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circuitpython/shared/netutils/dhcpserver.c

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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2018-2019 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
// For DHCP specs see:
// https://www.ietf.org/rfc/rfc2131.txt
// https://tools.ietf.org/html/rfc2132 -- DHCP Options and BOOTP Vendor Extensions
#include <stdio.h>
#include <string.h>
#include "py/mperrno.h"
#include "py/mphal.h"
#include "lwip/opt.h"
// Used in CIRCUITPY without MICROPY_PY_LWIP
#if LWIP_UDP
#include "shared/netutils/dhcpserver.h"
#include "lwip/udp.h"
#define DHCPDISCOVER (1)
#define DHCPOFFER (2)
#define DHCPREQUEST (3)
#define DHCPDECLINE (4)
#define DHCPACK (5)
#define DHCPNACK (6)
#define DHCPRELEASE (7)
#define DHCPINFORM (8)
#define DHCP_OPT_PAD (0)
#define DHCP_OPT_SUBNET_MASK (1)
#define DHCP_OPT_ROUTER (3)
#define DHCP_OPT_DNS (6)
#define DHCP_OPT_HOST_NAME (12)
#define DHCP_OPT_REQUESTED_IP (50)
#define DHCP_OPT_IP_LEASE_TIME (51)
#define DHCP_OPT_MSG_TYPE (53)
#define DHCP_OPT_SERVER_ID (54)
#define DHCP_OPT_PARAM_REQUEST_LIST (55)
#define DHCP_OPT_MAX_MSG_SIZE (57)
#define DHCP_OPT_VENDOR_CLASS_ID (60)
#define DHCP_OPT_CLIENT_ID (61)
#define DHCP_OPT_END (255)
#define PORT_DHCP_SERVER (67)
#define PORT_DHCP_CLIENT (68)
#define DEFAULT_DNS MAKE_IP4(192, 168, 4, 1)
#define DEFAULT_LEASE_TIME_S (24 * 60 * 60) // in seconds
#define MAC_LEN (6)
#define MAKE_IP4(a, b, c, d) ((a) << 24 | (b) << 16 | (c) << 8 | (d))
typedef struct {
uint8_t op; // message opcode
uint8_t htype; // hardware address type
uint8_t hlen; // hardware address length
uint8_t hops;
uint32_t xid; // transaction id, chosen by client
uint16_t secs; // client seconds elapsed
uint16_t flags;
uint8_t ciaddr[4]; // client IP address
uint8_t yiaddr[4]; // your IP address
uint8_t siaddr[4]; // next server IP address
uint8_t giaddr[4]; // relay agent IP address
uint8_t chaddr[16]; // client hardware address
uint8_t sname[64]; // server host name
uint8_t file[128]; // boot file name
uint8_t options[312]; // optional parameters, variable, starts with magic
} dhcp_msg_t;
static int dhcp_socket_new_dgram(struct udp_pcb **udp, void *cb_data, udp_recv_fn cb_udp_recv) {
// family is AF_INET
// type is SOCK_DGRAM
*udp = udp_new();
if (*udp == NULL) {
return -MP_ENOMEM;
}
// Register callback
udp_recv(*udp, cb_udp_recv, (void *)cb_data);
return 0; // success
}
static void dhcp_socket_free(struct udp_pcb **udp) {
if (*udp != NULL) {
udp_remove(*udp);
*udp = NULL;
}
}
static int dhcp_socket_bind(struct udp_pcb **udp, uint32_t ip, uint16_t port) {
ip_addr_t addr;
IP4_ADDR(&addr, ip >> 24 & 0xff, ip >> 16 & 0xff, ip >> 8 & 0xff, ip & 0xff);
// TODO convert lwIP errors to errno
return udp_bind(*udp, &addr, port);
}
static int dhcp_socket_sendto(struct udp_pcb **udp, struct netif *netif, const void *buf, size_t len, uint32_t ip, uint16_t port) {
if (len > 0xffff) {
len = 0xffff;
}
struct pbuf *p = pbuf_alloc(PBUF_TRANSPORT, len, PBUF_RAM);
if (p == NULL) {
return -MP_ENOMEM;
}
memcpy(p->payload, buf, len);
ip_addr_t dest;
IP4_ADDR(&dest, ip >> 24 & 0xff, ip >> 16 & 0xff, ip >> 8 & 0xff, ip & 0xff);
err_t err;
if (netif != NULL) {
err = udp_sendto_if(*udp, p, &dest, port, netif);
} else {
err = udp_sendto(*udp, p, &dest, port);
}
pbuf_free(p);
if (err != ERR_OK) {
return err;
}
return len;
}
static uint8_t *opt_find(uint8_t *opt, uint8_t cmd) {
for (int i = 0; i < 308 && opt[i] != DHCP_OPT_END;) {
if (opt[i] == cmd) {
return &opt[i];
}
i += 2 + opt[i + 1];
}
return NULL;
}
static void opt_write_n(uint8_t **opt, uint8_t cmd, size_t n, const void *data) {
uint8_t *o = *opt;
*o++ = cmd;
*o++ = n;
memcpy(o, data, n);
*opt = o + n;
}
static void opt_write_u8(uint8_t **opt, uint8_t cmd, uint8_t val) {
