Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

/*

 * 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 IP fragmentation functionality.

 *

 * Version:     $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $

 *

 * Authors:     Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>

 *              Alan Cox <Alan.Cox@linux.org>

 *

 * Fixes:

 *              Alan Cox        :       Split from ip.c , see ip_input.c for history.

 *              David S. Miller :       Begin massive cleanup...

 *              Andi Kleen      :       Add sysctls.

 *              xxxx            :       Overlapfrag bug.

 *              Ultima          :       ip_expire() kernel panic.

 *              Bill Hawes      :       Frag accounting and evictor fixes.

 *              John McDonald   :       0 length frag bug.

 *              Alexey Kuznetsov:       SMP races, threading, cleanup.

 *              Patrick McHardy :       LRU queue of frag heads for evictor.

 */

#include <linux/compiler.h>

#include <linux/module.h>

#include <linux/types.h>

#include <linux/mm.h>

#include <linux/jiffies.h>

#include <linux/skbuff.h>

#include <linux/list.h>

#include <linux/ip.h>

#include <linux/icmp.h>

#include <linux/netdevice.h>

#include <linux/jhash.h>

#include <linux/random.h>

#include <net/sock.h>

#include <net/ip.h>

#include <net/icmp.h>

#include <net/checksum.h>

#include <net/inetpeer.h>

#include <net/inet_frag.h>

#include <linux/tcp.h>

#include <linux/udp.h>

#include <linux/inet.h>

#include <linux/netfilter_ipv4.h>

/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6

 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c

 * as well. Or notify me, at least. --ANK

 */

int sysctl_ipfrag_max_dist __read_mostly = 64;

struct ipfrag_skb_cb

{

        struct inet_skb_parm    h;

        int                     offset;

};

#define FRAG_CB(skb)    ((struct ipfrag_skb_cb*)((skb)->cb))

/* Describe an entry in the "incomplete datagrams" queue. */

struct ipq {

        struct inet_frag_queue q;

        u32             user;

        __be32          saddr;

        __be32          daddr;

        __be16          id;

        u8              protocol;

        int             iif;

        unsigned int    rid;

        struct inet_peer *peer;

};

struct inet_frags_ctl ip4_frags_ctl __read_mostly = {

        /*

         * Fragment cache limits. We will commit 256K at one time. Should we

         * cross that limit we will prune down to 192K. This should cope with

         * even the most extreme cases without allowing an attacker to

         * measurably harm machine performance.

         */

        .high_thresh     = 256 * 1024,

        .low_thresh      = 192 * 1024,

        /*

         * Important NOTE! Fragment queue must be destroyed before MSL expires.

         * RFC791 is wrong proposing to prolongate timer each fragment arrival

         * by TTL.

         */

        .timeout         = IP_FRAG_TIME,

        .secret_interval = 10 * 60 * HZ,

};

static struct inet_frags ip4_frags;

int ip_frag_nqueues(void)

{

        return ip4_frags.nqueues;

}

int ip_frag_mem(void)

{

        return atomic_read(&ip4_frags.mem);

}

static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,

                         struct net_device *dev);

struct ip4_create_arg {

        struct iphdr *iph;

        u32 user;

};

static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)

{

        return jhash_3words((__force u32)id << 16 | prot,

                            (__force u32)saddr, (__force u32)daddr,

                            ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);

}

static unsigned int ip4_hashfn(struct inet_frag_queue *q)

{

        struct ipq *ipq;

        ipq = container_of(q, struct ipq, q);

        return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);

}

static int ip4_frag_match(struct inet_frag_queue *q, void *a)

{

        struct ipq *qp;

        struct ip4_create_arg *arg = a;

        qp = container_of(q, struct ipq, q);

        return (qp->id == arg->iph->id &&

                        qp->saddr == arg->iph->saddr &&

                        qp->daddr == arg->iph->daddr &&

                        qp->protocol == arg->iph->protocol &&

                        qp->user == arg->user);

}

/* Memory Tracking Functions. */

static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)

{

        if (work)

                *work -= skb->truesize;

        atomic_sub(skb->truesize, &ip4_frags.mem);

        kfree_skb(skb);

}

static void ip4_frag_init(struct inet_frag_queue *q, void *a)

