        ;
+    }
+}