dhcpd.c

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/*      dhcpd 1.15 - Dynamic Host Configuration Protocol daemon.
 *                                                      Author: Kees J. Bot
 *                                                              11 Jun 1999
 */
#include <sys/types.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <time.h>
#include <limits.h>
#include <configfile.h>
#include <sys/ioctl.h>
#include <sys/asynchio.h>
#include <net/hton.h>
#include <net/gen/socket.h>
#include <net/gen/netdb.h>
#include <net/gen/in.h>
#include <net/gen/inet.h>
#include <net/gen/ether.h>
#include <net/gen/if_ether.h>
#include <net/gen/eth_hdr.h>
#include <net/gen/ip_hdr.h>
#include <net/gen/udp.h>
#include <net/gen/udp_hdr.h>
#include <net/gen/udp_io.h>
#include <net/gen/dhcp.h>
#include "arp.h"
#define EXTERN
#include "dhcpd.h"

char *configfile= PATH_DHCPCONF;
char *poolfile= PATH_DHCPPOOL;
static char *cachefile= PATH_DHCPCACHE;
static int qflag;               /* True if printing cached DHCP data. */
static int aflag, rflag;        /* True if adding or deleting pool addresses. */

#define BCAST_IP        HTONL(0xFFFFFFFFUL)

/* We try to play with up to this many networks. */
#define N_NETS          32
static unsigned n_nets;         /* Actual number of networks. */

void report(const char *label)
{
    static FILE *logfp;
    if(!logfp)
        logfp = fopen("/usr/log/dhcp.log", "w");
    if(logfp)
        fprintf(logfp, "%s: %s: %s\n", program, label, strerror(errno));
}

void fatal(const char *label)
{
    report(label);
    exit(1);
}

void *allocate(size_t size)
{
    void *mem;

    if ((mem= malloc(size)) == nil) fatal("Can't allocate memory");
    return mem;
}

/* Choose a DHCP xid based on the start time and network number.  Not really
 * random, but we don't have anything more random than the clock anyway.
 */
#define XID(np)         htonl(((u32_t) (np)->start << 8) | (np)->n)

static network_t *network[N_NETS];

int ifname2if(const char *name)
{
    /* Translate an interface name to a number, -1 if bad. */
    char *end;
    unsigned long n;

    if (*name++ != 'i' || *name++ != 'p') return -1;
    n= strtoul(name, &end, 10);
    if (end == name || *end != 0) return -1;
    if (n >= N_NETS) return -1;
    return n;
}

network_t *if2net(int n)
{
    /* Translate an interface number to a network struct. */
    int i;

    for (i= 0; i < n_nets; i++) {
        if (network[i]->n == n) return network[i];
    }
    return nil;
}

static ipaddr_t defaultmask(ipaddr_t ip)
{
    /* Compute netmask by the oldfashioned Class rules. */
    if (B(&ip)[0] < 0x80) return HTONL(0xFF000000UL);   /* Class A. */
    if (B(&ip)[0] < 0xC0) return HTONL(0xFFFF0000UL);   /* Class B. */
    if (B(&ip)[0] < 0xE0) return HTONL(0xFFFFFF00UL);   /* Class C. */
    return HTONL(0xFFFFFFFFUL);  /* Multicast?  Shouldn't happen... */
}

#define POOL_MAGIC      HTONL(0x81F85D00UL)

typedef struct pool {           /* Dynamic pool entry. */
        u32_t           magic;          /* Pool file magic number. */
        ipaddr_t        ip;             /* IP address. */
        u32_t           expire;         /* When does/did the lease expire? */
        u8_t            len;            /* Client ID length. */
        u8_t            unused[19];     /* Space for extensions. */
        u8_t            clid[CLID_MAX]; /* Client ID of current/last user. */
} pool_t;

static int openpool(int mode)
{
    /* Open the dynamic pool and lock it, return fd on success or -1. */
    int fd;
    struct flock lck;

    if ((fd= open(poolfile, mode, 0644)) < 0) {
        if (errno != ENOENT) fatal(poolfile);
        return -1;
    }
    if (mode != O_RDONLY) {
        lck.l_type= F_WRLCK;
        lck.l_whence= SEEK_SET;
        lck.l_start= 0;
        lck.l_len= 0;
        if (fcntl(fd, F_SETLKW, &lck) < 0) fatal(poolfile);
    }
    return fd;
}

static int readpool(int fd, pool_t *entry)
{
    /* Read one pool table entry, return true unless EOF. */
    ssize_t r;

    if ((r= read(fd, entry, sizeof(*entry))) < 0) fatal(poolfile);
    if (r == 0) return 0;

    if (r != sizeof(*entry) || entry->magic != POOL_MAGIC) {
        fprintf(stderr, "%s: %s: Pool table is corrupt\n",
            program, poolfile);
        close(fd);
        return 0;
    }
    return 1;
}

#if !__minix_vmd        /* No fsync() for Minix. */
#define fsync(fd)       sync()
#endif

static void writepool(int fd, pool_t *entry)
{
    /* (Over)write a pool table entry. */
    if (write(fd, entry, sizeof(*entry)) < 0
        || (entry->expire > now && fsync(fd) < 0)
    ) {
        fatal(poolfile);
    }
}

static ipaddr_t findpool(u8_t *client, size_t len, ipaddr_t ifip)
{
    /* Look for a client ID in the dynamic address pool within the same network
     * as 'ifip'.  Select an unused one for a new client if necessary.  Return
     * 0 if nothing is available, otherwise the IP address we can offer.
     */
    int fd, found;
    pool_t entry, oldest;
    dhcp_t dhcp;
    u8_t *pmask;
    ipaddr_t mask;

    /* Any information available on the network the client is at? */
    if (!makedhcp(&dhcp, nil, 0, nil, 0, ifip, ifip, nil)) return 0;

    if ((fd= openpool(O_RDWR)) < 0) return 0;

    (void) gettag(&dhcp, DHCP_TAG_NETMASK, &pmask, nil);
    memcpy(&mask, pmask, sizeof(mask));

    oldest.expire= NEVER;
    while ((found= readpool(fd, &entry))) {
        /* Deleted entry? */
        if (entry.ip == 0) continue;

