ndhc/ifchange.c
Nicholas J. Kain 484a9c516b Use stb_snprintf instead of libc snprintf.
This gives us consistent behavior and stb_snprintf is async signal
safe.
2022-03-07 20:42:00 -05:00

324 lines
10 KiB
C

// Copyright 2004-2018 Nicholas J. Kain <njkain at gmail dot com>
// SPDX-License-Identifier: MIT
#include <string.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <errno.h>
#include <limits.h>
#include "nk/stb_sprintf.h"
#include "nk/log.h"
#include "nk/io.h"
#include "options.h"
#include "ndhc.h"
#include "dhcp.h"
#include "options.h"
#include "arp.h"
#include "ifchange.h"
static struct dhcpmsg cfg_packet; // Copy of the current configuration packet.
static int ifcmd_raw(char *buf, size_t buflen, const char *optname,
char *optdata, size_t optlen)
{
if (!optdata) {
log_line("%s: (%s) '%s' option has no data",
client_config.interface, __func__, optname);
return -1;
}
if (optlen > INT_MAX) {
log_line("%s: (%s) '%s' option optlen out of bounds",
client_config.interface, __func__, optname);
return -1;
}
if (buflen < strlen(optname) + optlen + 3) {
log_line("%s: (%s) '%s' option buf too short",
client_config.interface, __func__, optname);
return -1;
}
int ioptlen = (int)optlen;
ssize_t olen = stbsp_snprintf(buf, buflen, "%s:%.*s;",
optname, ioptlen, optdata);
if (olen < 0 || (size_t)olen > buflen) {
log_line("%s: (%s) '%s' option would truncate, so it was dropped.",
client_config.interface, __func__, optname);
memset(buf, 0, buflen);
return -1;
}
return olen;
}
static int ifcmd_bytes(char *buf, size_t buflen, const char *optname,
uint8_t *optdata, size_t optlen)
{
return ifcmd_raw(buf, buflen, optname, (char *)optdata, optlen);
}
static int ifcmd_u8(char *buf, size_t buflen, const char *optname,
uint8_t *optdata, size_t optlen)
{
if (!optdata || optlen < 1)
return -1;
char numbuf[16];
uint8_t c = optdata[0];
ssize_t olen = stbsp_snprintf(numbuf, sizeof numbuf, "%c", c);
if (olen < 0 || (size_t)olen > sizeof numbuf)
return -1;
return ifcmd_raw(buf, buflen, optname, numbuf, strlen(numbuf));
}
static int ifcmd_u16(char *buf, size_t buflen, const char *optname,
uint8_t *optdata, size_t optlen)
{
if (!optdata || optlen < 2)
return -1;
char numbuf[16];
uint16_t v;
memcpy(&v, optdata, 2);
v = ntohs(v);
ssize_t olen = stbsp_snprintf(numbuf, sizeof numbuf, "%hu", v);
if (olen < 0 || (size_t)olen > sizeof numbuf)
return -1;
return ifcmd_raw(buf, buflen, optname, numbuf, strlen(numbuf));
}
static int ifcmd_s32(char *buf, size_t buflen, const char *optname,
uint8_t *optdata, size_t optlen)
{
if (!optdata || optlen < 4)
return -1;
char numbuf[16];
uint32_t v;
memcpy(&v, optdata, 4);
v = ntohl(v);
ssize_t olen = stbsp_snprintf(numbuf, sizeof numbuf, "%d", v);
if (olen < 0 || (size_t)olen > sizeof numbuf)
return -1;
return ifcmd_raw(buf, buflen, optname, numbuf, strlen(numbuf));
}
static int ifcmd_ip(char *buf, size_t buflen, const char *optname,
uint8_t *optdata, size_t optlen)
{
if (!optdata || optlen < 4)
return -1;
char ipbuf[INET_ADDRSTRLEN];
