Added SNAP. Couldn't test it yet.

src/snap.cpp

@@ -0,0 +1,59 @@
+/*
+ * libtins is a net packet wrapper library for crafting and
+ * interpreting sniffed packets.
+ *
+ * Copyright (C) 2011 Nasel
+ *
+ * This library 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.
+ *
+ * This library 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 this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <cstring>
+#include <cassert>
+#ifndef WIN32
+    #include <net/ethernet.h>
+#endif
+#include "snap.h"
+#include "utils.h"
+
+
+Tins::SNAP::SNAP(PDU *child) : PDU(0xff, child) {
+    std::memset(&_snap, 0, sizeof(_snap));
+    _snap.dsap = _snap.ssap = 0xaa;
+    _snap.id = 3;
+}
+
+uint32_t Tins::SNAP::header_size() const {
+    return sizeof(_snap);
+}
+
+void Tins::SNAP::write_serialization(uint8_t *buffer, uint32_t total_sz, const PDU *parent) {
+    assert(total_sz >= sizeof(_snap));
+    if (!_snap.eth_type && inner_pdu()) {
+        uint16_t type = ETHERTYPE_IP;
+        switch (inner_pdu()->pdu_type()) {
+            case PDU::IP:
+                type = ETHERTYPE_IP;
+                break;
+            case PDU::ARP:
+                type = ETHERTYPE_ARP;
+                break;
+            default:
+                type = 0;
+        }
+        _snap.eth_type = Utils::net_to_host_s(type);
+    }
+    std::memcpy(buffer, &_snap, sizeof(_snap));
+}
+