        /* Correct network? */
        if (((entry.ip ^ ifip) & mask) != 0) continue;

        /* Client present? */
        if (entry.len == len && memcmp(entry.clid, client, len) == 0) break;

        /* Oldest candidate for a new lease? */
        entry.expire= ntohl(entry.expire);
        if (entry.expire < oldest.expire) oldest= entry;
    }
    close(fd);

    if (found) return entry.ip;
    if (oldest.expire <= now) return oldest.ip;
    return 0;
}

static int commitpool(ipaddr_t ip, u8_t *client, size_t len, time_t expire)
{
    /* Commit a new binding to stable storage, return true on success. */
    int fd;
    pool_t entry;

    if ((fd= openpool(O_RDWR)) < 0) return 0;

    do {
        if (!readpool(fd, &entry)) {
            close(fd);
            return 0;
        }
    } while (entry.ip != ip);

    entry.expire= htonl(expire);
    entry.len= len;
    memcpy(entry.clid, client, len);
    if (lseek(fd, -(off_t)sizeof(entry), SEEK_CUR) == -1) fatal(poolfile);
    writepool(fd, &entry);
    close(fd);
    return 1;
}

static void updatepool(int add, const char *name)
{
    /* Add a new IP address to the dynamic pool. */
    ipaddr_t ip;
    int fd, i;
    pool_t entry;
    struct hostent *he;
    off_t off, off0;

    if ((he= gethostbyname(name)) == nil || he->h_addrtype != AF_INET) {
        fprintf(stderr, "%s: %s: Unknown host\n", program, name);
        exit(1);
    }
    for (i= 0; he->h_addr_list[i] != nil; i++) {}
    if (i != 1) {
        fprintf(stderr, "%s: %s has %d addresses\n", program, name, i);
        exit(1);
    }
    memcpy(&ip, he->h_addr_list[0], sizeof(ip));

    if ((fd= openpool(O_RDWR|O_CREAT)) < 0) fatal(poolfile);

    off= 0;
    off0= -1;
    while (readpool(fd, &entry)) {
        if (add) {
            if (entry.ip == ip) {
                fprintf(stderr, "%s: %s: %s is already present\n",
                    program, poolfile, name);
                exit(1);
            }
            if (entry.ip == 0 && off0 == -1) off0= off;
        } else {
            if (entry.ip == ip) {
                memset(&entry, 0, sizeof(entry));
                entry.magic= POOL_MAGIC;
                entry.ip= 0;
                if (lseek(fd, off, SEEK_SET) == -1) fatal(poolfile);
                writepool(fd, &entry);
            }
        }
        off+= sizeof(entry);
    }

    if (add) {
        if (off0 != -1 && lseek(fd, off0, SEEK_SET) == -1) fatal(poolfile);
        memset(&entry, 0, sizeof(entry));
        entry.magic= POOL_MAGIC;
        entry.ip= ip;
        writepool(fd, &entry);
    }
    close(fd);
}

static void cachedhcp(int n, dhcp_t *dp)
{
    /* Store a DHCP packet in a cache where those who care can find it. */
    static int inited;
    FILE *fp;
    int fd;
    int mode;

    if (test > 0) return;

    if (!inited) {
        /* First time, clear store and also save my pid. */
        if ((fp= fopen(PATH_DHCPPID, "w")) != nil) {
            if (fprintf(fp, "%d\n", getpid()) == EOF || fclose(fp) == EOF) {
                fatal(PATH_DHCPPID);
            }
        }
        inited= 1;
        mode= O_WRONLY | O_CREAT | O_TRUNC;
    } else {
        mode= O_WRONLY;
    }

    dp->xid= htonl(now);        /* To tell how old this data is. */

    if ((fd= open(cachefile, mode, 0666)) < 0
        || lseek(fd, (off_t) n * sizeof(*dp), SEEK_SET) == -1
        || write(fd, dp, sizeof(*dp)) < 0
        || close(fd) < 0
    ) {
        if (errno != ENOENT) fatal(cachefile);
    }
}

static void printdata(void)
{
    /* Show the contents of the cache and the dynamic pool. */
    int fd;
    dhcp_t d;
    ssize_t r;
    int i;
    pool_t entry;
    unsigned long expire;
    char delta[3*sizeof(u32_t)];

    initdhcpconf();

    if ((fd= open(cachefile, O_RDONLY)) < 0) fatal(cachefile);
    i= 0;
    while ((r= read(fd, &d, sizeof(d))) == sizeof(d)) {
        if (d.yiaddr != 0) {
            printf("DHCP data for network %d:\n", i);
            printdhcp(&d);
        }
        i++;
    }
    if (r < 0) fatal(cachefile);
    close(fd);

    if ((fd= openpool(O_RDONLY)) >= 0) {
        printf("Dynamic address pool since %ld:\n", (long) now);
        while (readpool(fd, &entry)) {
            if (entry.ip == 0) continue;
            expire= ntohl(entry.expire);
            if (expire == 0) {
                strcpy(delta, "unused");
            } else
            if (expire == 0xFFFFFFFFUL) {
                strcpy(delta, "infinite");
            } else
            if (expire < now) {
                sprintf(delta, "-%lu", now - expire);
            } else {
                sprintf(delta, "+%lu", expire - now);
            }
            printf("\t%-15s %8s  ", inet_ntoa(entry.ip), delta);
            for (i= 0; i < entry.len; i++) {
                printf("%02X", entry.clid[i]);
            }
            fputc('\n', stdout);
        }
        close(fd);
    }
}

static udpport_t portbyname(const char *name)
{
    struct servent *se;

    if ((se= getservbyname(name, "udp")) == nil) {
        fprintf(stderr, "%s: Unknown port \"%s\"\n", program, name);
        exit(1);
    }
    return se->s_port;
}

static int send(network_t *np, void *data, size_t len)
{
    /* Send out a packet using a filedescriptor that is probably in async mode,
     * so first dup() a sync version, then write.  Return true on success.
     */
    int fd;
    ssize_t r;

    if ((fd= dup(np->fdp->fd)) < 0) fatal("Can't dup()");
    if ((r= write(fd, data, len)) < 0) {
        report(np->fdp->device);
        sleep(10);
    }
    close(fd);
    return r >= 0;
}

static size_t servdhcp(network_t *np, buf_t *bp, size_t dlen)
{
    buf_t *abp= nil;
    ipaddr_t cip, ifip;
    u8_t defclid[1+sizeof(bp->dhcp->chaddr)];
    u8_t *pdata, *client, *class, *server, *reqip, *lease;
    u32_t expire;
    size_t len, cilen, calen;
    int type, dyn;
    u8_t atype;
    static char NAKMESS[] = "IP address requested isn't yours";

    if (test > 0) return 0;