inet_ntop(AF_INET, optdata, ipbuf, sizeof ipbuf);
return ifcmd_raw(buf, buflen, optname, ipbuf, strlen(ipbuf));
}
static int ifcmd_iplist(char *out, size_t outlen, const char *optname,
uint8_t *optdata, size_t optlen)
{
char buf[2048];
char ipbuf[INET_ADDRSTRLEN];
size_t bufoff = 0;
size_t optoff = 0;
if (!optdata || optlen < 4)
return -1;
inet_ntop(AF_INET, optdata + optoff, ipbuf, sizeof ipbuf);
ssize_t wc = stbsp_snprintf(buf + bufoff, sizeof buf, "%s", ipbuf);
if (wc < 0 || (size_t)wc > sizeof buf)
return -1;
optoff += 4;
bufoff += (size_t)wc;
while (optlen >= 4 + optoff) {
inet_ntop(AF_INET, optdata + optoff, ipbuf, sizeof ipbuf);
wc = stbsp_snprintf(buf + bufoff, sizeof buf, ",%s", ipbuf);
if (wc < 0 || (size_t)wc > sizeof buf)
return -1;
optoff += 4;
bufoff += (size_t)wc;
}
return ifcmd_raw(out, outlen, optname, buf, strlen(buf));
}
static int ifchd_cmd(char *b, size_t bl, uint8_t *od,
size_t ol, uint8_t code)
{
switch (code) {
case DCODE_ROUTER: return ifcmd_ip(b, bl, "routr", od, ol);
case DCODE_DNS: return ifcmd_iplist(b, bl, "dns", od, ol);
case DCODE_LPRSVR: return ifcmd_iplist(b, bl, "lpr", od, ol);
case DCODE_NTPSVR: return ifcmd_iplist(b, bl, "ntp", od, ol);
case DCODE_WINS: return ifcmd_iplist(b, bl, "wins", od, ol);
case DCODE_HOSTNAME: return ifcmd_bytes(b, bl, "host", od, ol);
case DCODE_DOMAIN: return ifcmd_bytes(b, bl, "dom", od, ol);
case DCODE_TIMEZONE: return ifcmd_s32(b, bl, "tzone", od, ol);
case DCODE_MTU: return ifcmd_u16(b, bl, "mtu", od, ol);
case DCODE_IPTTL: return ifcmd_u8(b, bl, "ipttl", od, ol);
default: break;
}
log_line("%s: Invalid option code (%c) for ifchd cmd.",
client_config.interface, code);
return -1;
}
static int ifchwrite(const char *buf, size_t count)
{
ssize_t r = safe_write(ifchSock[0], buf, count);
if (r < 0 || (size_t)r != count) {
log_line("%s: (%s) write failed: %zd", client_config.interface, __func__, r);
return -1;
}
char data[256], control[256];
struct iovec iov = {
.iov_base = data,
.iov_len = sizeof data - 1,
};
struct msghdr msg = {
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = control,
.msg_controllen = sizeof control
};
r = safe_recvmsg(ifchSock[0], &msg, 0);
if (r == 0) {
// Remote end hung up.
exit(EXIT_SUCCESS);
} else if (r < 0) {
suicide("%s: (%s) recvmsg failed: %s", client_config.interface,
__func__, strerror(errno));
}
data[iov.iov_len] = '\0';
if (r == 1 && data[0] == '+')
return 0;
return -1;
}
bool ifchange_carrier_isup(void)
{
char buf[256];
stbsp_snprintf(buf, sizeof buf, "carrier:;");
return ifchwrite(buf, strlen(buf)) == 0;
}
int ifchange_deconfig(struct client_state_t *cs)
{
char buf[256];
int ret = -1;
if (cs->ifDeconfig)
return 0;
stbsp_snprintf(buf, sizeof buf, "ip4:0.0.0.0,255.255.255.255;");
log_line("%s: Resetting IP configuration.", client_config.interface);
ret = ifchwrite(buf, strlen(buf));
if (ret >= 0) {
cs->ifDeconfig = 1;
memset(&cfg_packet, 0, sizeof cfg_packet);
}
return ret;
}
static size_t send_client_ip(char *out, size_t olen,
