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ZeroTierOne/vsprojects/TapDriver/dhcp.c

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/*
* TAP-Windows -- A kernel driver to provide virtual tap
* device functionality on Windows.
*
* This code was inspired by the CIPE-Win32 driver by Damion K. Wilson.
*
* This source code is Copyright (C) 2002-2010 OpenVPN Technologies, Inc.,
* and is released under the GPL version 2 (see below).
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program 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 (see the file COPYING included with this
* distribution); if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
//=========================
// Code to set DHCP options
//=========================
VOID
SetDHCPOpt (DHCPMsg *m, void *data, unsigned int len)
{
if (!m->overflow)
{
if (m->optlen + len <= DHCP_OPTIONS_BUFFER_SIZE)
{
if (len)
{
NdisMoveMemory (m->msg.options + m->optlen, data, len);
m->optlen += len;
}
}
else
{
m->overflow = TRUE;
}
}
}
VOID
SetDHCPOpt0 (DHCPMsg *msg, int type)
{
DHCPOPT0 opt;
opt.type = (UCHAR) type;
SetDHCPOpt (msg, &opt, sizeof (opt));
}
VOID
SetDHCPOpt8 (DHCPMsg *msg, int type, ULONG data)
{
DHCPOPT8 opt;
opt.type = (UCHAR) type;
opt.len = sizeof (opt.data);
opt.data = (UCHAR) data;
SetDHCPOpt (msg, &opt, sizeof (opt));
}
VOID
SetDHCPOpt32 (DHCPMsg *msg, int type, ULONG data)
{
DHCPOPT32 opt;
opt.type = (UCHAR) type;
opt.len = sizeof (opt.data);
opt.data = data;
SetDHCPOpt (msg, &opt, sizeof (opt));
}
//==============
// Checksum code
//==============
USHORT
ip_checksum (const UCHAR *buf, const int len_ip_header)
{
USHORT word16;
ULONG sum = 0;
int i;
// make 16 bit words out of every two adjacent 8 bit words in the packet
// and add them up
for (i = 0; i < len_ip_header - 1; i += 2) {
word16 = ((buf[i] << 8) & 0xFF00) + (buf[i+1] & 0xFF);
sum += (ULONG) word16;
}
// take only 16 bits out of the 32 bit sum and add up the carries
while (sum >> 16)
sum = (sum & 0xFFFF) + (sum >> 16);
// one's complement the result
return ((USHORT) ~sum);
}
USHORT
udp_checksum (const UCHAR *buf,
const int len_udp,
const UCHAR *src_addr,
const UCHAR *dest_addr)
{
USHORT word16;
ULONG sum = 0;
int i;
// make 16 bit words out of every two adjacent 8 bit words and
// calculate the sum of all 16 bit words
for (i = 0; i < len_udp; i += 2){
word16 = ((buf[i] << 8) & 0xFF00) + ((i + 1 < len_udp) ? (buf[i+1] & 0xFF) : 0);
sum += word16;
}
// add the UDP pseudo header which contains the IP source and destination addresses
for (i = 0; i < 4; i += 2){
word16 =((src_addr[i] << 8) & 0xFF00) + (src_addr[i+1] & 0xFF);
sum += word16;
}
for (i = 0; i < 4; i += 2){
word16 =((dest_addr[i] << 8) & 0xFF00) + (dest_addr[i+1] & 0xFF);
sum += word16;
}
// the protocol number and the length of the UDP packet
sum += (USHORT) IPPROTO_UDP + (USHORT) len_udp;
// keep only the last 16 bits of the 32 bit calculated sum and add the carries
while (sum >> 16)
sum = (sum & 0xFFFF) + (sum >> 16);
// Take the one's complement of sum
return ((USHORT) ~sum);
}
//================================
// Set IP and UDP packet checksums
//================================
VOID
SetChecksumDHCPMsg (DHCPMsg *m)
{
// Set IP checksum
m->msg.pre.ip.check = htons (ip_checksum ((UCHAR *) &m->msg.pre.ip, sizeof (IPHDR)));
// Set UDP Checksum