    /* The IP address of the interface close to the client. */
    ifip= bp->dhcp->giaddr != 0 ? bp->dhcp->giaddr : np->ip;

    /* All kinds of DHCP tags. */
    if (gettag(bp->dhcp, DHCP_TAG_TYPE, &pdata, nil)) {
        type= *pdata;
    } else {
        type= -1;               /* BOOTP? */
    }

    if (!gettag(bp->dhcp, DHCP_TAG_CLIENTID, &client, &cilen)) {
        defclid[0]= bp->dhcp->htype;
        memcpy(defclid+1, bp->dhcp->chaddr, bp->dhcp->hlen);
        client= defclid;
        cilen= 1+bp->dhcp->hlen;
    }

    if (!gettag(bp->dhcp, DHCP_TAG_CLASSID, &class, &calen)) {
        calen= 0;
    }

    if (!gettag(bp->dhcp, DHCP_TAG_SERVERID, &server, nil)) {
        server= B(&np->ip);
    }

    if (!gettag(bp->dhcp, DHCP_TAG_REQIP, &reqip, nil)) {
        reqip= nil;
    }

    /* I'm a server?  Then see if I know this client. */
    if ((np->flags & NF_SERVING)
        && bp->dhcp->op == DHCP_BOOTREQUEST
        && between(1, bp->dhcp->hlen, sizeof(bp->dhcp->chaddr))
        && (server == nil || memcmp(server, &np->ip, sizeof(np->ip)) == 0)
    ) {
        get_buf(&abp);

        /* Is the client in my tables? */
        (void) makedhcp(abp->dhcp, class, calen, client, cilen, 0, ifip, nil);
        cip= abp->dhcp->yiaddr;

        dyn= 0;
        /* If not, do we have a dynamic address? */
        if (cip == 0 && (cip= findpool(client, cilen, ifip)) != 0) dyn= 1;

        if (type == DHCP_INFORM) {
            /* The client already has an address, it just wants information.
             * We only answer if we could answer a normal request (cip != 0),
             * unless configured to answer anyone.
             */
            if (cip != 0 || (np->flags & NF_INFORM)) cip= bp->dhcp->ciaddr;
        }

        if (cip == 0 || !makedhcp(abp->dhcp, class, calen,
                                        client, cilen, cip, ifip, nil)) {
            put_buf(&abp);
        }

        if (abp != nil) {
            if (gettag(abp->dhcp, DHCP_TAG_LEASE, &lease, nil)) {
                memcpy(&expire, lease, sizeof(expire));
                expire= now + ntohl(expire);
                if (expire < now) expire= 0xFFFFFFFFUL;
            } else {
                if (dyn) {
                    /* A dynamic address must have a lease. */
                    fprintf(stderr, "%s: No lease set for address %s\n",
                        program, inet_ntoa(cip));
                    exit(1);
                }
                lease= nil;
                expire= 0xFFFFFFFFUL;
            }

            /* What does our client want, and what do we say? */
            switch (type) {
            case DHCP_DISCOVER:
                atype= DHCP_OFFER;

                /* Assign this address for a short moment. */
                if (dyn && !commitpool(cip, client, cilen, now + DELTA_FAST)) {
                    put_buf(&abp);
                }
                break;

            case -1:/* BOOTP */
            case DHCP_REQUEST:
            case DHCP_INFORM:
                atype= DHCP_ACK;
                /* The address wanted must be the address we offer. */
                if ((reqip != nil && memcmp(reqip, &cip, sizeof(cip)) != 0)
                    || (bp->dhcp->ciaddr != 0 && bp->dhcp->ciaddr != cip)
                ) {
                    atype= DHCP_NAK;
                } else
                if (dyn && type == DHCP_REQUEST) {
                    /* Assign this address for the duration of the lease. */
                    if (!commitpool(cip, client, cilen, expire)) put_buf(&abp);
                }
                break;

            case DHCP_DECLINE:
                /* Our client doesn't want the offered address! */
                if (dyn
                    && reqip != nil
                    && memcmp(reqip, &cip, sizeof(cip)) == 0
                ) {
                    int i;

                    fprintf(stderr, "%s: ", program);
                    for (i= 0; i < cilen; i++) {
                        fprintf(stderr, "%02X", client[i]);
                    }
                    fprintf(stderr, " declines %s", inet_ntoa(cip));
                    if (gettag(bp->dhcp, DHCP_TAG_MESSAGE, &pdata, &len)) {
                        fprintf(stderr, " saying: \"%.*s\"", (int)len, pdata);
                    }
                    fputc('\n', stderr);

                    /* Disable address for the duration of the lease. */
                    (void) commitpool(cip, nil, 0, expire);
                }
                put_buf(&abp);
                break;

            case DHCP_RELEASE:
                /* Our client is nice enough to return its address. */
                if (dyn) (void) commitpool(cip, client, cilen, now);
                put_buf(&abp);
                break;

            default:    /* Anything else is ignored. */
                put_buf(&abp);
            }
        }

        if (abp != nil) {
            /* Finish the return packet. */
            abp->dhcp->htype= bp->dhcp->htype;
            abp->dhcp->hlen= bp->dhcp->hlen;
            abp->dhcp->hops= 0;
            abp->dhcp->xid= bp->dhcp->xid;
            abp->dhcp->secs= 0;
            abp->dhcp->flags= bp->dhcp->flags;
            abp->dhcp->ciaddr= 0;
            abp->dhcp->yiaddr= atype == DHCP_NAK ? 0 : cip;
            if (atype == DHCP_NAK) abp->dhcp->siaddr= 0;
            abp->dhcp->giaddr= bp->dhcp->giaddr;
            memcpy(abp->dhcp->chaddr,bp->dhcp->chaddr,sizeof(bp->dhcp->chaddr));