struct dhcpmsg *packet)
{
uint8_t optdata[MAX_DOPT_SIZE], olddata[MAX_DOPT_SIZE];
char ip[INET_ADDRSTRLEN], sn[INET_ADDRSTRLEN], bc[INET_ADDRSTRLEN];
size_t optlen, oldlen;
bool change_ipaddr = false;
bool have_subnet = false;
bool change_subnet = false;
bool have_bcast = false;
bool change_bcast = false;
if (memcmp(&packet->yiaddr, &cfg_packet.yiaddr, sizeof packet->yiaddr))
change_ipaddr = true;
inet_ntop(AF_INET, &packet->yiaddr, ip, sizeof ip);
optlen = get_dhcp_opt(packet, DCODE_SUBNET, optdata, sizeof optdata);
if (optlen >= 4) {
have_subnet = true;
inet_ntop(AF_INET, optdata, sn, sizeof sn);
oldlen = get_dhcp_opt(&cfg_packet, DCODE_SUBNET, olddata,
sizeof olddata);
if (oldlen != optlen || memcmp(optdata, olddata, optlen))
change_subnet = true;
}
optlen = get_dhcp_opt(packet, DCODE_BROADCAST, optdata, sizeof optdata);
if (optlen >= 4) {
have_bcast = true;
inet_ntop(AF_INET, optdata, bc, sizeof bc);
oldlen = get_dhcp_opt(&cfg_packet, DCODE_BROADCAST, olddata,
sizeof olddata);
if (oldlen != optlen || memcmp(optdata, olddata, optlen))
change_bcast = true;
}
// Nothing to change.
if (!change_ipaddr && !change_subnet && !change_bcast)
return 0;
if (!have_subnet) {
static char snClassC[] = "255.255.255.0";
log_line("%s: Server did not send a subnet mask. Assuming 255.255.255.0.",
client_config.interface);
memcpy(sn, snClassC, sizeof snClassC);
}
int snlen;
if (have_bcast) {
snlen = stbsp_snprintf(out, olen, "ip4:%s,%s,%s;", ip, sn, bc);
} else {
snlen = stbsp_snprintf(out, olen, "ip4:%s,%s;", ip, sn);
}
if (snlen < 0 || (size_t)snlen > olen) {
log_line("%s: (%s) ip4 command would truncate so it was dropped.",
client_config.interface, __func__);
memset(out, 0, olen);
return 0;
}
return (size_t)snlen;
}
static size_t send_cmd(char *out, size_t olen,
struct dhcpmsg *packet, uint8_t code)
{
uint8_t optdata[MAX_DOPT_SIZE], olddata[MAX_DOPT_SIZE];
size_t optlen, oldlen;
optlen = get_dhcp_opt(packet, code, optdata, sizeof optdata);
if (!optlen)
return 0;
oldlen = get_dhcp_opt(&cfg_packet, code, olddata, sizeof olddata);
if (oldlen == optlen && !memcmp(optdata, olddata, optlen))
return 0;
int r = ifchd_cmd(out, olen, optdata, optlen, code);
return r > 0 ? (size_t)r : 0;
}
int ifchange_bind(struct client_state_t *cs, struct dhcpmsg *packet)
{
char buf[2048];
size_t bo;
int ret = -1;
memset(buf, 0, sizeof buf);
bo = send_client_ip(buf, sizeof buf, packet);
bo += send_cmd(buf + bo, sizeof buf - bo, packet, DCODE_ROUTER);
bo += send_cmd(buf + bo, sizeof buf - bo, packet, DCODE_DNS);
bo += send_cmd(buf + bo, sizeof buf - bo, packet, DCODE_HOSTNAME);
bo += send_cmd(buf + bo, sizeof buf - bo, packet, DCODE_DOMAIN);
bo += send_cmd(buf + bo, sizeof buf - bo, packet, DCODE_MTU);
bo += send_cmd(buf + bo, sizeof buf - bo, packet, DCODE_WINS);
if (bo) {
log_line("%s: bind command: '%s'", client_config.interface, buf);
ret = ifchwrite(buf, bo);
}
if (ret >= 0) {
cs->ifDeconfig = 0;
memcpy(&cfg_packet, packet, sizeof cfg_packet);
}
return ret;
}