samba-mirror/ctdb/takeover/system.c

/* 
   ctdb recovery code

   Copyright (C) Ronnie Sahlberg  2007
   Copyright (C) Andrew Tridgell  2007

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   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; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"
#include "system/network.h"
#include "system/filesys.h"
#include "system/wait.h"
#include "../include/ctdb_private.h"
#include "lib/events/events.h"
#include <net/ethernet.h>
#include <net/if_arp.h>



/*
  send gratuitous arp reply after we have taken over an ip address

  saddr is the address we are trying to claim
  iface is the interface name we will be using to claim the address
 */
int ctdb_sys_send_arp(const struct sockaddr_in *saddr, const char *iface)
{
	int s, ret;
	struct sockaddr sa;
	struct ether_header *eh;
	struct arphdr *ah;
	struct ifreq if_hwaddr;
	unsigned char buffer[64]; /*minimum eth frame size */
	char *ptr;

	/* for now, we only handle AF_INET addresses */
	if (saddr->sin_family != AF_INET) {
		DEBUG(0,(__location__ " not an ipv4 address (family is %u)\n", saddr->sin_family));
		return -1;
	}

	s = socket(AF_INET, SOCK_PACKET, htons(ETHERTYPE_ARP));
	if (s == -1){
		DEBUG(0,(__location__ " failed to open raw socket\n"));
		return -1;
	}

	/* get the mac address */
	strcpy(if_hwaddr.ifr_name, iface);
	ret = ioctl(s, SIOCGIFHWADDR, &if_hwaddr);
	if ( ret < 0 ) {
		close(s);
		DEBUG(0,(__location__ " ioctl failed\n"));
		return -1;
	}
	if (if_hwaddr.ifr_hwaddr.sa_family != AF_LOCAL) {
		close(s);
		DEBUG(0,(__location__ " not an ethernet address\n"));
		return -1;
	}


	memset(buffer, 0 , 64);
	eh = (struct ether_header *)buffer;
	memset(eh->ether_dhost, 0xff, ETH_ALEN);
	memcpy(eh->ether_shost, if_hwaddr.ifr_hwaddr.sa_data, ETH_ALEN);
	eh->ether_type = htons(ETHERTYPE_ARP);

	ah = (struct arphdr *)&buffer[sizeof(struct ether_header)];
	ah->ar_hrd = htons(ARPHRD_ETHER);
	ah->ar_pro = htons(ETH_P_IP);
	ah->ar_hln = ETH_ALEN;
	ah->ar_pln = 4;

	/* send a gratious arp */
	ah->ar_op  = htons(ARPOP_REQUEST);
	ptr = (char *)&ah[1];
	memcpy(ptr, if_hwaddr.ifr_hwaddr.sa_data, ETH_ALEN);
	ptr+=ETH_ALEN;
	memcpy(ptr, &saddr->sin_addr, 4);	  
	ptr+=4;
	memset(ptr, 0, ETH_ALEN); 
	ptr+=ETH_ALEN;
	memcpy(ptr, &saddr->sin_addr, 4);	  
	ptr+=4;

	strncpy(sa.sa_data, iface, sizeof(sa.sa_data));
	ret = sendto(s, buffer, 64, 0, &sa, sizeof(sa));
	if (ret < 0 ){
		close(s);
		DEBUG(0,(__location__ " failed sendto\n"));
		return -1;
	}

	/* send unsolicited arp reply broadcast */
	ah->ar_op  = htons(ARPOP_REPLY);
	ptr = (char *)&ah[1];
	memcpy(ptr, if_hwaddr.ifr_hwaddr.sa_data, ETH_ALEN);
	ptr+=ETH_ALEN;
	memcpy(ptr, &saddr->sin_addr, 4);	  
	ptr+=4;
	memcpy(ptr, if_hwaddr.ifr_hwaddr.sa_data, ETH_ALEN);
	ptr+=ETH_ALEN;
	memcpy(ptr, &saddr->sin_addr, 4);	  
	ptr+=4;

	strncpy(sa.sa_data, iface, sizeof(sa.sa_data));
	ret = sendto(s, buffer, 64, 0, &sa, sizeof(sa));
	if (ret < 0 ){
		DEBUG(0,(__location__ " failed sendto\n"));
		return -1;
	}

	close(s);
	return 0;
}


/*
  uint16 checksum for n bytes
 */
static uint32_t uint16_checksum(uint16_t *data, size_t n)
{
	uint32_t sum=0;
	while (n>=2) {
		sum += (uint32_t)ntohs(*data);
		data++;
		n -= 2;
	}
	if (n == 1) {
		sum += (uint32_t)ntohs(*(uint8_t *)data);
	}
	return sum;
}