uint8_t *o = *opt;
*o++ = cmd;
*o++ = 1;
*o++ = val;
*opt = o;
}
static void opt_write_u32(uint8_t **opt, uint8_t cmd, uint32_t val) {
uint8_t *o = *opt;
*o++ = cmd;
*o++ = 4;
*o++ = val >> 24;
*o++ = val >> 16;
*o++ = val >> 8;
*o++ = val;
*opt = o;
}
static void dhcp_server_process(void *arg, struct udp_pcb *upcb, struct pbuf *p, const ip_addr_t *src_addr, u16_t src_port) {
dhcp_server_t *d = arg;
(void)upcb;
(void)src_addr;
(void)src_port;
// This is around 548 bytes
dhcp_msg_t dhcp_msg;
#define DHCP_MIN_SIZE (240 + 3)
if (p->tot_len < DHCP_MIN_SIZE) {
goto ignore_request;
}
size_t len = pbuf_copy_partial(p, &dhcp_msg, sizeof(dhcp_msg), 0);
if (len < DHCP_MIN_SIZE) {
goto ignore_request;
}
dhcp_msg.op = DHCPOFFER;
memcpy(&dhcp_msg.yiaddr, &d->ip.addr, 4);
uint8_t *opt = (uint8_t *)&dhcp_msg.options;
opt += 4; // assume magic cookie: 99, 130, 83, 99
switch (opt[2]) {
case DHCPDISCOVER: {
int yi = DHCPS_MAX_IP;
for (int i = 0; i < DHCPS_MAX_IP; ++i) {
if (memcmp(d->lease[i].mac, dhcp_msg.chaddr, MAC_LEN) == 0) {
// MAC match, use this IP address
yi = i;
break;
}
if (yi == DHCPS_MAX_IP) {
// Look for a free IP address
if (memcmp(d->lease[i].mac, "\x00\x00\x00\x00\x00\x00", MAC_LEN) == 0) {
// IP available
yi = i;
}
uint32_t expiry = d->lease[i].expiry << 16 | 0xffff;
if ((int32_t)(expiry - mp_hal_ticks_ms()) < 0) {
// IP expired, reuse it
memset(d->lease[i].mac, 0, MAC_LEN);
yi = i;
}
}
}
if (yi == DHCPS_MAX_IP) {
// No more IP addresses left
goto ignore_request;
}
dhcp_msg.yiaddr[3] = DHCPS_BASE_IP + yi;
opt_write_u8(&opt, DHCP_OPT_MSG_TYPE, DHCPOFFER);
break;
}
case DHCPREQUEST: {
uint8_t *o = opt_find(opt, DHCP_OPT_REQUESTED_IP);
if (o == NULL) {
// Should be NACK
goto ignore_request;
}
if (memcmp(o + 2, &d->ip.addr, 3) != 0) {
// Should be NACK
goto ignore_request;
}
uint8_t yi = o[5] - DHCPS_BASE_IP;
if (yi >= DHCPS_MAX_IP) {
// Should be NACK
goto ignore_request;
}
if (memcmp(d->lease[yi].mac, dhcp_msg.chaddr, MAC_LEN) == 0) {
// MAC match, ok to use this IP address
} else if (memcmp(d->lease[yi].mac, "\x00\x00\x00\x00\x00\x00", MAC_LEN) == 0) {
// IP unused, ok to use this IP address
memcpy(d->lease[yi].mac, dhcp_msg.chaddr, MAC_LEN);
} else {
// IP already in use
// Should be NACK
goto ignore_request;
}
d->lease[yi].expiry = (mp_hal_ticks_ms() + DEFAULT_LEASE_TIME_S * 1000) >> 16;
dhcp_msg.yiaddr[3] = DHCPS_BASE_IP + yi;
opt_write_u8(&opt, DHCP_OPT_MSG_TYPE, DHCPACK);
LWIP_DEBUGF(DHCP_DEBUG, ("DHCPS: client connected: MAC=%02x:%02x:%02x:%02x:%02x:%02x IP=%u.%u.%u.%u\n",
dhcp_msg.chaddr[0], dhcp_msg.chaddr[1], dhcp_msg.chaddr[2], dhcp_msg.chaddr[3], dhcp_msg.chaddr[4], dhcp_msg.chaddr[5],
dhcp_msg.yiaddr[0], dhcp_msg.yiaddr[1], dhcp_msg.yiaddr[2], dhcp_msg.yiaddr[3]));
break;
}
default:
goto ignore_request;
}
opt_write_n(&opt, DHCP_OPT_SERVER_ID, 4, &d->ip.addr);
opt_write_n(&opt, DHCP_OPT_SUBNET_MASK, 4, &d->nm.addr);
opt_write_n(&opt, DHCP_OPT_ROUTER, 4, &d->ip.addr); // aka gateway; can have multiple addresses
opt_write_u32(&opt, DHCP_OPT_DNS, DEFAULT_DNS); // can have multiple addresses
opt_write_u32(&opt, DHCP_OPT_IP_LEASE_TIME, DEFAULT_LEASE_TIME_S);
*opt++ = DHCP_OPT_END;
struct netif *netif = ip_current_input_netif();
dhcp_socket_sendto(&d->udp, netif, &dhcp_msg, opt - (uint8_t *)&dhcp_msg, 0xffffffff, PORT_DHCP_CLIENT);
ignore_request:
pbuf_free(p);
}
void dhcp_server_init(dhcp_server_t *d, ip_addr_t *ip, ip_addr_t *nm) {
ip_addr_copy(d->ip, *ip);
ip_addr_copy(d->nm, *nm);
memset(d->lease, 0, sizeof(d->lease));
if (dhcp_socket_new_dgram(&d->udp, d, dhcp_server_process) != 0) {
return;
}
dhcp_socket_bind(&d->udp, 0, PORT_DHCP_SERVER);
}
void dhcp_server_deinit(dhcp_server_t *d) {
dhcp_socket_free(&d->udp);
}
#endif // MICROPY_PY_LWIP
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