            settag(abp->dhcp, DHCP_TAG_SERVERID, &np->ip, sizeof(np->ip));

            if (lease == nil) {
                /* No lease specified?  Then give an infinite lease. */
                settag(abp->dhcp, DHCP_TAG_LEASE, &expire, sizeof(expire));
            }

            if (type == DHCP_INFORM) {
                /* Oops, this one has a fixed address, so no lease business. */
                abp->dhcp->yiaddr= 0;
                settag(abp->dhcp, DHCP_TAG_LEASE, nil, 0);
                settag(abp->dhcp, DHCP_TAG_RENEWAL, nil, 0);
                settag(abp->dhcp, DHCP_TAG_REBINDING, nil, 0);
            }

            if (atype == DHCP_NAK) {
                /* A NAK doesn't need much. */
                memset(abp->dhcp->sname, 0, sizeof(abp->dhcp->sname));
                memset(abp->dhcp->file, 0, sizeof(abp->dhcp->file));
                memset(abp->dhcp->options, 255, sizeof(abp->dhcp->options));
                settag(abp->dhcp, DHCP_TAG_MESSAGE, NAKMESS, sizeof(NAKMESS));
            }

            settag(abp->dhcp, DHCP_TAG_TYPE, &atype, sizeof(atype));

            /* Figure out where to send this to. */
            abp->udpio->uih_src_addr= np->ip;
            abp->udpio->uih_src_port= port_server;
            if (bp->dhcp->giaddr != 0) {
                abp->udpio->uih_dst_addr= bp->dhcp->giaddr;
                abp->udpio->uih_dst_port= port_server;
            } else
            if (bp->dhcp->flags & DHCP_FLAGS_BCAST) {
                abp->udpio->uih_dst_addr= BCAST_IP;
                abp->udpio->uih_dst_port= port_client;
            } else
            if (bp->udpio->uih_src_addr != 0
                && bp->udpio->uih_dst_addr == np->ip
            ) {
                abp->udpio->uih_dst_addr= bp->udpio->uih_src_addr;
                abp->udpio->uih_dst_port= port_client;
            } else {
                abp->udpio->uih_dst_addr= BCAST_IP;
                abp->udpio->uih_dst_port= port_client;
            }
            abp->udpio->uih_ip_opt_len= 0;
            abp->udpio->uih_data_len= sizeof(dhcp_t);

            /* Copy the packet to the input buffer, and return the new size. */
            memcpy(bp->buf, abp->buf, sizeof(bp->buf));
            put_buf(&abp);
            return sizeof(udp_io_hdr_t) + sizeof(dhcp_t);
        }
    }

    /* I'm a relay?  If it is a not already a relayed request then relay. */
    if ((np->flags & NF_RELAYING)
        && bp->dhcp->op == DHCP_BOOTREQUEST
        && bp->dhcp->giaddr == 0
    ) {
        bp->dhcp->giaddr= np->ip;
        bp->udpio->uih_src_addr= np->ip;
        bp->udpio->uih_src_port= port_server;
        bp->udpio->uih_dst_addr= np->server;
        bp->udpio->uih_dst_port= port_server;
        return dlen;
    }

    /* I'm a relay?  If the server sends a reply to me then relay back. */
    if ((np->flags & NF_RELAYING)
        && bp->dhcp->op == DHCP_BOOTREPLY
        && bp->dhcp->giaddr == np->ip
    ) {
        bp->dhcp->giaddr= 0;
        bp->udpio->uih_src_addr= np->ip;
        bp->udpio->uih_src_port= port_server;
        bp->udpio->uih_dst_addr= BCAST_IP;
        bp->udpio->uih_dst_port= port_client;
        return dlen;
    }

    /* Don't know what to do otherwise, so doing nothing seems wise. */
    return 0;
}

static void onsig(int sig)
{
    switch (sig) {
    case SIGUSR1:       debug++;        break;
    case SIGUSR2:       debug= 0;       break;
    }
}

static void usage(void)
{
    fprintf(stderr,
"Usage: %s [-qar] [-t[L]] [-d[L]] [-f config] [-c cache] [-p pool] [host ...]\n",
        program);
    exit(1);
}

int main(int argc, char **argv)
{
    int i;
    network_t *np;
    struct sigaction sa;
    ssize_t r= -1;
    buf_t *bp= nil;
    static struct timeval eventtv;

    program= argv[0];
    start= now= time(nil);

    debug= 0;
    i= 1;
    while (i < argc && argv[i][0] == '-') {
        char *opt= argv[i++]+1;

        if (opt[0] == '-' && opt[1] == 0) break;        /* -- */

        while (*opt != 0) switch (*opt++) {
        case 'f':
            if (*opt == 0) {
                if (i == argc) usage();
                opt= argv[i++];
            }
            configfile= opt;
            opt= "";
            break;
        case 'c':
            if (*opt == 0) {
                if (i == argc) usage();
                opt= argv[i++];
            }
            cachefile= opt;
            opt= "";
            break;
        case 'p':
            if (*opt == 0) {
                if (i == argc) usage();
                opt= argv[i++];
            }
            poolfile= opt;
            opt= "";
            break;
        case 't':
            test= 1;
            if (between('0', *opt, '9')) test= strtoul(opt, &opt, 10);
            break;
        case 'd':
            debug= 1;
            if (between('0', *opt, '9')) debug= strtoul(opt, &opt, 10);
            break;
        case 'q':
            qflag= 1;
            break;
        case 'a':
            aflag= 1;
            break;
        case 'r':
            rflag= 1;
            break;
        default:
            usage();
        }
    }
    if (aflag + rflag + qflag > 1) usage();

    if (aflag || rflag) {
        /* Add or remove addresses from the dynamic pool. */
        while (i < argc) updatepool(aflag, argv[i++]);
        exit(0);
    }

    if (i != argc) usage();

    if (qflag) {
        /* Only show the contents of the cache and dynamic pool to the user. */
        printdata();
        exit(0);
    }

    /* BOOTP ports. */
    port_server= portbyname("bootps");
    port_client= portbyname("bootpc");

    sa.sa_handler= onsig;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags= 0;
    sigaction(SIGUSR1, &sa, nil);
    sigaction(SIGUSR2, &sa, nil);