{

        struct ipq *qp = container_of(q, struct ipq, q);

        struct ip4_create_arg *arg = a;

        qp->protocol = arg->iph->protocol;

        qp->id = arg->iph->id;

        qp->saddr = arg->iph->saddr;

        qp->daddr = arg->iph->daddr;

        qp->user = arg->user;

        qp->peer = sysctl_ipfrag_max_dist ?

                inet_getpeer(arg->iph->saddr, 1) : NULL;

}

static __inline__ void ip4_frag_free(struct inet_frag_queue *q)

{

        struct ipq *qp;

        qp = container_of(q, struct ipq, q);

        if (qp->peer)

                inet_putpeer(qp->peer);

}

/* Destruction primitives. */

static __inline__ void ipq_put(struct ipq *ipq)

{

        inet_frag_put(&ipq->q, &ip4_frags);

}

/* Kill ipq entry. It is not destroyed immediately,

 * because caller (and someone more) holds reference count.

 */

static void ipq_kill(struct ipq *ipq)

{

        inet_frag_kill(&ipq->q, &ip4_frags);

}

/* Memory limiting on fragments.  Evictor trashes the oldest

 * fragment queue until we are back under the threshold.

 */

static void ip_evictor(void)

{

        int evicted;

        evicted = inet_frag_evictor(&ip4_frags);

        if (evicted)

                IP_ADD_STATS_BH(IPSTATS_MIB_REASMFAILS, evicted);

}

/*

 * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.

 */

static void ip_expire(unsigned long arg)

{

        struct ipq *qp;

        qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);

        spin_lock(&qp->q.lock);

        if (qp->q.last_in & COMPLETE)

                goto out;

        ipq_kill(qp);

        IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);

        IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);

        if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) {

                struct sk_buff *head = qp->q.fragments;

                /* Send an ICMP "Fragment Reassembly Timeout" message. */

                if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {

                        icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);

                        dev_put(head->dev);

                }

        }

out:

        spin_unlock(&qp->q.lock);

        ipq_put(qp);

}

/* Find the correct entry in the "incomplete datagrams" queue for

 * this IP datagram, and create new one, if nothing is found.

 */

static inline struct ipq *ip_find(struct iphdr *iph, u32 user)

{

        struct inet_frag_queue *q;

        struct ip4_create_arg arg;

        unsigned int hash;

        arg.iph = iph;

        arg.user = user;

        hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);

        q = inet_frag_find(&ip4_frags, &arg, hash);

        if (q == NULL)

                goto out_nomem;

        return container_of(q, struct ipq, q);

out_nomem:

        LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");

        return NULL;

}

/* Is the fragment too far ahead to be part of ipq? */

static inline int ip_frag_too_far(struct ipq *qp)

{

        struct inet_peer *peer = qp->peer;

        unsigned int max = sysctl_ipfrag_max_dist;

        unsigned int start, end;

        int rc;

        if (!peer || !max)

                return 0;

        start = qp->rid;

        end = atomic_inc_return(&peer->rid);

        qp->rid = end;

        rc = qp->q.fragments && (end - start) > max;

        if (rc) {

                IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);

        }

        return rc;

}

static int ip_frag_reinit(struct ipq *qp)

{

        struct sk_buff *fp;

        if (!mod_timer(&qp->q.timer, jiffies + ip4_frags_ctl.timeout)) {

                atomic_inc(&qp->q.refcnt);

                return -ETIMEDOUT;

        }

        fp = qp->q.fragments;

        do {

                struct sk_buff *xp = fp->next;

                frag_kfree_skb(fp, NULL);

                fp = xp;

        } while (fp);

        qp->q.last_in = 0;

        qp->q.len = 0;

        qp->q.meat = 0;

        qp->q.fragments = NULL;

        qp->iif = 0;

        return 0;

}

/* Add new segment to existing queue. */

static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)

{

        struct sk_buff *prev, *next;

        struct net_device *dev;

        int flags, offset;

        int ihl, end;

        int err = -ENOENT;

        if (qp->q.last_in & COMPLETE)

                goto err;

        if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&

            unlikely(ip_frag_too_far(qp)) &&

            unlikely(err = ip_frag_reinit(qp))) {

                ipq_kill(qp);

                goto err;

        }

        offset = ntohs(ip_hdr(skb)->frag_off);

        flags = offset & ~IP_OFFSET;

        offset &= IP_OFFSET;

        offset <<= 3;           /* offset is in 8-byte chunks */

        ihl = ip_hdrlen(skb);

        /* Determine the position of this fragment. */

        end = offset + skb->len - ihl;

        err = -EINVAL;

        /* Is this the final fragment? */

        if ((flags & IP_MF) == 0) {

                /* If we already have some bits beyond end

                 * or have different end, the segment is corrrupted.

