babeld: Initial import, for Babel routing protocol.

* Initial import of the Babel routing protocol, ported to Quagga.
* LICENCE: Update the original LICENCE file to include all known potentially
  applicable copyright claims.  Ask that any future contributors to babeld/
  grant MIT/X11 licence to their work.
* *.{c,h}: Add GPL headers, in according with the SFLC guidance on
  dealing with potentially mixed GPL/other licensed work, at:

  https://www.softwarefreedom.org/resources/2007/gpl-non-gpl-collaboration.html
diff --git a/babeld/net.c b/babeld/net.c
new file mode 100644
index 0000000..5cb1236
--- /dev/null
+++ b/babeld/net.c
@@ -0,0 +1,229 @@
+/*  
+ *  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 <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <errno.h>
+
+#include "babeld.h"
+#include "util.h"
+#include "net.h"
+
+int
+babel_socket(int port)
+{
+    struct sockaddr_in6 sin6;
+    int s, rc;
+    int saved_errno;
+    int one = 1, zero = 0;
+
+    s = socket(PF_INET6, SOCK_DGRAM, 0);
+    if(s < 0)
+        return -1;
+
+    rc = setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
+    if(rc < 0)
+        goto fail;
+
+    rc = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+    if(rc < 0)
+        goto fail;
+
+    rc = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP,
+                    &zero, sizeof(zero));
+    if(rc < 0)
+        goto fail;
+
+    rc = setsockopt(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS,
+                    &one, sizeof(one));
+    if(rc < 0)
+        goto fail;
+
+    rc = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS,
+                    &one, sizeof(one));
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_GETFL, 0);
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_SETFL, (rc | O_NONBLOCK));
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_GETFD, 0);
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_SETFD, rc | FD_CLOEXEC);
+    if(rc < 0)
+        goto fail;
+
+    memset(&sin6, 0, sizeof(sin6));
+    sin6.sin6_family = AF_INET6;
+    sin6.sin6_port = htons(port);
+    rc = bind(s, (struct sockaddr*)&sin6, sizeof(sin6));
+    if(rc < 0)
+        goto fail;
+
+    return s;
+
+ fail:
+    saved_errno = errno;
+    close(s);
+    errno = saved_errno;
+    return -1;
+}
+
+int
+babel_recv(int s, void *buf, int buflen, struct sockaddr *sin, int slen)
+{
+    struct iovec iovec;
+    struct msghdr msg;
+    int rc;
+
+    memset(&msg, 0, sizeof(msg));
+    iovec.iov_base = buf;
+    iovec.iov_len = buflen;
+    msg.msg_name = sin;
+    msg.msg_namelen = slen;
+    msg.msg_iov = &iovec;
+    msg.msg_iovlen = 1;
+
+    rc = recvmsg(s, &msg, 0);
+    return rc;
+}
+
+int
+babel_send(int s,
+           const void *buf1, int buflen1, const void *buf2, int buflen2,
+           const struct sockaddr *sin, int slen)
+{
+    struct iovec iovec[2];
+    struct msghdr msg;
+    int rc;
+
+    iovec[0].iov_base = (void*)buf1;
+    iovec[0].iov_len = buflen1;
+    iovec[1].iov_base = (void*)buf2;
+    iovec[1].iov_len = buflen2;
+    memset(&msg, 0, sizeof(msg));
+    msg.msg_name = (struct sockaddr*)sin;
+    msg.msg_namelen = slen;
+    msg.msg_iov = iovec;
+    msg.msg_iovlen = 2;
+
+ again:
+    rc = sendmsg(s, &msg, 0);
+    if(rc < 0) {
+        if(errno == EINTR)
+            goto again;
+        else if(errno == EAGAIN) {
+            int rc2;
+            rc2 = wait_for_fd(1, s, 5);
+            if(rc2 > 0)
+                goto again;
+            errno = EAGAIN;
+        }
+    }
+    return rc;
+}
+
+int
+tcp_server_socket(int port, int local)
+{
+    struct sockaddr_in6 sin6;
+    int s, rc, saved_errno;
+    int one = 1;
+
+    s = socket(PF_INET6, SOCK_STREAM, 0);
+    if(s < 0)
+        return -1;
+
+    rc = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_GETFL, 0);
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_SETFL, (rc | O_NONBLOCK));
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_GETFD, 0);
+    if(rc < 0)
+        goto fail;
+
+    rc = fcntl(s, F_SETFD, rc | FD_CLOEXEC);
+    if(rc < 0)
+        goto fail;
+
+    memset(&sin6, 0, sizeof(sin6));
+    sin6.sin6_family = AF_INET6;
+    sin6.sin6_port = htons(port);
+    if(local) {
+        rc = inet_pton(AF_INET6, "::1", &sin6.sin6_addr);
+        if(rc < 0)
+            goto fail;
+    }
+    rc = bind(s, (struct sockaddr*)&sin6, sizeof(sin6));
+    if(rc < 0)
+        goto fail;
+
+    rc = listen(s, 2);
+    if(rc < 0)
+        goto fail;
+
+    return s;
+
+ fail:
+    saved_errno = errno;
+    close(s);
+    errno = saved_errno;
+    return -1;
+}