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/* $OpenBSD: dhcp.c,v 1.4 2017/11/05 20:01:09 reyk Exp $ */
/*
* Copyright (c) 2017 Reyk Floeter <reyk@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include "proc.h"
#include "vmd.h"
#include "dhcp.h"
#include "virtio.h"
static const uint8_t broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
extern struct vmd *env;
ssize_t
dhcp_request(struct vionet_dev *dev, char *buf, size_t buflen, char **obuf)
{
unsigned char *respbuf = NULL, *op, *oe, dhcptype = 0;
ssize_t offset, respbuflen = 0;
struct packet_ctx pc;
struct dhcp_packet req, resp;
struct in_addr server_addr, mask, client_addr, requested_addr;
size_t resplen, o;
uint32_t ltime;
if (buflen < (ssize_t)(BOOTP_MIN_LEN + sizeof(struct ether_header)))
return (-1);
memset(&pc, 0, sizeof(pc));
if ((offset = decode_hw_header(buf, buflen, 0, &pc, HTYPE_ETHER)) < 0)
return (-1);
if (memcmp(pc.pc_smac, dev->mac, ETHER_ADDR_LEN) != 0 ||
memcmp(pc.pc_dmac, broadcast, ETHER_ADDR_LEN) != 0)
return (-1);
if ((offset = decode_udp_ip_header(buf, buflen, offset, &pc)) < 0)
return (-1);
if (ntohs(ss2sin(&pc.pc_src)->sin_port) != CLIENT_PORT ||
ntohs(ss2sin(&pc.pc_dst)->sin_port) != SERVER_PORT)
return (-1);
memset(&req, 0, sizeof(req));
memcpy(&req, buf + offset, buflen - offset);
if (req.op != BOOTREQUEST ||
req.htype != pc.pc_htype ||
req.hlen != ETHER_ADDR_LEN ||
memcmp(dev->mac, req.chaddr, req.hlen) != 0)
return (-1);
/* Ignore unsupported requests for now */
if (req.ciaddr.s_addr != 0 || req.file[0] != '\0' || req.hops != 0)
return (-1);
/* Get a few DHCP options (best effort as we fall back to BOOTP) */
if (memcmp(&req.options,
DHCP_OPTIONS_COOKIE, DHCP_OPTIONS_COOKIE_LEN) == 0) {
memset(&requested_addr, 0, sizeof(requested_addr));
op = req.options + DHCP_OPTIONS_COOKIE_LEN;
oe = req.options + sizeof(req.options);
while (*op != DHO_END && op < oe) {
if (op[0] == DHO_PAD) {
op++;
continue;
}
if (op + 1 + op[1] >= oe)
break;
if (op[0] == DHO_DHCP_MESSAGE_TYPE &&
op[1] == 1)
dhcptype = op[2];
else if (op[0] == DHO_DHCP_REQUESTED_ADDRESS &&
op[1] == sizeof(requested_addr))
memcpy(&requested_addr, &op[2],
sizeof(requested_addr));
op += 2 + op[1];
}
}
memset(&resp, 0, sizeof(resp));
resp.op = BOOTREPLY;
resp.htype = req.htype;
resp.hlen = req.hlen;
resp.xid = req.xid;
if ((client_addr.s_addr =
vm_priv_addr(&env->vmd_cfg.cfg_localprefix,
dev->vm_vmid, dev->idx, 1)) == 0)
return (-1);
memcpy(&resp.yiaddr, &client_addr,
sizeof(client_addr));
memcpy(&ss2sin(&pc.pc_dst)->sin_addr, &client_addr,
sizeof(client_addr));
ss2sin(&pc.pc_dst)->sin_port = htons(CLIENT_PORT);
if ((server_addr.s_addr =
vm_priv_addr(&env->vmd_cfg.cfg_localprefix,
dev->vm_vmid, dev->idx, 0)) == 0)
return (-1);
memcpy(&resp.siaddr, &server_addr,
sizeof(server_addr));
memcpy(&ss2sin(&pc.pc_src)->sin_addr, &server_addr,
sizeof(server_addr));
ss2sin(&pc.pc_src)->sin_port = htons(SERVER_PORT);