                 */

                if (end < qp->q.len ||

                    ((qp->q.last_in & LAST_IN) && end != qp->q.len))

                        goto err;

                qp->q.last_in |= LAST_IN;

                qp->q.len = end;

        } else {

                if (end&7) {

                        end &= ~7;

                        if (skb->ip_summed != CHECKSUM_UNNECESSARY)

                                skb->ip_summed = CHECKSUM_NONE;

                }

                if (end > qp->q.len) {

                        /* Some bits beyond end -> corruption. */

                        if (qp->q.last_in & LAST_IN)

                                goto err;

                        qp->q.len = end;

                }

        }

        if (end == offset)

                goto err;

        err = -ENOMEM;

        if (pskb_pull(skb, ihl) == NULL)

                goto err;

        err = pskb_trim_rcsum(skb, end - offset);

        if (err)

                goto err;

        /* Find out which fragments are in front and at the back of us

         * in the chain of fragments so far.  We must know where to put

         * this fragment, right?

         */

        prev = NULL;

        for (next = qp->q.fragments; next != NULL; next = next->next) {

                if (FRAG_CB(next)->offset >= offset)

                        break;  /* bingo! */

                prev = next;

        }

        /* We found where to put this one.  Check for overlap with

         * preceding fragment, and, if needed, align things so that

         * any overlaps are eliminated.

         */

        if (prev) {

                int i = (FRAG_CB(prev)->offset + prev->len) - offset;

                if (i > 0) {

                        offset += i;

                        err = -EINVAL;

                        if (end <= offset)

                                goto err;

                        err = -ENOMEM;

                        if (!pskb_pull(skb, i))

                                goto err;

                        if (skb->ip_summed != CHECKSUM_UNNECESSARY)

                                skb->ip_summed = CHECKSUM_NONE;

                }

        }

        err = -ENOMEM;

        while (next && FRAG_CB(next)->offset < end) {

                int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */

                if (i < next->len) {

                        /* Eat head of the next overlapped fragment

                         * and leave the loop. The next ones cannot overlap.

                         */

                        if (!pskb_pull(next, i))

                                goto err;

                        FRAG_CB(next)->offset += i;

                        qp->q.meat -= i;

                        if (next->ip_summed != CHECKSUM_UNNECESSARY)

                                next->ip_summed = CHECKSUM_NONE;

                        break;

                } else {

                        struct sk_buff *free_it = next;

                        /* Old fragment is completely overridden with

                         * new one drop it.

                         */

                        next = next->next;

                        if (prev)

                                prev->next = next;

                        else

                                qp->q.fragments = next;

                        qp->q.meat -= free_it->len;

                        frag_kfree_skb(free_it, NULL);

                }

        }

        FRAG_CB(skb)->offset = offset;

        /* Insert this fragment in the chain of fragments. */

        skb->next = next;

        if (prev)

                prev->next = skb;

        else

                qp->q.fragments = skb;

        dev = skb->dev;

        if (dev) {

                qp->iif = dev->ifindex;

                skb->dev = NULL;

        }

        qp->q.stamp = skb->tstamp;

        qp->q.meat += skb->len;

        atomic_add(skb->truesize, &ip4_frags.mem);

        if (offset == 0)

                qp->q.last_in |= FIRST_IN;

        if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len)

                return ip_frag_reasm(qp, prev, dev);

        write_lock(&ip4_frags.lock);

        list_move_tail(&qp->q.lru_list, &ip4_frags.lru_list);

        write_unlock(&ip4_frags.lock);

        return -EINPROGRESS;

err:

        kfree_skb(skb);

        return err;

}

/* Build a new IP datagram from all its fragments. */

static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,

                         struct net_device *dev)