    /* Initial configuration. */
    for (i= 0; i < N_NETS; i++) {
        int fd;
        ipaddr_t ip, mask;

        /* Is there something there? */
        if ((fd= open(ipdev(i), O_RDWR|O_NONBLOCK)) < 0) {
            if (errno != ENOENT && errno != ENODEV && errno != ENXIO) {
                fatal(ipdev(i));
            }
            continue;
        }
        close(fd);

        network[n_nets++]= np= newnetwork();
        np->n= i;

        /* Ethernet? */
        if (opendev(np, FT_ETHERNET, 1)) {
            np->type= B(&np->eth)[0] != 'Z' ? NT_ETHERNET : NT_SINK;
            if (debug >= 1) {
                printf("%s: Ethernet address is %s%s\n",
                    np->fdp->device, ether_ntoa(&np->eth),
                    np->type == NT_SINK ? " (sink)" : "");
            }
            closedev(np, FT_ETHERNET);
        }

        /* Only true Ethernets worry about DHCP. */
        if (np->type != NT_ETHERNET) np->renew= np->rebind= np->lease= NEVER;
    }

    /* Try to find my interfaces in the DHCP table. */
    for (i= 0; i < n_nets; i++) {
        ipaddr_t cip;
        u8_t clid[1+DHCP_HLEN_ETH];
        size_t cilen;

        np= network[i];
        if (np->flags & NF_BOUND) continue;

        if (np->type == NT_IP) {
            cilen= 0;
        } else {
            ether2clid(clid, &np->eth);
            cilen= 1+DHCP_HLEN_ETH;
        }

        /* Try to find an Ethernet address, or the IP address of an already
         * configured network.  If we have data we get an IP address back.
         */
        get_buf(&bp);
        (void) makedhcp(bp->dhcp, (u8_t *) "Minix", 5,
                                        clid, cilen, np->ip, 0, np);
        cip= bp->dhcp->yiaddr;

        /* Gather information on the interface. */
        if (cip != 0
            && makedhcp(bp->dhcp, (u8_t *) "Minix", 5,
                                        clid, cilen, cip, cip, np)
            && test < 2
        ) {
            u8_t *pdata;
            u16_t mtu;

            cachedhcp(np->n, bp->dhcp);
            np->ip= cip;
            (void) gettag(bp->dhcp, DHCP_TAG_NETMASK, &pdata, nil);
            memcpy(&np->mask, pdata, sizeof(np->mask));
            if (gettag(bp->dhcp, DHCP_TAG_GATEWAY, &pdata, nil)) {
                memcpy(&np->gateway, pdata, sizeof(np->gateway));
            } else {
                np->gateway= 0;
            }
            if (gettag(bp->dhcp, DHCP_TAG_IPMTU, &pdata, nil)) {
                memcpy(&mtu, pdata, sizeof(mtu));
                mtu= ntohs(mtu);
            } else {
                mtu= 0;
            }
            set_ipconf(ipdev(np->n), np->ip, np->mask, mtu);
            if (debug >= 1) {
                printf("%s: IP address is %s\n",
                    ipdev(np->n), cidr_ntoa(np->ip, np->mask));
            }
            np->flags |= NF_BOUND;
            np->renew= np->rebind= np->lease= NEVER;
            np->sol_ct= N_SOLICITS;
            np->solicit= 0;

            /* Other (previous) interfaces may have been defined. */
            i= 0;
        }
        put_buf(&bp);
    }

    for (;;) {
        now= time(nil);
        event= NEVER;

        /* Is it time to request/renew a lease? */
        for (i= 0; i < n_nets; i++) {
            np= network[i];

            if (np->renew <= now) {
                u8_t type;
                static u8_t taglist[] = {
                    DHCP_TAG_NETMASK, DHCP_TAG_GATEWAY, DHCP_TAG_DNS,
                        DHCP_TAG_HOSTNAME
                };
                u8_t ethclid[1+DHCP_HLEN_ETH];

                /* We may have lost our binding or even our lease. */
                if (np->rebind <= now) np->server= BCAST_IP;

                if (np->lease <= now) {
                    if (np->flags & NF_BOUND) closedev(np, FT_ALL);

                    if ((np->flags & (NF_BOUND | NF_POSSESSIVE)) == NF_BOUND) {
                        set_ipconf(ipdev(np->n), np->ip= 0, np->mask= 0, 0);
                        if (debug >= 1) {
                            printf("%s: Interface disabled (lease expired)\n",
                                ipdev(np->n));
                        }
                    }
                    np->flags &= ~NF_BOUND;
                }

                /* See if we can open the network we need to send on. */
                if (!(np->flags & NF_BOUND)) {
                    if (!opendev(np, FT_ETHERNET, 1)) continue;
                } else {
                    if (!opendev(np, FT_BOOTPC, 1)) continue;
                }

                if (!(np->flags & NF_NEGOTIATING)) {
                    /* We need to start querying a DHCP server. */
                    np->start= now;
                    np->delta= DELTA_FIRST;
                    np->flags |= NF_NEGOTIATING;
                }

                /* Fill in a DHCP query packet. */
                get_buf(&bp);
                dhcp_init(bp->dhcp);
                bp->dhcp->op= DHCP_BOOTREQUEST;
                bp->dhcp->htype= DHCP_HTYPE_ETH;
                bp->dhcp->hlen= DHCP_HLEN_ETH;
                bp->dhcp->xid= XID(np);
                bp->dhcp->secs= htons(now - np->start > 0xFFFF
                                        ? 0xFFFF : now - np->start);
                memcpy(bp->dhcp->chaddr, &np->eth, sizeof(np->eth));

                if (np->lease <= now) {
                    /* First time, or my old server is unresponsive. */
                    type= DHCP_DISCOVER;
                } else {
                    /* Request an offered address or renew an address. */
                    type= DHCP_REQUEST;
                    if (np->flags & NF_BOUND) {
                        /* A renewal, I claim my current address. */
                        bp->dhcp->ciaddr= np->ip;
                    } else {
                        /* Nicely ask for the address just offered. */
                        settag(bp->dhcp, DHCP_TAG_REQIP, &np->ip,
                                                        sizeof(np->ip));
                        settag(bp->dhcp, DHCP_TAG_SERVERID, &np->server,
                                                        sizeof(np->server));
                    }
                }
                settag(bp->dhcp, DHCP_TAG_TYPE, &type, 1);