m->msg.pre.udp.check = htons (udp_checksum ((UCHAR *) &m->msg.pre.udp,
sizeof (UDPHDR) + sizeof (DHCP) + m->optlen,
(UCHAR *)&m->msg.pre.ip.saddr,
(UCHAR *)&m->msg.pre.ip.daddr));
}
//===================
// DHCP message tests
//===================
int
GetDHCPMessageType (const DHCP *dhcp, const int optlen)
{
const UCHAR *p = (UCHAR *) (dhcp + 1);
int i;
for (i = 0; i < optlen; ++i)
{
const UCHAR type = p[i];
const int room = optlen - i - 1;
if (type == DHCP_END) // didn't find what we were looking for
return -1;
else if (type == DHCP_PAD) // no-operation
;
else if (type == DHCP_MSG_TYPE) // what we are looking for
{
if (room >= 2)
{
if (p[i+1] == 1) // message length should be 1
return p[i+2]; // return message type
}
return -1;
}
else // some other message
{
if (room >= 1)
{
const int len = p[i+1]; // get message length
i += (len + 1); // advance to next message
}
}
}
return -1;
}
BOOLEAN
DHCPMessageOurs (const TapAdapterPointer p_Adapter,
const ETH_HEADER *eth,
const IPHDR *ip,
const UDPHDR *udp,
const DHCP *dhcp)
{
// Must be UDPv4 protocol
if (!(eth->proto == htons (ETH_P_IP) && ip->protocol == IPPROTO_UDP))
return FALSE;
// Source MAC must be our adapter
if (!MAC_EQUAL (eth->src, p_Adapter->m_MAC))
return FALSE;
// Dest MAC must be either broadcast or our virtual DHCP server
if (!(MAC_EQUAL (eth->dest, p_Adapter->m_MAC_Broadcast)
|| MAC_EQUAL (eth->dest, p_Adapter->m_dhcp_server_mac)))
return FALSE;
// Port numbers must be correct
if (!(udp->dest == htons (BOOTPS_PORT)
&& udp->source == htons (BOOTPC_PORT)))
return FALSE;
// Hardware address must be MAC addr sized
if (!(dhcp->hlen == sizeof (MACADDR)))
return FALSE;
// Hardware address must match our adapter
if (!MAC_EQUAL (eth->src, dhcp->chaddr))
return FALSE;
return TRUE;
}
//=====================================================
// Build all of DHCP packet except for DHCP options.
// Assume that *p has been zeroed before we are called.
//=====================================================
VOID
BuildDHCPPre (const TapAdapterPointer a,
DHCPPre *p,
const ETH_HEADER *eth,
const IPHDR *ip,
const UDPHDR *udp,
const DHCP *dhcp,
const int optlen,
const int type)
{
// Should we broadcast or direct to a specific MAC / IP address?
const BOOLEAN broadcast = (type == DHCPNAK
|| MAC_EQUAL (eth->dest, a->m_MAC_Broadcast));
// Build ethernet header
COPY_MAC (p->eth.src, a->m_dhcp_server_mac);
if (broadcast)
COPY_MAC (p->eth.dest, a->m_MAC_Broadcast);
else
COPY_MAC (p->eth.dest, eth->src);
p->eth.proto = htons (ETH_P_IP);
// Build IP header
p->ip.version_len = (4 << 4) | (sizeof (IPHDR) >> 2);
p->ip.tos = 0;
p->ip.tot_len = htons (sizeof (IPHDR) + sizeof (UDPHDR) + sizeof (DHCP) + optlen);
p->ip.id = 0;
p->ip.frag_off = 0;
p->ip.ttl = 16;
p->ip.protocol = IPPROTO_UDP;
p->ip.check = 0;
p->ip.saddr = a->m_dhcp_server_ip;
if (broadcast)
p->ip.daddr = ~0;
else
p->ip.daddr = a->m_dhcp_addr;
// Build UDP header
p->udp.source = htons (BOOTPS_PORT);
p->udp.dest = htons (BOOTPC_PORT);
p->udp.len = htons (sizeof (UDPHDR) + sizeof (DHCP) + optlen);
p->udp.check = 0;
// Build DHCP response
p->dhcp.op = BOOTREPLY;
p->dhcp.htype = 1;
p->dhcp.hlen = sizeof (MACADDR);
p->dhcp.hops = 0;
p->dhcp.xid = dhcp->xid;
p->dhcp.secs = 0;
p->dhcp.flags = 0;
p->dhcp.ciaddr = 0;
if (type == DHCPNAK)
p->dhcp.yiaddr = 0;
else