/*
  simple TCP checksum - assumes data is multiple of 2 bytes long
 */
static uint16_t tcp_checksum(uint16_t *data, size_t n, struct iphdr *ip)
{
	uint32_t sum = uint16_checksum(data, n);
	uint16_t sum2;
	sum += uint16_checksum((uint16_t *)&ip->saddr, sizeof(ip->saddr));
	sum += uint16_checksum((uint16_t *)&ip->daddr, sizeof(ip->daddr));
	sum += ip->protocol + n;
	sum = (sum & 0xFFFF) + (sum >> 16);
	sum = (sum & 0xFFFF) + (sum >> 16);
	sum2 = htons(sum);
	sum2 = ~sum2;
	if (sum2 == 0) {
		return 0xFFFF;
	}
	return sum2;
}

/*
  send tcp ack packet from the specified IP/port to the specified
  destination IP/port. 

  This is used to trigger the receiving host into sending its own ACK,
  which should trigger early detection of TCP reset by the client
  after IP takeover
 */
int ctdb_sys_send_ack(const struct sockaddr_in *dest, 
		      const struct sockaddr_in *src)
{
	int s, ret;
	uint32_t one = 1;
	struct {
		struct iphdr ip;
		struct tcphdr tcp;
	} pkt;

	/* for now, we only handle AF_INET addresses */
	if (src->sin_family != AF_INET || dest->sin_family != AF_INET) {
		DEBUG(0,(__location__ " not an ipv4 address\n"));
		return -1;
	}

	s = socket(AF_INET, SOCK_RAW, htons(IPPROTO_RAW));
	if (s == -1) {
		DEBUG(0,(__location__ " failed to open raw socket (%s)\n",
			 strerror(errno)));
		return -1;
	}

	ret = setsockopt(s, SOL_IP, IP_HDRINCL, &one, sizeof(one));
	if (ret != 0) {
		DEBUG(0,(__location__ " failed to setup IP headers (%s)\n",
			 strerror(errno)));
		close(s);
		return -1;
	}

	ZERO_STRUCT(pkt);
	pkt.ip.version  = 4;
	pkt.ip.ihl      = sizeof(pkt.ip)/4;
	pkt.ip.tot_len  = htons(sizeof(pkt));
	pkt.ip.ttl      = 255;
	pkt.ip.protocol = IPPROTO_TCP;
	pkt.ip.saddr    = src->sin_addr.s_addr;
	pkt.ip.daddr    = dest->sin_addr.s_addr;
	pkt.ip.check    = 0;

	pkt.tcp.source   = src->sin_port;
	pkt.tcp.dest     = dest->sin_port;
	pkt.tcp.ack      = 1;
	pkt.tcp.doff     = sizeof(pkt.tcp)/4;
	pkt.tcp.window   = htons(1234);
	pkt.tcp.check    = tcp_checksum((uint16_t *)&pkt.tcp, sizeof(pkt.tcp), &pkt.ip);

	ret = sendto(s, &pkt, sizeof(pkt), 0, dest, sizeof(*dest));
	if (ret != sizeof(pkt)) {
		DEBUG(0,(__location__ " failed sendto (%s)\n", strerror(errno)));
		close(s);
		return -1;
	}

	close(s);
	return 0;
}


/*
  see if we currently have an interface with the given IP

  we try to bind to it, and if that fails then we don't have that IP
  on an interface
 */
bool ctdb_sys_have_ip(const char *ip)
{
	struct sockaddr_in sin;
	int s;
	int ret;

	sin.sin_port = 0;
	inet_aton(ip, &sin.sin_addr);
	sin.sin_family = AF_INET;
	s = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (s == -1) {
		return false;
	}
	ret = bind(s, (struct sockaddr *)&sin, sizeof(sin));
	close(s);
	return ret == 0;
}

