sd-network: IPv4 link-local support [v2]

Implements IPv4LL with respect to RFC 3927
(http://tools.ietf.org/rfc/rfc3927.txt) and integrates it
with networkd. Majority of the IPv4LL state machine is
taken from avahi (http://avahi.org/) project's autoip.

IPv4LL can be enabled by IPv4LL=yes under [Network]
section of .network file.

IPv4LL works independent of DHCP but if DHCP lease is
aquired, then LL address will be dropped.

[tomegun: removed a trailing newline and a compiler warning]

1 files changed, 71 insertions, 0 deletions

diff --git a/src/libsystemd-network/ipv4ll-packet.c b/src/libsystemd-network/ipv4ll-packet.c
new file mode 100644
index 000000000..2b6c73ab4
--- /dev/null
+++ b/src/libsystemd-network/ipv4ll-packet.c
@@ -0,0 +1,71 @@
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 Axis Communications AB. All rights reserved.
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+#include <arpa/inet.h>
+
+#include "util.h"
+#include "ipv4ll-internal.h"
+
+void arp_packet_init(struct ether_arp *arp) {
+        assert(arp);
+
+        memzero(arp, sizeof(struct ether_arp));
+        /* Header */
+        arp->ea_hdr.ar_hrd = htons(ARPHRD_ETHER); /* HTYPE */
+        arp->ea_hdr.ar_pro = htons(ETHERTYPE_IP); /* PTYPE */
+        arp->ea_hdr.ar_hln = ETH_ALEN; /* HLEN */
+        arp->ea_hdr.ar_pln = sizeof arp->arp_spa; /* PLEN */
+        arp->ea_hdr.ar_op = htons(ARPOP_REQUEST); /* REQUEST */
+}
+
+void arp_packet_probe(struct ether_arp *arp, be32_t pa, const struct ether_addr *ha) {
+        assert(ha);
+
+        arp_packet_init(arp);
+        memcpy(arp->arp_sha, ha, ETH_ALEN);
+        memcpy(arp->arp_tpa, &pa, sizeof(pa));
+}
+
+void arp_packet_announcement(struct ether_arp *arp, be32_t pa, const struct ether_addr *ha) {
+        assert(ha);
+
+        arp_packet_init(arp);
+        memcpy(arp->arp_sha, ha, ETH_ALEN);
+        memcpy(arp->arp_tpa, &pa, sizeof(pa));
+        memcpy(arp->arp_spa, &pa, sizeof(pa));
+}
+
+int arp_packet_verify_headers(struct ether_arp *arp) {
+        assert(arp);
+
+        if (arp->ea_hdr.ar_hrd != htons(ARPHRD_ETHER)) {
+                log_ipv4ll(NULL, "ignoring packet: header is not ARPHRD_ETHER");
+                return -EINVAL;
+        }
+        if (arp->ea_hdr.ar_pro != htons(ETHERTYPE_IP)) {
+                log_ipv4ll(NULL, "ignoring packet: protocol is not ETHERTYPE_IP");
+                return -EINVAL;
+        }
+        if (arp->ea_hdr.ar_op != htons(ARPOP_REQUEST) &&
+            arp->ea_hdr.ar_op != htons(ARPOP_REPLY)) {
+                log_ipv4ll(NULL, "ignoring packet: operation is not ARPOP_REQUEST or ARPOP_REPLY");
+                return -EINVAL;
+        }
+
+        return 0;
+}