p->dhcp.yiaddr = a->m_dhcp_addr;
p->dhcp.siaddr = a->m_dhcp_server_ip;
p->dhcp.giaddr = 0;
COPY_MAC (p->dhcp.chaddr, eth->src);
p->dhcp.magic = htonl (0x63825363);
}
//=============================
// Build specific DHCP messages
//=============================
VOID
SendDHCPMsg (const TapAdapterPointer a,
const int type,
const ETH_HEADER *eth,
const IPHDR *ip,
const UDPHDR *udp,
const DHCP *dhcp)
{
DHCPMsg *pkt;
if (!(type == DHCPOFFER || type == DHCPACK || type == DHCPNAK))
{
DEBUGP (("[TAP] SendDHCPMsg: Bad DHCP type: %d\n", type));
return;
}
pkt = (DHCPMsg *) MemAlloc (sizeof (DHCPMsg), TRUE);
if (pkt)
{
//-----------------------
// Build DHCP options
//-----------------------
// Message Type
SetDHCPOpt8 (pkt, DHCP_MSG_TYPE, type);
// Server ID
SetDHCPOpt32 (pkt, DHCP_SERVER_ID, a->m_dhcp_server_ip);
if (type == DHCPOFFER || type == DHCPACK)
{
// Lease Time
SetDHCPOpt32 (pkt, DHCP_LEASE_TIME, htonl (a->m_dhcp_lease_time));
// Netmask
SetDHCPOpt32 (pkt, DHCP_NETMASK, a->m_dhcp_netmask);
// Other user-defined options
SetDHCPOpt (pkt,
a->m_dhcp_user_supplied_options_buffer,
a->m_dhcp_user_supplied_options_buffer_len);
}
// End
SetDHCPOpt0 (pkt, DHCP_END);
if (!DHCPMSG_OVERFLOW (pkt))
{
// The initial part of the DHCP message (not including options) gets built here
BuildDHCPPre (a,
&pkt->msg.pre,
eth,
ip,
udp,
dhcp,
DHCPMSG_LEN_OPT (pkt),
type);
SetChecksumDHCPMsg (pkt);
DUMP_PACKET ("DHCPMsg",
DHCPMSG_BUF (pkt),
DHCPMSG_LEN_FULL (pkt));
// Return DHCP response to kernel
InjectPacketDeferred (a,
DHCPMSG_BUF (pkt),
DHCPMSG_LEN_FULL (pkt));
}
else
{
DEBUGP (("[TAP] SendDHCPMsg: DHCP buffer overflow\n"));
}
MemFree (pkt, sizeof (DHCPMsg));
}
}
//===================================================================
// Handle a BOOTPS packet produced by the local system to
// resolve the address/netmask of this adapter.
// If we are in TAP_WIN_IOCTL_CONFIG_DHCP_MASQ mode, reply
// to the message. Return TRUE if we processed the passed
// message, so that downstream stages can ignore it.
//===================================================================
BOOLEAN
ProcessDHCP (TapAdapterPointer p_Adapter,
const ETH_HEADER *eth,
const IPHDR *ip,
const UDPHDR *udp,
const DHCP *dhcp,
int optlen)
{
int msg_type;
// Sanity check IP header
if (!(ntohs (ip->tot_len) == sizeof (IPHDR) + sizeof (UDPHDR) + sizeof (DHCP) + optlen
&& (ntohs (ip->frag_off) & IP_OFFMASK) == 0))
return TRUE;
// Does this message belong to us?
if (!DHCPMessageOurs (p_Adapter, eth, ip, udp, dhcp))
return FALSE;
msg_type = GetDHCPMessageType (dhcp, optlen);
// Drop non-BOOTREQUEST messages
if (dhcp->op != BOOTREQUEST)
return TRUE;
// Drop any messages except DHCPDISCOVER or DHCPREQUEST
if (!(msg_type == DHCPDISCOVER || msg_type == DHCPREQUEST))
return TRUE;
// Should we reply with DHCPOFFER, DHCPACK, or DHCPNAK?
if (msg_type == DHCPREQUEST
&& ((dhcp->ciaddr && dhcp->ciaddr != p_Adapter->m_dhcp_addr)
|| !p_Adapter->m_dhcp_received_discover
|| p_Adapter->m_dhcp_bad_requests >= BAD_DHCPREQUEST_NAK_THRESHOLD))
SendDHCPMsg (p_Adapter,
DHCPNAK,
eth, ip, udp, dhcp);
else
SendDHCPMsg (p_Adapter,
(msg_type == DHCPDISCOVER ? DHCPOFFER : DHCPACK),
eth, ip, udp, dhcp);
// Remember if we received a DHCPDISCOVER
if (msg_type == DHCPDISCOVER)
p_Adapter->m_dhcp_received_discover = TRUE;
// Is this a bad DHCPREQUEST?