/*
  run the event script - varargs version
 */
static int ctdb_event_script_v(struct ctdb_context *ctdb, const char *fmt, va_list ap)
{
	char *options, *cmdstr;
	int ret;
	va_list ap2;
	struct stat st;

	if (stat(ctdb->takeover.event_script, &st) != 0 && 
	    errno == ENOENT) {
		DEBUG(0,("No event script found at '%s'\n", ctdb->takeover.event_script));
		return 0;
	}

	va_copy(ap2, ap);
	options  = talloc_vasprintf(ctdb, fmt, ap2);
	va_end(ap2);
	CTDB_NO_MEMORY(ctdb, options);

	cmdstr = talloc_asprintf(ctdb, "%s %s", ctdb->takeover.event_script, options);
	CTDB_NO_MEMORY(ctdb, cmdstr);

	ret = system(cmdstr);
	if (ret != -1) {
		ret = WEXITSTATUS(ret);
	}

	talloc_free(cmdstr);
	talloc_free(options);

	return ret;
}

/*
  run the event script
 */
int ctdb_event_script(struct ctdb_context *ctdb, const char *fmt, ...)
{
	va_list ap;
	int ret;

	va_start(ap, fmt);
	ret = ctdb_event_script_v(ctdb, fmt, ap);
	va_end(ap);

	return ret;
}


struct ctdb_event_script_state {
	struct ctdb_context *ctdb;
	pid_t child;
	void (*callback)(struct ctdb_context *, int, void *);
	int fd[2];
	void *private_data;
};

/* called when child is finished */
static void ctdb_event_script_handler(struct event_context *ev, struct fd_event *fde, 
				      uint16_t flags, void *p)
{
	struct ctdb_event_script_state *state = 
		talloc_get_type(p, struct ctdb_event_script_state);
	int status = -1;
	void (*callback)(struct ctdb_context *, int, void *) = state->callback;
	void *private_data = state->private_data;
	struct ctdb_context *ctdb = state->ctdb;

	waitpid(state->child, &status, 0);
	if (status != -1) {
		status = WEXITSTATUS(status);
	}
	talloc_set_destructor(state, NULL);
	talloc_free(state);
	callback(ctdb, status, private_data);
}

/*
  destroy a running event script
 */
static int event_script_destructor(struct ctdb_event_script_state *state)
{
	kill(state->child, SIGKILL);
	waitpid(state->child, NULL, 0);
	return 0;
}

/*
  run the event script in the background, calling the callback when 
  finished
 */
int ctdb_event_script_callback(struct ctdb_context *ctdb, 
			       TALLOC_CTX *mem_ctx,
			       void (*callback)(struct ctdb_context *, int, void *),
			       void *private_data,
			       const char *fmt, ...)
{
	struct ctdb_event_script_state *state;
	va_list ap;
	int ret;

	state = talloc(mem_ctx, struct ctdb_event_script_state);
	CTDB_NO_MEMORY(ctdb, state);

	state->ctdb = ctdb;
	state->callback = callback;
	state->private_data = private_data;
	
	ret = pipe(state->fd);
	if (ret != 0) {
		talloc_free(state);
		return -1;
	}

	state->child = fork();

	if (state->child == (pid_t)-1) {
		close(state->fd[0]);
		close(state->fd[1]);
		talloc_free(state);
		return -1;
	}

	if (state->child == 0) {
		close(state->fd[0]);
		ctdb_set_realtime(false);
		set_close_on_exec(state->fd[1]);
		va_start(ap, fmt);
		ret = ctdb_event_script_v(ctdb, fmt, ap);
		va_end(ap);
		_exit(ret);
	}

	talloc_set_destructor(state, event_script_destructor);

	close(state->fd[1]);

	event_add_fd(ctdb->ev, state, state->fd[0], EVENT_FD_READ|EVENT_FD_AUTOCLOSE,
		     ctdb_event_script_handler, state);

	return 0;
}