arpdump.c

/*
 * arpdump.c - dump arp table
 * vinod
 */ 
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#include <err.h>

#include <sys/param.h>
#include <sys/sockio.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/route.h>
#include <net/iso88025.h>

#include <net/arpmon.h>

#include <netinet/in.h>
#include <netinet/if_ether.h>

#include <arpa/inet.h>

typedef void (action_fn)(struct sockaddr_dl *sdl,
        struct sockaddr_inarp *s_in, struct rt_msghdr *rtm);
static action_fn print_entry;

static int search(u_long addr, action_fn *action);
static int get(char *host);
static struct sockaddr_inarp *getaddr(char *host);

static char *rifname;
static int nflag = 1;       /* no reverse dns lookups */

/*
 * Display an arp entry
 */
static time_t   expire_time;
static char lifname[IF_NAMESIZE];
static int64_t lifindex = -1;

static void
print_entry(struct sockaddr_dl *sdl,
        struct sockaddr_inarp *addr, struct rt_msghdr *rtm)
{
        const char *host;
        struct hostent *hp;
        struct iso88025_sockaddr_dl_data *trld;
        int seg;

        if (nflag == 0)
                hp = gethostbyaddr((caddr_t)&(addr->sin_addr),
                    sizeof addr->sin_addr, AF_INET);
        else
                hp = 0;
        if (hp) 
                host = hp->h_name;
        else {  
                host = "?";
                if (h_errno == TRY_AGAIN)
                        nflag = 1;
        }
        printf("%s (%s) at ", host, inet_ntoa(addr->sin_addr));
        if (sdl->sdl_alen) {
                if ((sdl->sdl_type == IFT_ETHER ||
                    sdl->sdl_type == IFT_L2VLAN ||
                    sdl->sdl_type == IFT_BRIDGE) &&
                    sdl->sdl_alen == ETHER_ADDR_LEN)
                        printf("%s", ether_ntoa((struct ether_addr *)LLADDR(sdl)));
                else {
                        int n = sdl->sdl_nlen > 0 ? sdl->sdl_nlen + 1 : 0;

                        printf("%s", link_ntoa(sdl) + n);
                }
        } else
                printf("(incomplete)");
        if (sdl->sdl_index != lifindex &&
            if_indextoname(sdl->sdl_index, lifname) != NULL) {
                lifindex = sdl->sdl_index;
                printf(" on %s", lifname);
        } else if (sdl->sdl_index == lifindex)
                printf(" on %s", lifname);
        if (rtm->rtm_rmx.rmx_expire == 0)
                printf(" permanent");
        else {
                static struct timespec tp;
                if (tp.tv_sec == 0)
                        clock_gettime(CLOCK_MONOTONIC, &tp);
                if ((expire_time = rtm->rtm_rmx.rmx_expire - tp.tv_sec) > 0)
                        printf(" expires in %d seconds", (int)expire_time);
                else
                        printf(" expired");
        }
        if (addr->sin_other & SIN_PROXY)
                printf(" published (proxy only)");
        if (rtm->rtm_flags & RTF_ANNOUNCE)
                printf(" published");
        switch(sdl->sdl_type) {
        case IFT_ETHER:
                printf(" [ethernet]");
                break;
        case IFT_ISO88025:
                printf(" [token-ring]");
                trld = SDL_ISO88025(sdl);
                if (trld->trld_rcf != 0) {
                        printf(" rt=%x", ntohs(trld->trld_rcf));
                        for (seg = 0;
                             seg < ((TR_RCF_RIFLEN(trld->trld_rcf) - 2 ) / 2);
                             seg++)
                                printf(":%x", ntohs(*(trld->trld_route[seg])));
                }
                break;
        case IFT_FDDI:
                printf(" [fddi]");
                break;
        case IFT_ATM:
                printf(" [atm]");
                break;
        case IFT_L2VLAN:
                printf(" [vlan]");
                break;
        case IFT_IEEE1394:
                printf(" [firewire]");
                break;
        case IFT_BRIDGE:
                printf(" [bridge]");
                break;
        default:
                break;
        }

        printf("\n");
}

/*
 * Given a hostname, fills up a (static) struct sockaddr_inarp with
 * the address of the host and returns a pointer to the
 * structure.
 */
static struct sockaddr_inarp *
getaddr(char *host)
{
	struct hostent *hp;
	static struct sockaddr_inarp reply;

	bzero(&reply, sizeof(reply));
	reply.sin_len = sizeof(reply);
	reply.sin_family = AF_INET;
	reply.sin_addr.s_addr = inet_addr(host);
	if (reply.sin_addr.s_addr == INADDR_NONE) {
		if (!(hp = gethostbyname(host))) {
			warnx("%s: %s", host, hstrerror(h_errno));
			return (NULL);
		}
		bcopy((char *)hp->h_addr, (char *)&reply.sin_addr,
				sizeof reply.sin_addr);
	}
	return (&reply);
}

static int
get(char *host)
{
	struct sockaddr_inarp *addr;

	addr = getaddr(host);
	if (addr == NULL)
		return (1);
	if (0 == search(addr->sin_addr.s_addr, print_entry)) {
		printf("%s (%s) -- no entry",
				host, inet_ntoa(addr->sin_addr));
		if (rifname)
			printf(" on %s", rifname);
		printf("\n");
		return (1);
	}
	return (0);
}

/*
 * Search the arp table and do some action on matching entries
 */
static int 
search(u_long addr, action_fn *action)
{
        int mib[6];
        size_t needed;
        char *lim, *buf, *next;
        struct rt_msghdr *rtm;
        struct sockaddr_inarp *sin2;
        struct sockaddr_dl *sdl;
        char ifname[IF_NAMESIZE];
        int st, found_entry = 0;

        mib[0] = CTL_NET;
        mib[1] = PF_ROUTE;
        mib[2] = 0;
        mib[3] = AF_INET;
        mib[4] = NET_RT_FLAGS;
#ifdef RTF_LLINFO
        mib[5] = RTF_LLINFO;
#else
        mib[5] = 0;
#endif  
        if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
                err(1, "route-sysctl-estimate");
        if (needed == 0)        /* empty table */
                return 0;
        buf = NULL;
        for (;;) {
                buf = reallocf(buf, needed);
                if (buf == NULL)
                        errx(1, "could not reallocate memory");
                st = sysctl(mib, 6, buf, &needed, NULL, 0);
                if (st == 0 || errno != ENOMEM)
                        break;
                needed += needed / 8;
        }
        if (st == -1)
                err(1, "actual retrieval of routing table");
        lim = buf + needed;
        for (next = buf; next < lim; next += rtm->rtm_msglen) {
                rtm = (struct rt_msghdr *)next;
                sin2 = (struct sockaddr_inarp *)(rtm + 1);
                sdl = (struct sockaddr_dl *)((char *)sin2 + SA_SIZE(sin2));
                if (rifname && if_indextoname(sdl->sdl_index, ifname) &&
                    strcmp(ifname, rifname))
                        continue;
                if (addr) {
                        if (addr != sin2->sin_addr.s_addr)
                                continue;
                        found_entry = 1;
                }
                (*action)(sdl, sin2, rtm);
        }
        free(buf);
        return (found_entry);
}


int
main ( int argc, char *argv[] )
{
	argc = argc;

	if ( argv[1] )
		get(argv[1]);
	else
		search(0, print_entry);

	return ( EXIT_SUCCESS );
}