                /* My client ID.  Simply use the default. */
                ether2clid(ethclid, &np->eth);
                settag(bp->dhcp, DHCP_TAG_CLIENTID, ethclid, sizeof(ethclid));

                /* The Class ID may serve to recognize Minix hosts. */
                settag(bp->dhcp, DHCP_TAG_CLASSID, "Minix", 5);

                /* The few tags that Minix can make good use of. */
                settag(bp->dhcp, DHCP_TAG_REQPAR, taglist, sizeof(taglist));

                /* Some weird sites use a hostname, not a client ID. */
                if (np->hostname != nil) {
                    settag(bp->dhcp, DHCP_TAG_HOSTNAME,
                                        np->hostname, strlen(np->hostname));
                }

                bp->udpio->uih_src_addr= np->ip;
                bp->udpio->uih_dst_addr= np->server;
                bp->udpio->uih_src_port= port_client;
                bp->udpio->uih_dst_port= port_server;
                bp->udpio->uih_ip_opt_len= 0;
                bp->udpio->uih_data_len= sizeof(dhcp_t);

                if (!(np->flags & NF_BOUND)) {
                    /* Rebind over Ethernet. */
                    udp2ether(bp, np);
                    if (send(np, bp->eth, sizeof(eth_hdr_t) + sizeof(ip_hdr_t)
                                        + sizeof(udp_hdr_t) + sizeof(dhcp_t))) {
                        if (debug >= 1) {
                            printf("%s: Broadcast DHCP %s\n",
                                np->fdp->device, dhcptypename(type));
                            if (debug >= 2) printdhcp(bp->dhcp);
                        }
                    }
                } else {
                    /* Renew over UDP. */
                    if (send(np, bp->udpio, sizeof(udp_io_hdr_t)
                                                        + sizeof(dhcp_t))) {
                        if (debug >= 1) {
                            printf("%s: Sent DHCP %s to %s\n",
                                np->fdp->device,
                                dhcptypename(type),
                                inet_ntoa(np->server));
                            if (debug >= 2) printdhcp(bp->dhcp);
                        }
                    }
                }
                put_buf(&bp);

                /* When to continue querying a DHCP server? */
                if (np->flags & NF_BOUND) {
                    /* Still bound, keep halving time till next event. */
                    time_t e, d;

                    e= now < np->rebind ? np->rebind : np->lease;
                    d= (e - now) / 2;
                    if (d < DELTA_SLOW) d= DELTA_SLOW;
                    np->renew= now + d;
                    if (np->renew > e) np->renew= e;
                } else {
                    /* Not bound, be desparate. */
                    np->renew= now + np->delta;
                    if ((np->delta *= 2) > DELTA_FAST) np->delta= DELTA_FAST;
                }
            }
            if (np->renew < event) event= np->renew;
        }

        /* Read DHCP responses. */
        for (i= 0; i < n_nets; i++) {
            np= network[i];
            if (!(np->flags & NF_NEGOTIATING)) continue;

            if (!(np->flags & NF_BOUND)) {
                if (!opendev(np, FT_ETHERNET, 0)) continue;
                get_buf(&np->fdp->bp);
                r= asyn_read(&asyn, np->fdp->fd, np->fdp->bp->eth,
                                                        BUF_ETH_SIZE);
            } else {
                if (!opendev(np, FT_BOOTPC, 0)) continue;
                get_buf(&np->fdp->bp);
                r= asyn_read(&asyn, np->fdp->fd, np->fdp->bp->udpio,
                                                        BUF_UDP_SIZE);
            }
            if (r != -1) break;
            if (errno != ASYN_INPROGRESS && errno != EPACKSIZE) {
                report(np->fdp->device);
                sleep(10);
            }
        }

        /* Is there a response? */
        if (i < n_nets) {
            give_buf(&bp, &np->fdp->bp);
            if (((!(np->flags & NF_BOUND)
                    && r >= (sizeof(eth_hdr_t) + sizeof(ip_hdr_t)
                                + sizeof(udp_hdr_t) + offsetof(dhcp_t, options))
                    && ether2udp(bp)
                    && bp->udpio->uih_dst_port == port_client)
                  ||
                  ((np->flags & NF_BOUND)
                    && r >= sizeof(udp_io_hdr_t) + offsetof(dhcp_t, options)))
                && bp->dhcp->op == DHCP_BOOTREPLY
                && bp->dhcp->htype == DHCP_HTYPE_ETH
                && bp->dhcp->hlen == DHCP_HLEN_ETH
                && bp->dhcp->xid == XID(np)
                && memcmp(bp->dhcp->chaddr, &np->eth, sizeof(np->eth)) == 0
            ) {
                /* Pfew!  We got a DHCP reply! */
                u8_t *pdata;
                size_t len;
                int type;
                ipaddr_t mask, gateway, relay, server;
                u16_t mtu;
                u32_t lease, renew, rebind, t;

                relay= bp->udpio->uih_src_addr;
                if (gettag(bp->dhcp, DHCP_TAG_SERVERID, &pdata, nil)) {
                    memcpy(&server, pdata, sizeof(server));
                } else {
                    server= relay;
                }

                if (gettag(bp->dhcp, DHCP_TAG_TYPE, &pdata, nil)) {
                    type= pdata[0];
                } else {
                    type= DHCP_ACK;     /* BOOTP? */
                }

                if (debug >= 1) {
                    printf("%s: Got a DHCP %s from %s",
                        np->fdp->device, dhcptypename(type), inet_ntoa(server));
                    printf(relay != server ? " through %s\n" : "\n",
                        inet_ntoa(relay));
                    if (debug >= 2) printdhcp(bp->dhcp);
                }

                if (gettag(bp->dhcp, DHCP_TAG_NETMASK, &pdata, nil)) {
                    memcpy(&mask, pdata, sizeof(mask));
                } else {
                    mask= defaultmask(bp->dhcp->ciaddr);
                }

                if (gettag(bp->dhcp, DHCP_TAG_IPMTU, &pdata, nil)) {
                    memcpy(&mtu, pdata, sizeof(mtu));
                    mtu= ntohs(mtu);
                } else {
                    mtu= 0;
                }

