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root/net/ipv4/ip_options.c

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DEFINITIONS

This source file includes following definitions.
  1. ip_options_build
  2. ip_options_echo
  3. ip_options_fragment
  4. ip_options_compile
  5. ip_options_undo
  6. ip_options_get_alloc
  7. ip_options_get_finish
  8. ip_options_get_from_user
  9. ip_options_get
  10. ip_forward_options
  11. ip_options_rcv_srr

/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              The options processing module for ip.c
 *
 * Authors:     A.N.Kuznetsov
 *
 */

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/types.h>
#include <asm/uaccess.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/cipso_ipv4.h>

/*
 * Write options to IP header, record destination address to
 * source route option, address of outgoing interface
 * (we should already know it, so that this  function is allowed be
 * called only after routing decision) and timestamp,
 * if we originate this datagram.
 *
 * daddr is real destination address, next hop is recorded in IP header.
 * saddr is address of outgoing interface.
 */

void ip_options_build(struct sk_buff * skb, struct ip_options * opt,
                            __be32 daddr, struct rtable *rt, int is_frag)
{
        unsigned char *iph = skb_network_header(skb);

        memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
        memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
        opt = &(IPCB(skb)->opt);

        if (opt->srr)
                memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);

        if (!is_frag) {
                if (opt->rr_needaddr)
                        ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, rt);
                if (opt->ts_needaddr)
                        ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, rt);
                if (opt->ts_needtime) {
                        struct timespec tv;
                        __be32 midtime;
                        getnstimeofday(&tv);
                        midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
                        memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
                }
                return;
        }
        if (opt->rr) {
                memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
                opt->rr = 0;
                opt->rr_needaddr = 0;
        }
        if (opt->ts) {
                memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
                opt->ts = 0;
                opt->ts_needaddr = opt->ts_needtime = 0;
        }
}

/*
 * Provided (sopt, skb) points to received options,
 * build in dopt compiled option set appropriate for answering.
 * i.e. invert SRR option, copy anothers,
 * and grab room in RR/TS options.
 *
 * NOTE: dopt cannot point to skb.
 */

int ip_options_echo(struct ip_options * dopt, struct sk_buff * skb)
{
        struct ip_options *sopt;
        unsigned char *sptr, *dptr;
        int soffset, doffset;
        int     optlen;
        __be32  daddr;

        memset(dopt, 0, sizeof(struct ip_options));

        sopt = &(IPCB(skb)->opt);

        if (sopt->optlen == 0) {
                dopt->optlen = 0;
                return 0;
        }

        sptr = skb_network_header(skb);
        dptr = dopt->__data;

        daddr = skb->rtable->rt_spec_dst;

        if (sopt->rr) {
                optlen  = sptr[sopt->rr+1];
                soffset = sptr[sopt->rr+2];
                dopt->rr = dopt->optlen + sizeof(struct iphdr);
                memcpy(dptr, sptr+sopt->rr, optlen);
                if (sopt->rr_needaddr && soffset <= optlen) {
                        if (soffset + 3 > optlen)
                                return -EINVAL;
                        dptr[2] = soffset + 4;
                        dopt->rr_needaddr = 1;
                }
                dptr += optlen;
                dopt->optlen += optlen;
        }
        if (sopt->ts) {
                optlen = sptr[sopt->ts+1];
                soffset = sptr[sopt->ts+2];
                dopt->ts = dopt->optlen + sizeof(struct iphdr);
                memcpy(dptr, sptr+sopt->ts, optlen);
                if (soffset <= optlen) {
                        if (sopt->ts_needaddr) {
                                if (soffset + 3 > optlen)
                                        return -EINVAL;
                                dopt->ts_needaddr = 1;
                                soffset += 4;
                        }
                        if (sopt->ts_needtime) {
                                if (soffset + 3 > optlen)
                                        return -EINVAL;
                                if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
                                        dopt->ts_needtime = 1;
                                        soffset += 4;
                                } else {
                                        dopt->ts_needtime = 0;

                                        if (soffset + 8 <= optlen) {
                                                __be32 addr;

                                                memcpy(&addr, sptr+soffset-1, 4);
                                                if (inet_addr_type(dev_net(skb->dst->dev), addr) != RTN_LOCAL) {
                                                        dopt->ts_needtime = 1;
                                                        soffset += 8;
                                                }
                                        }
                                }
                        }
                        dptr[2] = soffset;
                }
                dptr += optlen;
                dopt->optlen += optlen;
        }
        if (sopt->srr) {
                unsigned char * start = sptr+sopt->srr;
                __be32 faddr;

