Adding upstream version 2.2.0.upstream/2.2.0upstream

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

1 files changed, 236 insertions, 0 deletions

diff --git a/src/lib/dhcp/protocol_util.cc b/src/lib/dhcp/protocol_util.cc
new file mode 100644
index 0000000..da42511
--- /dev/null
+++ b/src/lib/dhcp/protocol_util.cc
@@ -0,0 +1,236 @@
+// Copyright (C) 2013-2019 Internet Systems Consortium, Inc. ("ISC")
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#include <config.h>
+#include <asiolink/io_address.h>
+#include <dhcp/dhcp6.h>
+#include <dhcp/protocol_util.h>
+#include <boost/static_assert.hpp>
+// in_systm.h is required on some some BSD systems
+// complaining that n_time is undefined but used
+// in ip.h.
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+
+using namespace isc::asiolink;
+using namespace isc::util;
+
+namespace isc {
+namespace dhcp {
+
+void
+decodeEthernetHeader(InputBuffer& buf, Pkt4Ptr& pkt) {
+    // The size of the buffer to be parsed must not be lower
+    // then the size of the Ethernet frame header.
+    if (buf.getLength() - buf.getPosition() < ETHERNET_HEADER_LEN) {
+        isc_throw(InvalidPacketHeader, "size of ethernet header in received "
+                  << "packet is invalid, expected at least "
+                  << ETHERNET_HEADER_LEN << " bytes, received "
+                  << buf.getLength() - buf.getPosition() << " bytes");
+    }
+    // Packet object must not be NULL. We want to output some values
+    // to this object.
+    if (!pkt) {
+        isc_throw(BadValue, "NULL packet object provided when parsing ethernet"
+                  " frame header");
+    }
+
+    // The size of the single address is always lower then the size of
+    // the header that holds this address. Otherwise, it is a programming
+    // error that we want to detect in the compilation time.
+    BOOST_STATIC_ASSERT(ETHERNET_HEADER_LEN > HWAddr::ETHERNET_HWADDR_LEN);
+
+    // Remember initial position.
+    size_t start_pos = buf.getPosition();
+
+    // Read the destination HW address.
+    std::vector<uint8_t> dest_addr;
+    buf.readVector(dest_addr, HWAddr::ETHERNET_HWADDR_LEN);
+    pkt->setLocalHWAddr(HWTYPE_ETHERNET, HWAddr::ETHERNET_HWADDR_LEN, dest_addr);
+    // Read the source HW address.
+    std::vector<uint8_t> src_addr;
+    buf.readVector(src_addr, HWAddr::ETHERNET_HWADDR_LEN);
+    pkt->setRemoteHWAddr(HWTYPE_ETHERNET, HWAddr::ETHERNET_HWADDR_LEN, src_addr);
+    // Move the buffer read pointer to the end of the Ethernet frame header.
+    buf.setPosition(start_pos + ETHERNET_HEADER_LEN);
+}
+
+void
+decodeIpUdpHeader(InputBuffer& buf, Pkt4Ptr& pkt) {
+    // The size of the buffer must be at least equal to the minimal size of
+    // the IPv4 packet header plus UDP header length.
+    if (buf.getLength() - buf.getPosition() < MIN_IP_HEADER_LEN + UDP_HEADER_LEN) {
+        isc_throw(InvalidPacketHeader, "the total size of the IP and UDP headers in "
+                  << "received packet is invalid, expected at least "
+                  << MIN_IP_HEADER_LEN + UDP_HEADER_LEN
+                  << " bytes, received " << buf.getLength() - buf.getPosition()
+                  << " bytes");
+    }
+
+    // Packet object must not be NULL.
+    if (!pkt) {
+        isc_throw(BadValue, "NULL packet object provided when parsing IP and UDP"
+                  " packet headers");
+    }
+
+    BOOST_STATIC_ASSERT(IP_SRC_ADDR_OFFSET < MIN_IP_HEADER_LEN);
+
+    // Remember initial position of the read pointer.
+    size_t start_pos = buf.getPosition();
+
+    // Read IP header length (mask most significant bits as they indicate IP version).
+    uint8_t ip_len = buf.readUint8() & 0xF;
+    // IP length is the number of 4 byte chunks that construct IPv4 header.
+    // It must not be lower than 5 because first 20 bytes are fixed.
+    if (ip_len < 5) {
+        isc_throw(InvalidPacketHeader, "Value of the length of the IP header must not be"
+                  << " lower than 5 words. The length of the received header is "
+                  << static_cast<unsigned>(ip_len) << ".");
+    }
+
+    // Seek to the position of source IP address.
+    buf.setPosition(start_pos + IP_SRC_ADDR_OFFSET);
+    // Read source address.
+    pkt->setRemoteAddr(IOAddress(buf.readUint32()));
+    // Read destination address.
+    pkt->setLocalAddr(IOAddress(buf.readUint32()));
+
+    // Skip IP header options (if any) to start of the
+    // UDP header.
+    buf.setPosition(start_pos + ip_len * 4);
+
+    // Read source port from UDP header.
+    pkt->setRemotePort(buf.readUint16());
+    // Read destination port from UDP header.
+    pkt->setLocalPort(buf.readUint16());
+
+    // Set the pointer position to the first byte o the
+    // UDP payload (DHCP packet).
+    buf.setPosition(start_pos + ip_len * 4 + UDP_HEADER_LEN);
+}
+
+void
+writeEthernetHeader(const Pkt4Ptr& pkt, OutputBuffer& out_buf) {
+    // Set destination HW address.
+    HWAddrPtr remote_addr = pkt->getRemoteHWAddr();
+    if (remote_addr) {
+        if (remote_addr->hwaddr_.size() == HWAddr::ETHERNET_HWADDR_LEN) {
+            out_buf.writeData(&remote_addr->hwaddr_[0],