if (msg_type == DHCPREQUEST && dhcp->ciaddr && dhcp->ciaddr != p_Adapter->m_dhcp_addr)
++p_Adapter->m_dhcp_bad_requests;
return TRUE;
}
#if DBG
const char *
message_op_text (int op)
{
switch (op)
{
case BOOTREQUEST:
return "BOOTREQUEST";
case BOOTREPLY:
return "BOOTREPLY";
default:
return "???";
}
}
const char *
message_type_text (int type)
{
switch (type)
{
case DHCPDISCOVER:
return "DHCPDISCOVER";
case DHCPOFFER:
return "DHCPOFFER";
case DHCPREQUEST:
return "DHCPREQUEST";
case DHCPDECLINE:
return "DHCPDECLINE";
case DHCPACK:
return "DHCPACK";
case DHCPNAK:
return "DHCPNAK";
case DHCPRELEASE:
return "DHCPRELEASE";
case DHCPINFORM:
return "DHCPINFORM";
default:
return "???";
}
}
const char *
port_name (int port)
{
switch (port)
{
case BOOTPS_PORT:
return "BOOTPS";
case BOOTPC_PORT:
return "BOOTPC";
default:
return "unknown";
}
}
VOID
DumpDHCP (const ETH_HEADER *eth,
const IPHDR *ip,
const UDPHDR *udp,
const DHCP *dhcp,
const int optlen)
{
DEBUGP ((" %s", message_op_text (dhcp->op)));
DEBUGP ((" %s ", message_type_text (GetDHCPMessageType (dhcp, optlen))));
PrIP (ip->saddr);
DEBUGP ((":%s[", port_name (ntohs (udp->source))));
PrMac (eth->src);
DEBUGP (("] -> "));
PrIP (ip->daddr);
DEBUGP ((":%s[", port_name (ntohs (udp->dest))));
PrMac (eth->dest);
DEBUGP (("]"));
if (dhcp->ciaddr)
{
DEBUGP ((" ci="));
PrIP (dhcp->ciaddr);
}
if (dhcp->yiaddr)
{
DEBUGP ((" yi="));
PrIP (dhcp->yiaddr);
}
if (dhcp->siaddr)
{
DEBUGP ((" si="));
PrIP (dhcp->siaddr);
}
if (dhcp->hlen == sizeof (MACADDR))
{
DEBUGP ((" ch="));
PrMac (dhcp->chaddr);
}
DEBUGP ((" xid=0x%08x", ntohl (dhcp->xid)));
if (ntohl (dhcp->magic) != 0x63825363)
DEBUGP ((" ma=0x%08x", ntohl (dhcp->magic)));
if (dhcp->htype != 1)
DEBUGP ((" htype=%d", dhcp->htype));
if (dhcp->hops)
DEBUGP ((" hops=%d", dhcp->hops));
if (ntohs (dhcp->secs))
DEBUGP ((" secs=%d", ntohs (dhcp->secs)));
if (ntohs (dhcp->flags))
DEBUGP ((" flags=0x%04x", ntohs (dhcp->flags)));
// extra stuff
if (ip->version_len != 0x45)
DEBUGP ((" vl=0x%02x", ip->version_len));
if (ntohs (ip->tot_len) != sizeof (IPHDR) + sizeof (UDPHDR) + sizeof (DHCP) + optlen)
DEBUGP ((" tl=%d", ntohs (ip->tot_len)));
if (ntohs (udp->len) != sizeof (UDPHDR) + sizeof (DHCP) + optlen)
DEBUGP ((" ul=%d", ntohs (udp->len)));
if (ip->tos)
DEBUGP ((" tos=0x%02x", ip->tos));
if (ntohs (ip->id))
DEBUGP ((" id=0x%04x", ntohs (ip->id)));
if (ntohs (ip->frag_off))
DEBUGP ((" frag_off=0x%04x", ntohs (ip->frag_off)));
DEBUGP ((" ttl=%d", ip->ttl));
DEBUGP ((" ic=0x%04x [0x%04x]", ntohs (ip->check),
ip_checksum ((UCHAR*)ip, sizeof (IPHDR))));
DEBUGP ((" uc=0x%04x [0x%04x/%d]", ntohs (udp->check),
udp_checksum ((UCHAR *) udp,
sizeof (UDPHDR) + sizeof (DHCP) + optlen,
(UCHAR *) &ip->saddr,
(UCHAR *) &ip->daddr),
optlen));
// Options
{
const UCHAR *opt = (UCHAR *) (dhcp + 1);
int i;
DEBUGP ((" OPT"));
for (i = 0; i < optlen; ++i)
{
const UCHAR data = opt[i];
DEBUGP ((".%d", data));
}
}
}
#endif /* DBG */
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