                optlen  = start[1];
                soffset = start[2];
                doffset = 0;
                if (soffset > optlen)
                        soffset = optlen + 1;
                soffset -= 4;
                if (soffset > 3) {
                        memcpy(&faddr, &start[soffset-1], 4);
                        for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
                                memcpy(&dptr[doffset-1], &start[soffset-1], 4);
                        /*
                         * RFC1812 requires to fix illegal source routes.
                         */
                        if (memcmp(&ip_hdr(skb)->saddr,
                                   &start[soffset + 3], 4) == 0)
                                doffset -= 4;
                }
                if (doffset > 3) {
                        memcpy(&start[doffset-1], &daddr, 4);
                        dopt->faddr = faddr;
                        dptr[0] = start[0];
                        dptr[1] = doffset+3;
                        dptr[2] = 4;
                        dptr += doffset+3;
                        dopt->srr = dopt->optlen + sizeof(struct iphdr);
                        dopt->optlen += doffset+3;
                        dopt->is_strictroute = sopt->is_strictroute;
                }
        }
        if (sopt->cipso) {
                optlen  = sptr[sopt->cipso+1];
                dopt->cipso = dopt->optlen+sizeof(struct iphdr);
                memcpy(dptr, sptr+sopt->cipso, optlen);
                dptr += optlen;
                dopt->optlen += optlen;
        }
        while (dopt->optlen & 3) {
                *dptr++ = IPOPT_END;
                dopt->optlen++;
        }
        return 0;
}

/*
 *      Options "fragmenting", just fill options not
 *      allowed in fragments with NOOPs.
 *      Simple and stupid 8), but the most efficient way.
 */

void ip_options_fragment(struct sk_buff * skb)
{
        unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
        struct ip_options * opt = &(IPCB(skb)->opt);
        int  l = opt->optlen;
        int  optlen;

        while (l > 0) {
                switch (*optptr) {
                case IPOPT_END:
                        return;
                case IPOPT_NOOP:
                        l--;
                        optptr++;
                        continue;
                }
                optlen = optptr[1];
                if (optlen<2 || optlen>l)
                  return;
                if (!IPOPT_COPIED(*optptr))
                        memset(optptr, IPOPT_NOOP, optlen);
                l -= optlen;
                optptr += optlen;
        }
        opt->ts = 0;
        opt->rr = 0;
        opt->rr_needaddr = 0;
        opt->ts_needaddr = 0;
        opt->ts_needtime = 0;
        return;
}

/*
 * Verify options and fill pointers in struct options.
 * Caller should clear *opt, and set opt->data.
 * If opt == NULL, then skb->data should point to IP header.
 */

int ip_options_compile(struct net *net,
                       struct ip_options * opt, struct sk_buff * skb)
{
        int l;
        unsigned char * iph;
        unsigned char * optptr;
        int optlen;
        unsigned char * pp_ptr = NULL;
        struct rtable *rt = NULL;

        if (skb != NULL) {
                rt = skb->rtable;
                optptr = (unsigned char *)&(ip_hdr(skb)[1]);
        } else
                optptr = opt->__data;
        iph = optptr - sizeof(struct iphdr);