+                              HWAddr::ETHERNET_HWADDR_LEN);
+        } else {
+            isc_throw(BadValue, "invalid size of the remote HW address "
+                      << remote_addr->hwaddr_.size() << " when constructing"
+                      << " an ethernet frame header; expected size is"
+                      << " " << HWAddr::ETHERNET_HWADDR_LEN);
+        }
+    } else {
+        // HW address has not been specified. This is possible when receiving
+        // packet through a logical interface (e.g. lo). In such cases, we
+        // don't want to fail but rather provide a default HW address, which
+        // consists of zeros.
+        out_buf.writeData(&std::vector<uint8_t>(HWAddr::ETHERNET_HWADDR_LEN)[0],
+                          HWAddr::ETHERNET_HWADDR_LEN);
+    }
+
+    // Set source HW address.
+    HWAddrPtr local_addr = pkt->getLocalHWAddr();
+    if (local_addr) {
+        if (local_addr->hwaddr_.size() == HWAddr::ETHERNET_HWADDR_LEN) {
+            out_buf.writeData(&local_addr->hwaddr_[0],
+                              HWAddr::ETHERNET_HWADDR_LEN);
+        } else {
+            isc_throw(BadValue, "invalid size of the local HW address "
+                      << local_addr->hwaddr_.size() << " when constructing"
+                      << " an ethernet frame header; expected size is"
+                      << " " << HWAddr::ETHERNET_HWADDR_LEN);
+        }
+    } else {
+        // Provide default HW address.
+        out_buf.writeData(&std::vector<uint8_t>(HWAddr::ETHERNET_HWADDR_LEN)[0],
+                          HWAddr::ETHERNET_HWADDR_LEN);
+    }
+
+    // Type IP.
+    out_buf.writeUint16(ETHERNET_TYPE_IP);
+}
+
+void
+writeIpUdpHeader(const Pkt4Ptr& pkt, util::OutputBuffer& out_buf) {
+
+    out_buf.writeUint8(0x45); // IP version 4, IP header length 5
+    out_buf.writeUint8(IPTOS_LOWDELAY); // DSCP and ECN
+    out_buf.writeUint16(28 + pkt->getBuffer().getLength()); // Total length.
+    out_buf.writeUint16(0); // Identification
+    out_buf.writeUint16(0x4000); // Disable fragmentation.
+    out_buf.writeUint8(128); // TTL
+    out_buf.writeUint8(IPPROTO_UDP); // Protocol UDP.
+    out_buf.writeUint16(0); // Temporarily set checksum to 0.
+    out_buf.writeUint32(pkt->getLocalAddr().toUint32()); // Source address.
+    out_buf.writeUint32(pkt->getRemoteAddr().toUint32()); // Destination address.
+
+    // Calculate pseudo header checksum. It will be necessary to compute
+    // UDP checksum.
+    // Get the UDP length. This includes udp header's and data length.
+    uint32_t udp_len = 8 + pkt->getBuffer().getLength();
+    // The magic number "8" indicates the offset where the source address
+    // is stored in the buffer. This offset is counted here from the
+    // current tail of the buffer. Starting from this offset we calculate
+    // the checksum using 8 following bytes of data. This will include
+    // 4 bytes of source address and 4 bytes of destination address.
+    // The IPPROTO_UDP and udp_len are also added up to the checksum.
+    uint16_t pseudo_hdr_checksum =
+        calcChecksum(static_cast<const uint8_t*>(out_buf.getData()) + out_buf.getLength() - 8,
+                     8, IPPROTO_UDP + udp_len);
+
+    // Calculate IP header checksum.
+    uint16_t ip_checksum = ~calcChecksum(static_cast<const uint8_t*>(out_buf.getData())
+                                         + out_buf.getLength() - 20, 20);
+    // Write checksum in the IP header. The offset of the checksum is 10 bytes
+    // back from the tail of the current buffer.
+    out_buf.writeUint16At(ip_checksum, out_buf.getLength() - 10);
+
+    // Start UDP header.
+    out_buf.writeUint16(pkt->getLocalPort()); // Source port.
+    out_buf.writeUint16(pkt->getRemotePort()); // Destination port.
+    out_buf.writeUint16(udp_len); // Length of the header and data.
+
+    // Checksum is calculated from the contents of UDP header, data and pseudo ip header.
+    // The magic number "6" indicates that the UDP header starts at offset 6 from the
+    // tail of the current buffer. These 6 bytes contain source and destination port
+    // as well as the length of the header.
+    uint16_t udp_checksum =
+        ~calcChecksum(static_cast<const uint8_t*>(out_buf.getData()) + out_buf.getLength() - 6, 6,
+                      calcChecksum(static_cast<const uint8_t*>(pkt->getBuffer().getData()),
+                                   pkt->getBuffer().getLength(),
+                                   pseudo_hdr_checksum));
+    // Write UDP checksum.
+    out_buf.writeUint16(udp_checksum);
+}
+
+uint16_t
+calcChecksum(const uint8_t* buf, const uint32_t buf_size, uint32_t sum) {
+    uint32_t i;
+    for (i = 0; i < (buf_size & ~1U); i += 2) {
+        uint16_t chunk = buf[i] << 8 | buf[i + 1];
+        sum += chunk;
+        if (sum > 0xFFFF) {
+            sum -= 0xFFFF;
+        }
+    }
+    // If one byte has left, we also need to add it to the checksum.
+    if (i < buf_size) {
+        sum += buf[i] << 8;
+        if (sum > 0xFFFF) {
+            sum -= 0xFFFF;
+        }
+    }
+
+    return (sum);
+
+}
+
+}
+}