                if (gettag(bp->dhcp, DHCP_TAG_GATEWAY, &pdata, nil)) {
                    memcpy(&gateway, pdata, sizeof(gateway));
                } else {
                    gateway= 0;
                }

                lease= NEVER;
                if (gettag(bp->dhcp, DHCP_TAG_LEASE, &pdata, nil)) {
                    memcpy(&lease, pdata, sizeof(lease));
                    lease= ntohl(lease);
                }

                rebind= lease - lease / 8;
                if (gettag(bp->dhcp, DHCP_TAG_REBINDING, &pdata, nil)) {
                    memcpy(&t, pdata, sizeof(t));
                    t= ntohl(t);
                    if (t < rebind) rebind= t;
                }

                renew= lease / 2;
                if (gettag(bp->dhcp, DHCP_TAG_RENEWAL, &pdata, nil)) {
                    memcpy(&t, pdata, sizeof(t));
                    t= ntohl(t);
                    if (t < renew) renew= t;
                }

                if (type == DHCP_OFFER && np->rebind <= np->renew) {
                    /* It's an offer for an address and we haven't taken one
                     * yet.  It's all the same to us, so take this one.
                     */
                    np->ip= bp->dhcp->yiaddr;
                    np->mask= mask;
                    np->server= server;
                    np->gateway= gateway;
                    np->delta= DELTA_FIRST;
                    np->renew= now;
                    np->rebind= np->lease= now + DELTA_FAST;

                    /* Send out an ARP request to see if the offered address
                     * is in use already.
                     */
                    make_arp(bp, np);
                    if (send(np, bp->eth, sizeof(arp46_t))) {
                        if (debug >= 2) {
                            printf("Sent ARP for %s\n", inet_ntoa(np->ip));
                        }
                    }
                    np->flags &= ~NF_CONFLICT;
                }

                if (type == DHCP_ACK && !(np->flags & NF_CONFLICT)) {
                    /* An acknowledgment.  The address is all mine. */
                    cachedhcp(np->n, bp->dhcp);
                    np->ip= bp->dhcp->yiaddr;
                    np->mask= mask;
                    np->server= server;
                    set_ipconf(ipdev(np->n), np->ip, np->mask, mtu);
                    if (debug >= 1) {
                        printf("%s: Address set to %s\n",
                            ipdev(np->n), cidr_ntoa(np->ip, np->mask));
                    }
                    if (lease >= NEVER - now) {
                        /* The lease is infinite! */
                        np->renew= np->rebind= np->lease= NEVER;
                    } else {
                        np->lease= now + lease;
                        np->renew= now + renew;
                        np->rebind= now + rebind;
                    }
                    if (test >= 3) {
                        np->renew= now + 60;
                        np->rebind= test >= 4 ? np->renew : np->renew + 60;
                        np->lease= test >= 5 ? np->rebind : np->rebind + 60;
                    }
                    if (!(np->flags & NF_IRDP)) {
                        np->sol_ct= (np->flags & NF_BOUND) ? 1 : N_SOLICITS;
                        np->solicit= 0;
                    }
                    np->flags &= ~NF_NEGOTIATING;
                    np->flags |= NF_BOUND;
                    closedev(np, FT_ETHERNET);
                    closedev(np, FT_BOOTPC);
                }

                if (type == DHCP_ACK && (np->flags & NF_CONFLICT)) {
                    /* Alas there is a conflict.  Decline to use the address. */
                    u8_t ethclid[1+DHCP_HLEN_ETH];
                    static char USED[]= "Address in use by 00:00:00:00:00:00";

                    type= DHCP_DECLINE;
                    dhcp_init(bp->dhcp);
                    bp->dhcp->op= DHCP_BOOTREQUEST;
                    bp->dhcp->htype= DHCP_HTYPE_ETH;
                    bp->dhcp->hlen= DHCP_HLEN_ETH;
                    bp->dhcp->xid= XID(np);
                    bp->dhcp->secs= 0;
                    memcpy(bp->dhcp->chaddr, &np->eth, sizeof(np->eth));
                    settag(bp->dhcp, DHCP_TAG_REQIP, &np->ip, sizeof(np->ip));
                    settag(bp->dhcp, DHCP_TAG_TYPE, &type, 1);
                    ether2clid(ethclid, &np->eth);
                    settag(bp->dhcp, DHCP_TAG_CLIENTID,ethclid,sizeof(ethclid));
                    strcpy(USED+18, ether_ntoa(&np->conflict));
                    settag(bp->dhcp, DHCP_TAG_MESSAGE, USED, strlen(USED));

                    bp->udpio->uih_src_port= port_client;
                    bp->udpio->uih_dst_port= port_server;
                    bp->udpio->uih_ip_opt_len= 0;
                    bp->udpio->uih_data_len= sizeof(dhcp_t);
                    udp2ether(bp, np);

                    if (send(np, bp->eth, sizeof(eth_hdr_t) + sizeof(ip_hdr_t)
                                        + sizeof(udp_hdr_t) + sizeof(dhcp_t))) {
                        if (debug >= 1) {
                            printf("%s: Broadcast DHCP %s\n",
                                np->fdp->device, dhcptypename(type));
                            if (debug >= 2) printdhcp(bp->dhcp);
                        }
                    }
                    
                    np->renew= np->rebind= np->lease= now + DELTA_FAST;
                    np->delta= DELTA_FIRST;
                }

                if (type == DHCP_NAK) {
                    /* Oops, a DHCP server doesn't like me, start over! */
                    np->renew= np->rebind= np->lease= now + DELTA_FAST;
                    np->delta= DELTA_FIRST;

                    fprintf(stderr, "%s: Got a NAK from %s",
                        program, inet_ntoa(server));
                    if (relay != server) {
                        fprintf(stderr, " through %s", inet_ntoa(relay));
                    }
                    if (gettag(bp->dhcp, DHCP_TAG_MESSAGE, &pdata, &len)) {
                        fprintf(stderr, " saying: \"%.*s\"", (int)len, pdata);
                    }
                    fputc('\n', stderr);
                }
            } else
            if (!(np->flags & NF_BOUND)
                && np->rebind > now
                && r >= sizeof(arp46_t)
                && is_arp_me(bp, np)
            ) {
                /* Oh no, someone else is using the address offered to me! */
                np->flags |= NF_CONFLICT;

                fprintf(stderr, "%s: %s: %s offered by ",
                        program,
                        np->fdp->device,
                        inet_ntoa(np->ip));
                fprintf(stderr, "%s is already in use by %s\n",
                        inet_ntoa(np->server),
                        ether_ntoa(&np->conflict));
            }
            put_buf(&bp);
            if (np->renew < event) event= np->renew;
        }

