busybox/networking/udhcp/script.c

/* script.c
 *
 * Functions to call the DHCP client notification scripts
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/wait.h>

#include "common.h"
#include "options.h"
#include "dhcpd.h"
#include "dhcpc.h"

/* get a rough idea of how long an option will be (rounding up...) */
static const int max_option_length[] = {
	[OPTION_IP] =		sizeof("255.255.255.255 "),
	[OPTION_IP_PAIR] =	sizeof("255.255.255.255 ") * 2,
	[OPTION_STRING] =	1,
	[OPTION_BOOLEAN] =	sizeof("yes "),
	[OPTION_U8] =		sizeof("255 "),
	[OPTION_U16] =		sizeof("65535 "),
	[OPTION_S16] =		sizeof("-32768 "),
	[OPTION_U32] =		sizeof("4294967295 "),
	[OPTION_S32] =		sizeof("-2147483684 "),
};


static inline int upper_length(int length, int opt_index)
{
	return max_option_length[opt_index] *
		(length / option_lengths[opt_index]);
}


static int sprintip(char *dest, char *pre, uint8_t *ip)
{
	return sprintf(dest, "%s%d.%d.%d.%d", pre, ip[0], ip[1], ip[2], ip[3]);
}


/* really simple implementation, just count the bits */
static int mton(struct in_addr *mask)
{
	int i;
	unsigned long bits = ntohl(mask->s_addr);
	/* too bad one can't check the carry bit, etc in c bit
	 * shifting */
	for (i = 0; i < 32 && !((bits >> i) & 1); i++);
	return 32 - i;
}


/* Fill dest with the text of option 'option'. */
static void fill_options(char *dest, uint8_t *option, struct dhcp_option *type_p)
{
	int type, optlen;
	uint16_t val_u16;
	int16_t val_s16;
	uint32_t val_u32;
	int32_t val_s32;
	int len = option[OPT_LEN - 2];

	dest += sprintf(dest, "%s=", type_p->name);

	type = type_p->flags & TYPE_MASK;
	optlen = option_lengths[type];
	for(;;) {
		switch (type) {
		case OPTION_IP_PAIR:
			dest += sprintip(dest, "", option);
			*(dest++) = '/';
			option += 4;
			optlen = 4;
		case OPTION_IP:	/* Works regardless of host byte order. */
			dest += sprintip(dest, "", option);
			break;
		case OPTION_BOOLEAN:
			dest += sprintf(dest, *option ? "yes" : "no");
			break;
		case OPTION_U8:
			dest += sprintf(dest, "%u", *option);
			break;
		case OPTION_U16:
			memcpy(&val_u16, option, 2);
			dest += sprintf(dest, "%u", ntohs(val_u16));
			break;
		case OPTION_S16:
			memcpy(&val_s16, option, 2);
			dest += sprintf(dest, "%d", ntohs(val_s16));
			break;
		case OPTION_U32:
			memcpy(&val_u32, option, 4);
			dest += sprintf(dest, "%lu", (unsigned long) ntohl(val_u32));
			break;
		case OPTION_S32:
			memcpy(&val_s32, option, 4);
			dest += sprintf(dest, "%ld", (long) ntohl(val_s32));
			break;
		case OPTION_STRING:
			memcpy(dest, option, len);
			dest[len] = '\0';
			return;	 /* Short circuit this case */
		}
		option += optlen;
		len -= optlen;
		if (len <= 0) break;
		dest += sprintf(dest, " ");
	}
}


/* put all the parameters into an environment */
static char **fill_envp(struct dhcpMessage *packet)
{
	int num_options = 0;
	int i, j;
	char **envp;
	uint8_t *temp;
	struct in_addr subnet;
	char over = 0;

	if (packet == NULL)
		num_options = 0;
	else {
		for (i = 0; dhcp_options[i].code; i++)
			if (get_option(packet, dhcp_options[i].code)) {
				num_options++;
				if (dhcp_options[i].code == DHCP_SUBNET)
					num_options++; /* for mton */
			}
		if (packet->siaddr) num_options++;
		if ((temp = get_option(packet, DHCP_OPTION_OVER)))
			over = *temp;
		if (!(over & FILE_FIELD) && packet->file[0]) num_options++;
		if (!(over & SNAME_FIELD) && packet->sname[0]) num_options++;
	}

	envp = xzalloc(sizeof(char *) * (num_options + 5));
	j = 0;
	envp[j++] = bb_xasprintf("interface=%s", client_config.interface);
	envp[j++] = bb_xasprintf("PATH=%s",
		getenv("PATH") ? : "/bin:/usr/bin:/sbin:/usr/sbin");
	envp[j++] = bb_xasprintf("HOME=%s", getenv("HOME") ? : "/");

	if (packet == NULL) return envp;

	envp[j] = xmalloc(sizeof("ip=255.255.255.255"));
	sprintip(envp[j++], "ip=", (uint8_t *) &packet->yiaddr);


	for (i = 0; dhcp_options[i].code; i++) {
		if (!(temp = get_option(packet, dhcp_options[i].code)))
			continue;
		envp[j] = xmalloc(upper_length(temp[OPT_LEN - 2],
			dhcp_options[i].flags & TYPE_MASK) + strlen(dhcp_options[i].name) + 2);
		fill_options(envp[j++], temp, &dhcp_options[i]);

		/* Fill in a subnet bits option for things like /24 */
		if (dhcp_options[i].code == DHCP_SUBNET) {
			memcpy(&subnet, temp, 4);
			envp[j++] = bb_xasprintf("mask=%d", mton(&subnet));
		}
	}
	if (packet->siaddr) {
		envp[j] = xmalloc(sizeof("siaddr=255.255.255.255"));
		sprintip(envp[j++], "siaddr=", (uint8_t *) &packet->siaddr);
	}
	if (!(over & FILE_FIELD) && packet->file[0]) {
		/* watch out for invalid packets */
		packet->file[sizeof(packet->file) - 1] = '\0';
		envp[j++] = bb_xasprintf("boot_file=%s", packet->file);
	}
	if (!(over & SNAME_FIELD) && packet->sname[0]) {
		/* watch out for invalid packets */
		packet->sname[sizeof(packet->sname) - 1] = '\0';
		envp[j++] = bb_xasprintf("sname=%s", packet->sname);
	}
	return envp;
}


/* Call a script with a par file and env vars */
void udhcp_run_script(struct dhcpMessage *packet, const char *name)
{
	int pid;
	char **envp, **curr;

	if (client_config.script == NULL)
		return;

	DEBUG(LOG_INFO, "vforking and execle'ing %s", client_config.script);

	envp = fill_envp(packet);
	/* call script */
	pid = vfork();
	if (pid) {
		waitpid(pid, NULL, 0);
		for (curr = envp; *curr; curr++) free(*curr);
		free(envp);
		return;
	} else if (pid == 0) {
		/* close fd's? */

		/* exec script */
		execle(client_config.script, client_config.script,
		       name, NULL, envp);
		LOG(LOG_ERR, "script %s failed: %m", client_config.script);
		exit(1);
	}
}