{

        struct iphdr *iph;

        struct sk_buff *fp, *head = qp->q.fragments;

        int len;

        int ihlen;

        int err;

        ipq_kill(qp);

        /* Make the one we just received the head. */

        if (prev) {

                head = prev->next;

                fp = skb_clone(head, GFP_ATOMIC);

                if (!fp)

                        goto out_nomem;

                fp->next = head->next;

                prev->next = fp;

                skb_morph(head, qp->q.fragments);

                head->next = qp->q.fragments->next;

                kfree_skb(qp->q.fragments);

                qp->q.fragments = head;

        }

        BUG_TRAP(head != NULL);

        BUG_TRAP(FRAG_CB(head)->offset == 0);

        /* Allocate a new buffer for the datagram. */

        ihlen = ip_hdrlen(head);

        len = ihlen + qp->q.len;

        err = -E2BIG;

        if (len > 65535)

                goto out_oversize;

        /* Head of list must not be cloned. */

        if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))

                goto out_nomem;

        /* If the first fragment is fragmented itself, we split

         * it to two chunks: the first with data and paged part

         * and the second, holding only fragments. */

        if (skb_shinfo(head)->frag_list) {

                struct sk_buff *clone;

                int i, plen = 0;

                if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)

                        goto out_nomem;

                clone->next = head->next;

                head->next = clone;

                skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;

                skb_shinfo(head)->frag_list = NULL;

                for (i=0; i<skb_shinfo(head)->nr_frags; i++)

                        plen += skb_shinfo(head)->frags[i].size;

                clone->len = clone->data_len = head->data_len - plen;

                head->data_len -= clone->len;

                head->len -= clone->len;

                clone->csum = 0;

                clone->ip_summed = head->ip_summed;

                atomic_add(clone->truesize, &ip4_frags.mem);

        }

        skb_shinfo(head)->frag_list = head->next;

        skb_push(head, head->data - skb_network_header(head));

        atomic_sub(head->truesize, &ip4_frags.mem);

        for (fp=head->next; fp; fp = fp->next) {

                head->data_len += fp->len;

                head->len += fp->len;

                if (head->ip_summed != fp->ip_summed)

                        head->ip_summed = CHECKSUM_NONE;

                else if (head->ip_summed == CHECKSUM_COMPLETE)

                        head->csum = csum_add(head->csum, fp->csum);

                head->truesize += fp->truesize;

                atomic_sub(fp->truesize, &ip4_frags.mem);

        }

        head->next = NULL;

        head->dev = dev;

        head->tstamp = qp->q.stamp;

        iph = ip_hdr(head);

        iph->frag_off = 0;

        iph->tot_len = htons(len);

        IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);

        qp->q.fragments = NULL;

        return 0;

out_nomem:

        LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "

                              "queue %p\n", qp);

        err = -ENOMEM;

        goto out_fail;

out_oversize:

        if (net_ratelimit())

                printk(KERN_INFO

                        "Oversized IP packet from %d.%d.%d.%d.\n",

                        NIPQUAD(qp->saddr));

out_fail:

        IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);

        return err;

}

/* Process an incoming IP datagram fragment. */

int ip_defrag(struct sk_buff *skb, u32 user)

{

        struct ipq *qp;

        IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);

        /* Start by cleaning up the memory. */

        if (atomic_read(&ip4_frags.mem) > ip4_frags_ctl.high_thresh)

                ip_evictor();

        /* Lookup (or create) queue header */

        if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {

                int ret;

                spin_lock(&qp->q.lock);

                ret = ip_frag_queue(qp, skb);

                spin_unlock(&qp->q.lock);

                ipq_put(qp);

                return ret;

        }

        IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);

        kfree_skb(skb);

        return -ENOMEM;

}

void __init ipfrag_init(void)

{

        ip4_frags.ctl = &ip4_frags_ctl;

        ip4_frags.hashfn = ip4_hashfn;

        ip4_frags.constructor = ip4_frag_init;

        ip4_frags.destructor = ip4_frag_free;

        ip4_frags.skb_free = NULL;

        ip4_frags.qsize = sizeof(struct ipq);

        ip4_frags.match = ip4_frag_match;

        ip4_frags.frag_expire = ip_expire;

        inet_frags_init(&ip4_frags);

}

EXPORT_SYMBOL(ip_defrag);