From 9fd51e9b0ad33a89a83fdbbb66bd20d85f7893fb Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Fri, 4 Feb 2000 03:21:18 +0000 Subject: Import of Linux 2.2.12 subset (ipv4 stack and related) --- pfinet/linux-src/net/ipv4/ip_fragment.c | 593 ++++++++++++++++++++++++++++++++ 1 file changed, 593 insertions(+) create mode 100644 pfinet/linux-src/net/ipv4/ip_fragment.c (limited to 'pfinet/linux-src/net/ipv4/ip_fragment.c') diff --git a/pfinet/linux-src/net/ipv4/ip_fragment.c b/pfinet/linux-src/net/ipv4/ip_fragment.c new file mode 100644 index 00000000..f066e607 --- /dev/null +++ b/pfinet/linux-src/net/ipv4/ip_fragment.c @@ -0,0 +1,593 @@ +/* + * 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 1.40 1999/03/20 23:58:34 davem Exp $ + * + * Authors: Fred N. van Kempen + * Alan Cox + * + * 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. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* 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. + */ +int sysctl_ipfrag_high_thresh = 256*1024; +int sysctl_ipfrag_low_thresh = 192*1024; + +int sysctl_ipfrag_time = IP_FRAG_TIME; + +/* Describe an IP fragment. */ +struct ipfrag { + int offset; /* offset of fragment in IP datagram */ + int end; /* last byte of data in datagram */ + int len; /* length of this fragment */ + struct sk_buff *skb; /* complete received fragment */ + unsigned char *ptr; /* pointer into real fragment data */ + struct ipfrag *next; /* linked list pointers */ + struct ipfrag *prev; +}; + +/* Describe an entry in the "incomplete datagrams" queue. */ +struct ipq { + struct iphdr *iph; /* pointer to IP header */ + struct ipq *next; /* linked list pointers */ + struct ipfrag *fragments; /* linked list of received fragments */ + int len; /* total length of original datagram */ + short ihlen; /* length of the IP header */ + struct timer_list timer; /* when will this queue expire? */ + struct ipq **pprev; + struct device *dev; /* Device - for icmp replies */ +}; + +#define IPQ_HASHSZ 64 + +struct ipq *ipq_hash[IPQ_HASHSZ]; + +#define ipqhashfn(id, saddr, daddr, prot) \ + ((((id) >> 1) ^ (saddr) ^ (daddr) ^ (prot)) & (IPQ_HASHSZ - 1)) + +atomic_t ip_frag_mem = ATOMIC_INIT(0); /* Memory used for fragments */ + +/* Memory Tracking Functions. */ +extern __inline__ void frag_kfree_skb(struct sk_buff *skb) +{ + atomic_sub(skb->truesize, &ip_frag_mem); + kfree_skb(skb); +} + +extern __inline__ void frag_kfree_s(void *ptr, int len) +{ + atomic_sub(len, &ip_frag_mem); + kfree(ptr); +} + +extern __inline__ void *frag_kmalloc(int size, int pri) +{ + void *vp = kmalloc(size, pri); + + if(!vp) + return NULL; + atomic_add(size, &ip_frag_mem); + return vp; +} + +/* Create a new fragment entry. */ +static struct ipfrag *ip_frag_create(int offset, int end, + struct sk_buff *skb, unsigned char *ptr) +{ + struct ipfrag *fp; + + fp = (struct ipfrag *) frag_kmalloc(sizeof(struct ipfrag), GFP_ATOMIC); + if (fp == NULL) + goto out_nomem; + + /* Fill in the structure. */ + fp->offset = offset; + fp->end = end; + fp->len = end - offset; + fp->skb = skb; + fp->ptr = ptr; + fp->next = fp->prev = NULL; + + /* Charge for the SKB as well. */ + atomic_add(skb->truesize, &ip_frag_mem); + + return(fp); + +out_nomem: + NETDEBUG(printk(KERN_ERR "IP: frag_create: no memory left !