        for (l = opt->optlen; l > 0; ) {
                switch (*optptr) {
                      case IPOPT_END:
                        for (optptr++, l--; l>0; optptr++, l--) {
                                if (*optptr != IPOPT_END) {
                                        *optptr = IPOPT_END;
                                        opt->is_changed = 1;
                                }
                        }
                        goto eol;
                      case IPOPT_NOOP:
                        l--;
                        optptr++;
                        continue;
                }
                optlen = optptr[1];
                if (optlen<2 || optlen>l) {
                        pp_ptr = optptr;
                        goto error;
                }
                switch (*optptr) {
                      case IPOPT_SSRR:
                      case IPOPT_LSRR:
                        if (optlen < 3) {
                                pp_ptr = optptr + 1;
                                goto error;
                        }
                        if (optptr[2] < 4) {
                                pp_ptr = optptr + 2;
                                goto error;
                        }
                        /* NB: cf RFC-1812 5.2.4.1 */
                        if (opt->srr) {
                                pp_ptr = optptr;
                                goto error;
                        }
                        if (!skb) {
                                if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
                                        pp_ptr = optptr + 1;
                                        goto error;
                                }
                                memcpy(&opt->faddr, &optptr[3], 4);
                                if (optlen > 7)
                                        memmove(&optptr[3], &optptr[7], optlen-7);
                        }
                        opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
                        opt->srr = optptr - iph;
                        break;
                      case IPOPT_RR:
                        if (opt->rr) {
                                pp_ptr = optptr;
                                goto error;
                        }
                        if (optlen < 3) {
                                pp_ptr = optptr + 1;
                                goto error;
                        }
                        if (optptr[2] < 4) {
                                pp_ptr = optptr + 2;
                                goto error;
                        }
                        if (optptr[2] <= optlen) {
                                if (optptr[2]+3 > optlen) {
                                        pp_ptr = optptr + 2;
                                        goto error;
                                }
                                if (skb) {
                                        memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
                                        opt->is_changed = 1;
                                }
                                optptr[2] += 4;
                                opt->rr_needaddr = 1;
                        }
                        opt->rr = optptr - iph;
                        break;
                      case IPOPT_TIMESTAMP:
                        if (opt->ts) {
                                pp_ptr = optptr;
                                goto error;
                        }
                        if (optlen < 4) {
                                pp_ptr = optptr + 1;
                                goto error;
                        }
                        if (optptr[2] < 5) {
                                pp_ptr = optptr + 2;
                                goto error;
                        }
                        if (optptr[2] <= optlen) {
                                __be32 *timeptr = NULL;
                                if (optptr[2]+3 > optptr[1]) {
                                        pp_ptr = optptr + 2;
                                        goto error;
                                }
                                switch (optptr[3]&0xF) {
                                      case IPOPT_TS_TSONLY:
                                        opt->ts = optptr - iph;
                                        if (skb)
                                                timeptr = (__be32*)&optptr[optptr[2]-1];
                                        opt->ts_needtime = 1;
                                        optptr[2] += 4;
                                        break;
                                      case IPOPT_TS_TSANDADDR:
                                        if (optptr[2]+7 > optptr[1]) {
                                                pp_ptr = optptr + 2;
                                                goto error;
                                        }
                                        opt->ts = optptr - iph;
                                        if (skb) {
                                                memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
                                                timeptr = (__be32*)&optptr[optptr[2]+3];
                                        }
                                        opt->ts_needaddr = 1;
                                        opt->ts_needtime = 1;
                                        optptr[2] += 8;
                                        break;
                                      case IPOPT_TS_PRESPEC:
                                        if (optptr[2]+7 > optptr[1]) {
                                                pp_ptr = optptr + 2;
                                                goto error;
                                        }
                                        opt->ts = optptr - iph;
                                        {
                                                __be32 addr;
                                                memcpy(&addr, &optptr[optptr[2]-1], 4);
                                                if (inet_addr_type(net, addr) == RTN_UNICAST)
                                                        break;
                                                if (skb)
                                                        timeptr = (__be32*)&optptr[optptr[2]+3];
                                        }
                                        opt->ts_needtime = 1;
                                        optptr[2] += 8;
                                        break;
                                      default:
                                        if (!skb && !capable(CAP_NET_RAW)) {
                                                pp_ptr = optptr + 3;
                                                goto error;
                                        }
                                        break;
                                }
                                if (timeptr) {
                                        struct timespec tv;
                                        __be32  midtime;
                                        getnstimeofday(&tv);
                                        midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
                                        memcpy(timeptr, &midtime, sizeof(__be32));
                                        opt->is_changed = 1;
                                }
                        } else {
                                unsigned overflow = optptr[3]>>4;
                                if (overflow == 15) {
                                        pp_ptr = optptr + 3;
                                        goto error;
                                }
                                opt->ts = optptr - iph;
                                if (skb) {
                                        optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
                                        opt->is_changed = 1;
                                }
                        }
                        break;
                      case IPOPT_RA:
                        if (optlen < 4) {
                                pp_ptr = optptr + 1;
                                goto error;
                        }
                        if (optptr[2] == 0 && optptr[3] == 0)
                                opt->router_alert = optptr - iph;
                        break;
                      case IPOPT_CIPSO:
                        if ((!skb && !capable(CAP_NET_RAW)) || opt->cipso) {
                                pp_ptr = optptr;
                                goto error;
                        }
                        opt->cipso = optptr - iph;
                        if (cipso_v4_validate(skb, &optptr)) {
                                pp_ptr = optptr;
                                goto error;
                        }
                        break;
                      case IPOPT_SEC:
                      case IPOPT_SID:
                      default:
                        if (!skb && !capable(CAP_NET_RAW)) {
                                pp_ptr = optptr;
                                goto error;
                        }
                        break;
                }
                l -= optlen;
                optptr += optlen;
        }

eol:
        if (!pp_ptr)
                return 0;

error:
        if (skb) {
                icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
        }
        return -EINVAL;
}


