diff --git a/babeld/source.c b/babeld/source.c
new file mode 100644
index 0000000..cc4ed44
--- /dev/null
+++ b/babeld/source.c
@@ -0,0 +1,159 @@
+/*  
+ *  This file is free software: you may copy, redistribute and/or modify it  
+ *  under the terms of the GNU General Public License as published by the  
+ *  Free Software Foundation, either version 2 of the License, or (at your  
+ *  option) any later version.  
+ *  
+ *  This file is distributed in the hope that it will be useful, but  
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of  
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  
+ *  General Public License for more details.  
+ *  
+ *  You should have received a copy of the GNU General Public License  
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.  
+ *  
+ * This file incorporates work covered by the following copyright and  
+ * permission notice:  
+ *  
+Copyright (c) 2007, 2008 by 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 <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/time.h>
+
+#include "babel_main.h"
+#include "babeld.h"
+#include "util.h"
+#include "source.h"
+#include "babel_interface.h"
+#include "route.h"
+
+struct source *srcs = NULL;
+
+struct source*
+find_source(const unsigned char *id, const unsigned char *p, unsigned char plen,
+            int create, unsigned short seqno)
+{
+    struct source *src;
+
+    for(src = srcs; src; src = src->next) {
+        /* This should really be a hash table.  For now, check the
+           last byte first. */
+        if(src->id[7] != id[7])
+            continue;
+        if(memcmp(src->id, id, 8) != 0)
+            continue;
+        if(source_match(src, p, plen))
+           return src;
+    }
+
+    if(!create)
+        return NULL;
+
+    src = malloc(sizeof(struct source));
+    if(src == NULL) {
+        zlog_err("malloc(source): %s", safe_strerror(errno));
+        return NULL;
+    }
+
+    memcpy(src->id, id, 8);
+    memcpy(src->prefix, p, 16);
+    src->plen = plen;
+    src->seqno = seqno;
+    src->metric = INFINITY;
+    src->time = babel_now.tv_sec;
+    src->next = srcs;
+    srcs = src;
+    return src;
+}
+
+int
+flush_source(struct source *src)
+{
+    /* This is absolutely horrible -- it makes expire_sources quadratic.
+       But it's not called very often. */
+
+    if (babel_route_get_by_source(src) != NULL)
+        return 0;
+
+    if(srcs == src) {
+        srcs = src->next;
+    } else {
+        struct source *previous = srcs;
+        while(previous->next != src)
+            previous = previous->next;
+        previous->next = src->next;
+    }
+
+    free(src);
+    return 1;
+}
+
+int
+source_match(struct source *src,
+             const unsigned char *p, unsigned char plen)
+{
+    if(src->plen != plen)
+        return 0;
+    if(src->prefix[15] != p[15])
+        return 0;
+    if(memcmp(src->prefix, p, 16) != 0)
+        return 0;
+    return 1;
+}
+
+void
+update_source(struct source *src,
+              unsigned short seqno, unsigned short metric)
+{
+    if(metric >= INFINITY)
+        return;
+
+    if(src->time < babel_now.tv_sec - SOURCE_GC_TIME ||
+       seqno_compare(src->seqno, seqno) < 0 ||
+       (src->seqno == seqno && src->metric > metric)) {
+        src->seqno = seqno;
+        src->metric = metric;
+    }
+    src->time = babel_now.tv_sec;
+}
+
+void
+expire_sources()
+{
+    struct source *src;
+
+    src = srcs;
+    while(src) {
+        if(src->time > babel_now.tv_sec)
+            /* clock stepped */
+            src->time = babel_now.tv_sec;
+        if(src->time < babel_now.tv_sec - SOURCE_GC_TIME) {
+            struct source *old = src;
+            src = src->next;
+            flush_source(old);
+            continue;
+        }
+        src = src->next;
+    }
+}