\n")); + return(NULL); +} + +/* Find the correct entry in the "incomplete datagrams" queue for + * this IP datagram, and return the queue entry address if found. + */ +static inline struct ipq *ip_find(struct iphdr *iph, struct dst_entry *dst) +{ + __u16 id = iph->id; + __u32 saddr = iph->saddr; + __u32 daddr = iph->daddr; + __u8 protocol = iph->protocol; + unsigned int hash = ipqhashfn(id, saddr, daddr, protocol); + struct ipq *qp; + + /* Always, we are in a BH context, so no locking. -DaveM */ + for(qp = ipq_hash[hash]; qp; qp = qp->next) { + if(qp->iph->id == id && + qp->iph->saddr == saddr && + qp->iph->daddr == daddr && + qp->iph->protocol == protocol) { + del_timer(&qp->timer); + break; + } + } + return qp; +} + +/* Remove an entry from the "incomplete datagrams" queue, either + * because we completed, reassembled and processed it, or because + * it timed out. + * + * This is called _only_ from BH contexts, on packet reception + * processing and from frag queue expiration timers. -DaveM + */ +static void ip_free(struct ipq *qp) +{ + struct ipfrag *fp; + + /* Stop the timer for this entry. */ + del_timer(&qp->timer); + + /* Remove this entry from the "incomplete datagrams" queue. */ + if(qp->next) + qp->next->pprev = qp->pprev; + *qp->pprev = qp->next; + + /* Release all fragment data. */ + fp = qp->fragments; + while (fp) { + struct ipfrag *xp = fp->next; + + frag_kfree_skb(fp->skb); + frag_kfree_s(fp, sizeof(struct ipfrag)); + fp = xp; + } + + /* Release the IP header. */ + frag_kfree_s(qp->iph, 64 + 8); + + /* Finally, release the queue descriptor itself. */ + frag_kfree_s(qp, sizeof(struct ipq)); +} + +/* + * Oops, a fragment queue timed out. Kill it and send an ICMP reply. + */ +static void ip_expire(unsigned long arg) +{ + struct ipq *qp = (struct ipq *) arg; + + if(!qp->fragments) + { +#ifdef IP_EXPIRE_DEBUG + printk("warning: possible ip-expire attack\n"); +#endif + goto out; + } + + /* Send an ICMP "Fragment Reassembly Timeout" message. */ + ip_statistics.IpReasmTimeout++; + ip_statistics.IpReasmFails++; + icmp_send(qp->fragments->skb, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); + +out: + /* Nuke the fragment queue. */ + ip_free(qp); +} + +/* Memory limiting on fragments. Evictor trashes the oldest + * fragment queue until we are back under the low threshold. + */ +static void ip_evictor(void) +{ + int i, progress; + +restart: + progress = 0; + /* FIXME: Make LRU queue of frag heads. -DaveM */ + for (i = 0; i < IPQ_HASHSZ; i++) { + struct ipq *qp; + if (atomic_read(&ip_frag_mem) <= sysctl_ipfrag_low_thresh) + return; + /* We are in a BH context, so these queue + * accesses are safe. -DaveM + */ + qp = ipq_hash[i]; + if (qp) { + /* find the oldest queue for this hash bucket */ + while (qp->next) + qp = qp->next; + ip_free(qp); + progress = 1; + } + } + if (progress) + goto restart; + panic("ip_evictor: memcount"); +} + +/* Add an entry to the 'ipq' queue for a newly received IP datagram. + * We will (hopefully :-) receive all other fragments of this datagram + * in time, so we just create a queue for this datagram, in which we + * will insert the received fragments at their respective positions. + */ +static struct ipq *ip_create(struct sk_buff *skb, struct iphdr *iph) +{ + struct ipq *qp; + unsigned int hash; + int ihlen; + + qp = (struct ipq *) frag_kmalloc(sizeof(struct ipq), GFP_ATOMIC); + if (qp == NULL) + goto out_nomem; + + /* Allocate