/*
 *      Undo all the changes done by ip_options_compile().
 */

void ip_options_undo(struct ip_options * opt)
{
        if (opt->srr) {
                unsigned  char * optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
                memmove(optptr+7, optptr+3, optptr[1]-7);
                memcpy(optptr+3, &opt->faddr, 4);
        }
        if (opt->rr_needaddr) {
                unsigned  char * optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
                optptr[2] -= 4;
                memset(&optptr[optptr[2]-1], 0, 4);
        }
        if (opt->ts) {
                unsigned  char * optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
                if (opt->ts_needtime) {
                        optptr[2] -= 4;
                        memset(&optptr[optptr[2]-1], 0, 4);
                        if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
                                optptr[2] -= 4;
                }
                if (opt->ts_needaddr) {
                        optptr[2] -= 4;
                        memset(&optptr[optptr[2]-1], 0, 4);
                }
        }
}

static struct ip_options *ip_options_get_alloc(const int optlen)
{
        return kzalloc(sizeof(struct ip_options) + ((optlen + 3) & ~3),
                       GFP_KERNEL);
}

static int ip_options_get_finish(struct net *net, struct ip_options **optp,
                                 struct ip_options *opt, int optlen)
{
        while (optlen & 3)
                opt->__data[optlen++] = IPOPT_END;
        opt->optlen = optlen;
        if (optlen && ip_options_compile(net, opt, NULL)) {
                kfree(opt);
                return -EINVAL;
        }
        kfree(*optp);
        *optp = opt;
        return 0;
}

int ip_options_get_from_user(struct net *net, struct ip_options **optp,
                             unsigned char __user *data, int optlen)
{
        struct ip_options *opt = ip_options_get_alloc(optlen);

        if (!opt)
                return -ENOMEM;
        if (optlen && copy_from_user(opt->__data, data, optlen)) {
                kfree(opt);
                return -EFAULT;
        }
        return ip_options_get_finish(net, optp, opt, optlen);
}

int ip_options_get(struct net *net, struct ip_options **optp,
                   unsigned char *data, int optlen)
{
        struct ip_options *opt = ip_options_get_alloc(optlen);

        if (!opt)
                return -ENOMEM;
        if (optlen)
                memcpy(opt->__data, data, optlen);
        return ip_options_get_finish(net, optp, opt, optlen);
}

void ip_forward_options(struct sk_buff *skb)
{
        struct   ip_options * opt       = &(IPCB(skb)->opt);
        unsigned char * optptr;
        struct rtable *rt = skb->rtable;
        unsigned char *raw = skb_network_header(skb);

        if (opt->rr_needaddr) {
                optptr = (unsigned char *)raw + opt->rr;
                ip_rt_get_source(&optptr[optptr[2]-5], rt);
                opt->is_changed = 1;
        }
        if (opt->srr_is_hit) {
                int srrptr, srrspace;

                optptr = raw + opt->srr;

                for ( srrptr=optptr[2], srrspace = optptr[1];
                     srrptr <= srrspace;
                     srrptr += 4
                     ) {
                        if (srrptr + 3 > srrspace)
                                break;
                        if (memcmp(&rt->rt_dst, &optptr[srrptr-1], 4) == 0)
                                break;
                }
                if (srrptr + 3 <= srrspace) {
                        opt->is_changed = 1;
                        ip_rt_get_source(&optptr[srrptr-1], rt);
                        ip_hdr(skb)->daddr = rt->rt_dst;
                        optptr[2] = srrptr+4;
                } else if (net_ratelimit())
                        printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
                if (opt->ts_needaddr) {
                        optptr = raw + opt->ts;
                        ip_rt_get_source(&optptr[optptr[2]-9], rt);
                        opt->is_changed = 1;
                }
        }
        if (opt->is_changed) {
                opt->is_changed = 0;
                ip_send_check(ip_hdr(skb));
        }
}

int ip_options_rcv_srr(struct sk_buff *skb)
{
        struct ip_options *opt = &(IPCB(skb)->opt);
        int srrspace, srrptr;
        __be32 nexthop;
        struct iphdr *iph = ip_hdr(skb);
        unsigned char *optptr = skb_network_header(skb) + opt->srr;
        struct rtable *rt = skb->rtable;
        struct rtable *rt2;
        int err;

        if (!opt->srr)
                return 0;

        if (skb->pkt_type != PACKET_HOST)
                return -EINVAL;
        if (rt->rt_type == RTN_UNICAST) {
                if (!opt->is_strictroute)
                        return 0;
                icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
                return -EINVAL;
        }
        if (rt->rt_type != RTN_LOCAL)
                return -EINVAL;

        for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
                if (srrptr + 3 > srrspace) {
                        icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
                        return -EINVAL;
                }
                memcpy(&nexthop, &optptr[srrptr-1], 4);

                rt = skb->rtable;
                skb->rtable = NULL;
                err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
                rt2 = skb->rtable;
                if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
                        ip_rt_put(rt2);
                        skb->rtable = rt;
                        return -EINVAL;
                }
                ip_rt_put(rt);
                if (rt2->rt_type != RTN_LOCAL)
                        break;
                /* Superfast 8) loopback forward */
                memcpy(&iph->daddr, &optptr[srrptr-1], 4);
                opt->is_changed = 1;
        }
        if (srrptr <= srrspace) {
                opt->srr_is_hit = 1;
                opt->is_changed = 1;
        }
        return 0;
}

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