/* Packet is already allocated */
if (*obuf != NULL)
goto fail;
buflen = 0;
respbuflen = DHCP_MTU_MAX;
if ((respbuf = calloc(1, respbuflen)) == NULL)
goto fail;
memcpy(&pc.pc_dmac, dev->mac, sizeof(pc.pc_dmac));
memcpy(&resp.chaddr, dev->mac, resp.hlen);
memcpy(&pc.pc_smac, dev->mac, sizeof(pc.pc_smac));
pc.pc_smac[5]++;
if ((offset = assemble_hw_header(respbuf, respbuflen, 0,
&pc, HTYPE_ETHER)) < 0) {
log_debug("%s: assemble_hw_header failed", __func__);
goto fail;
}
/* BOOTP uses a 64byte vendor field instead of the DHCP options */
resplen = BOOTP_MIN_LEN;
/* Add BOOTP Vendor Extensions (DHCP options) */
o = 0;
memcpy(&resp.options,
DHCP_OPTIONS_COOKIE, DHCP_OPTIONS_COOKIE_LEN);
o+= DHCP_OPTIONS_COOKIE_LEN;
/* Did we receive a DHCP request or was it just BOOTP? */
if (dhcptype) {
/*
* There is no need for a real state machine as we always
* answer with the same client IP and options for the VM.
*/
if (dhcptype == DHCPDISCOVER)
dhcptype = DHCPOFFER;
else if (dhcptype == DHCPREQUEST &&
(requested_addr.s_addr == 0 ||
client_addr.s_addr == requested_addr.s_addr))
dhcptype = DHCPACK;
else
dhcptype = DHCPNAK;
resp.options[o++] = DHO_DHCP_MESSAGE_TYPE;
resp.options[o++] = sizeof(dhcptype);
memcpy(&resp.options[o], &dhcptype, sizeof(dhcptype));
o += sizeof(dhcptype);
/* Our lease never changes, use the maximum lease time */
resp.options[o++] = DHO_DHCP_LEASE_TIME;
resp.options[o++] = sizeof(ltime);
ltime = ntohl(0xffffffff);
memcpy(&resp.options[o], <ime, sizeof(ltime));
o += sizeof(ltime);
resp.options[o++] = DHO_DHCP_SERVER_IDENTIFIER;
resp.options[o++] = sizeof(server_addr);
memcpy(&resp.options[o], &server_addr, sizeof(server_addr));
o += sizeof(server_addr);
}
resp.options[o++] = DHO_DOMAIN_NAME_SERVERS;
resp.options[o++] = sizeof(server_addr);
memcpy(&resp.options[o], &server_addr, sizeof(server_addr));
o += sizeof(server_addr);
resp.options[o++] = DHO_SUBNET_MASK;
resp.options[o++] = sizeof(mask);
mask.s_addr = htonl(0xfffffffe);
memcpy(&resp.options[o], &mask, sizeof(mask));
o += sizeof(mask);
resp.options[o++] = DHO_ROUTERS;
resp.options[o++] = sizeof(server_addr);
memcpy(&resp.options[o], &server_addr, sizeof(server_addr));
o += sizeof(server_addr);
resp.options[o++] = DHO_DOMAIN_NAME_SERVERS;
resp.options[o++] = sizeof(server_addr);
memcpy(&resp.options[o], &server_addr, sizeof(server_addr));
o += sizeof(server_addr);
resp.options[o++] = DHO_END;
resplen = offsetof(struct dhcp_packet, options) + o;
/* Minimum packet size */
if (resplen < BOOTP_MIN_LEN)
resplen = BOOTP_MIN_LEN;
if ((offset = assemble_udp_ip_header(respbuf, respbuflen, offset, &pc,
(unsigned char *)&resp, resplen)) < 0) {
log_debug("%s: assemble_udp_ip_header failed", __func__);
goto fail;
}
memcpy(respbuf + offset, &resp, resplen);
respbuflen = offset + resplen;
*obuf = respbuf;
return (respbuflen);
fail:
free(respbuf);
return (0);
}
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