        /* Perform router solicitations. */
        for (i= 0; i < n_nets; i++) {
            np= network[i];
            if (!(np->flags & NF_BOUND)) continue;

            if (np->solicit <= now) {
                if (!opendev(np, FT_ICMP, 1)) continue;
                np->solicit= NEVER;

                get_buf(&bp);
                if (np->gateway != 0) {
                    /* No IRDP response seen yet, advertise the router given
                     * by DHCP to my own interface.
                     */
                    icmp_advert(bp, np);
                    if (send(np, bp->ip, sizeof(ip_hdr_t) + 16)) {
                        if (debug >= 2) {
                            printf("%s: Sent advert for %s to self\n",
                                np->fdp->device, inet_ntoa(np->gateway));
                        }
                    }
                    np->solicit= now + DELTA_ADV/2;
                }

                if (np->sol_ct >= 0 && --np->sol_ct >= 0) {
                    /* Send a router solicitation. */
                    icmp_solicit(bp);
                    if (send(np, bp->ip, sizeof(*bp->ip) + 8)) {
                        if (debug >= 2) {
                            printf("%s: Broadcast router solicitation\n",
                                np->fdp->device);
                        }
                    }
                    np->solicit= now + DELTA_SOL;
                } else {
                    /* No response, or not soliciting right now. */
                    closedev(np, FT_ICMP);
                }

                put_buf(&bp);
            }
            if (np->solicit < event) event= np->solicit;
        }

        /* Read router adverts. */
        for (i= 0; i < n_nets; i++) {
            np= network[i];
            if (!(np->flags & NF_BOUND)) continue;
            if (np->sol_ct < 0) continue;

            if (!opendev(np, FT_ICMP, 0)) continue;
            get_buf(&np->fdp->bp);
            r= asyn_read(&asyn, np->fdp->fd, np->fdp->bp->ip, BUF_IP_SIZE);
            if (r != -1) break;
            if (errno != ASYN_INPROGRESS && errno != EPACKSIZE) {
                report(np->fdp->device);
                sleep(10);
            }
        }

        /* Is there an advert? */
        if (i < n_nets && r >= sizeof(ip_hdr_t) + 8) {
            ipaddr_t router;

            give_buf(&bp, &np->fdp->bp);
            if ((router= icmp_is_advert(bp)) != 0) {
                if (debug >= 2) {
                    printf("%s: Router advert received from %s\n",
                        np->fdp->device, inet_ntoa(router));
                }
                np->solicit= NEVER;
                np->sol_ct= -1;
                np->flags |= NF_IRDP;
                closedev(np, FT_ICMP);
            }
            put_buf(&bp);
        }

        /* We start serving if all the interfaces so marked are configured. */
        for (i= 0; i < n_nets; i++) {
            np= network[i];
            if ((np->flags & NF_RELAYING) && (np->flags & NF_BOUND)) {
                if (((np->ip ^ np->server) & np->mask) == 0) {
                    /* Don't relay to a server that is on this same net. */
                    np->flags &= ~NF_RELAYING;
                }
            }
            if (!(np->flags & (NF_SERVING|NF_RELAYING))) continue;
            if (!(np->flags & NF_BOUND)) { serving= 0; break; }
            serving= 1;
        }

        /* Read DHCP requests. */
        for (i= 0; i < n_nets; i++) {
            np= network[i];
            if (!(np->flags & NF_BOUND)) continue;
            if (!(np->flags & (NF_SERVING|NF_RELAYING)) || !serving) continue;

            if (!opendev(np, FT_BOOTPS, 0)) continue;
            get_buf(&np->fdp->bp);
            r= asyn_read(&asyn, np->fdp->fd, np->fdp->bp->udpio, BUF_UDP_SIZE);

            if (r != -1) break;
            if (errno != ASYN_INPROGRESS && errno != EPACKSIZE) {
                report(np->fdp->device);
                sleep(10);
            }
        }

        /* Is there a request? */
        if (i < n_nets
            && r >= sizeof(udp_io_hdr_t) + offsetof(dhcp_t, options)
        ) {
            give_buf(&bp, &np->fdp->bp);

            if (debug >= 1) {
                printf("%s: Got DHCP packet from %s to ",
                    np->fdp->device, inet_ntoa(bp->udpio->uih_src_addr));
                printf("%s\n", inet_ntoa(bp->udpio->uih_dst_addr));
                if (debug >= 2) printdhcp(bp->dhcp);
            }

            /* Can we do something with this DHCP packet? */
            if ((r= servdhcp(np, bp, r)) > 0) {
                /* Yes, we have something to send somewhere. */
                if (send(np, bp->udpio, r)) {
                    if (debug >= 1) {
                        printf("%s: Sent DHCP packet to %s\n",
                            np->fdp->device,
                            inet_ntoa(bp->udpio->uih_dst_addr));
                        if (debug >= 2) printdhcp(bp->dhcp);
                    }
                }
            }
            put_buf(&bp);
        }

        if (debug >= 1) {
            static char *lastbrk;
            extern char _end;

            if (sbrk(0) != lastbrk) {
                lastbrk= sbrk(0);
                printf("Memory use = %lu\n",
                    (unsigned long) (lastbrk - &_end));
            }
            fflush(stdout);
        }

        /* Bail out if not a server, and there is nothing else to do ever. */
        if (!serving && event == NEVER) break;

        /* Wait for something to do. */
        eventtv.tv_sec= event;
        if (asyn_wait(&asyn, 0, event == NEVER ? nil : &eventtv) < 0) {
            if (errno != EINTR) {
                report("asyn_wait()");
                sleep(10);
            }
        }
    }
    if (debug >= 1) printf("Nothing more to do! Bailing out...\n");
    return 0;
}

---