Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <thread.h>
#include <libsec.h>
#include <9p.h>

extern char *Debug;

typedef struct Pingcache Pingcache;
struct Pingcache {
        Pingcache*next;
        long    rtt;
        char    *host;
        long    expire;
};

typedef struct {
        uchar   vihl;           /* Version and header length */
        uchar   tos;            /* Type of service */
        uchar   length[2];      /* packet length */
        uchar   id[2];          /* Identification */
        uchar   frag[2];        /* Fragment information */
        uchar   ttl;            /* Time to live */
        uchar   proto;          /* Protocol */
        uchar   ipcksum[2];     /* Header checksum */
        uchar   src[4];         /* Ip source */
        uchar   dst[4];         /* Ip destination */
        uchar   type;
        uchar   code;
        uchar   cksum[2];
        uchar   icmpid[2];
        uchar   seq[2];
        uchar   data[1];
} Icmp;

enum {                  /* Packet Types */
        EchoReply       = 0,
        Unreachable     = 3,
        SrcQuench       = 4,
        EchoRequest     = 8,
        TimeExceed      = 11,
        Timestamp       = 13,
        TimestampReply  = 14,
        InfoRequest     = 15,
        InfoReply       = 16,

        ICMP_IPSIZE     = 20,
        ICMP_HDRSIZE    = 8,

        Npings          = 8,
        Payload         = 32,

        Cachetime       = 60,
};

static Pingcache *Cache;

/*
 * We ignore the first result as that is probably bigger
 * than expected due to IP sorting out the routing to the host
 */
int
ping(char *host, int timeout)
{
        int rtt, fd, i, seq;
        long now;
        vlong then;
        uchar buf[128];
        Icmp *ip;
        Pingcache *c;

        now = time(nil);
        for(c = Cache; c; c = c->next)
                if(strcmp(c->host, host) == 0 && now < c->expire){
                        if(Debug && strstr(Debug, "dfs") != nil)
                                print("\t\tping host=%s timeout=%d - cache hit\n",
                                        host, timeout);
                        return c->rtt;
                }

        rtt = -1;
        ip = (Icmp*)buf;

        if((fd = dial(netmkaddr(host, "icmp", "1"), 0, 0, 0)) == -1)
                goto fail;

        for(seq = 0; seq < Npings; seq++){
                then = nsec();
                for(i = Payload; i < sizeof buf; i++)
                        buf[i] = i + seq;
                ip->type = EchoRequest;
                ip->code = 0;
                ip->seq[0] = seq;
                ip->seq[1] = seq;
                alarm(timeout);
                if(write(fd, ip, sizeof buf) != sizeof buf ||
                    read(fd, ip, sizeof buf) != sizeof buf)
                        goto fail;
                alarm(0);
                if(ip->type != EchoReply || ip->code != 0 ||
                    ip->seq[0] != seq || ip->seq[1] != seq)
                        goto fail;
                for(i = Payload; i < sizeof buf; i++)
                        if((uchar)buf[i] != (uchar)(i + seq))
                                goto fail;
                rtt = (rtt + nsec() - then) / 2;
        }
fail:
        if(fd != -1)
                close(fd);

        if(Debug && strstr(Debug, "dfs") != nil)
                print("\t\tping host=%s timeout=%d rtt=%d - failed\n",
                        host, timeout, rtt);

        /*
         * failures get cached too
         */
        for(c = Cache; c; c = c->next)
                if(strcmp(c->host, host) == 0)
                        break;
        if(c == nil){
                c = emalloc9p(sizeof(Pingcache));
                c->host = estrdup9p(host);
                c->next = Cache;
                Cache = c;
        }
        c->rtt = rtt;
        c->expire = now+Cachetime;
        return rtt;
}