memory for the IP header (plus 8 octets for ICMP). */ + ihlen = iph->ihl * 4; + + qp->iph = (struct iphdr *) frag_kmalloc(64 + 8, GFP_ATOMIC); + if (qp->iph == NULL) + goto out_free; + + memcpy(qp->iph, iph, ihlen + 8); + qp->len = 0; + qp->ihlen = ihlen; + qp->fragments = NULL; + qp->dev = skb->dev; + + /* Initialize a timer for this entry. */ + init_timer(&qp->timer); + qp->timer.expires = 0; /* (to be set later) */ + qp->timer.data = (unsigned long) qp; /* pointer to queue */ + qp->timer.function = ip_expire; /* expire function */ + + /* Add this entry to the queue. */ + hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol); + + /* We are in a BH context, no locking necessary. -DaveM */ + if((qp->next = ipq_hash[hash]) != NULL) + qp->next->pprev = &qp->next; + ipq_hash[hash] = qp; + qp->pprev = &ipq_hash[hash]; + + return qp; + +out_free: + frag_kfree_s(qp, sizeof(struct ipq)); +out_nomem: + NETDEBUG(printk(KERN_ERR "IP: create: no memory left !\n")); + return(NULL); +} + +/* See if a fragment queue is complete. */ +static int ip_done(struct ipq *qp) +{ + struct ipfrag *fp; + int offset; + + /* Only possible if we received the final fragment. */ + if (qp->len == 0) + return 0; + + /* Check all fragment offsets to see if they connect. */ + fp = qp->fragments; + offset = 0; + while (fp) { + if (fp->offset > offset) + return(0); /* fragment(s) missing */ + offset = fp->end; + fp = fp->next; + } + + /* All fragments are present. */ + return 1; +} + +/* Build a new IP datagram from all its fragments. + * + * FIXME: We copy here because we lack an effective way of handling lists + * of bits on input. Until the new skb data handling is in I'm not going + * to touch this with a bargepole. + */ +static struct sk_buff *ip_glue(struct ipq *qp) +{ + struct sk_buff *skb; + struct iphdr *iph; + struct ipfrag *fp; + unsigned char *ptr; + int count, len; + + /* Allocate a new buffer for the datagram. */ + len = qp->ihlen + qp->len; + + if(len > 65535) + goto out_oversize; + + skb = dev_alloc_skb(len); + if (!skb) + goto out_nomem; + + /* Fill in the basic details. */ + skb->mac.raw = ptr = skb->data; + skb->nh.iph = iph = (struct iphdr *) skb_put(skb, len); + + /* Copy the original IP headers into the new buffer. */ + memcpy(ptr, qp->iph, qp->ihlen); + ptr += qp->ihlen; + + /* Copy the data portions of all fragments into the new buffer. */ + fp = qp->fragments; + count = qp->ihlen; + while(fp) { + if ((fp->len <= 0) || ((count + fp->len) > skb->len)) + goto out_invalid; + memcpy((ptr + fp->offset), fp->ptr, fp->len); + if (count == qp->ihlen) { + skb->dst = dst_clone(fp->skb->dst); + skb->dev = fp->skb->dev; + } + count += fp->len; + fp = fp->next; + } + + skb->pkt_type = qp->fragments->skb->pkt_type; + skb->protocol = qp->fragments->skb->protocol; + /* + * Clearly bogus, because security markings of the individual + * fragments should have been checked for consistency before + * gluing, and intermediate coalescing of fragments may have + * taken place in ip_defrag() before ip_glue() ever got called. + * If we're not going to do the consistency checking, we might + * as well take the value associated with the first fragment. + * --rct + */ + skb->security = qp->fragments->skb->security; + + /* Done with all fragments. Fixup the new IP header. */ + iph = skb->nh.iph; + iph->frag_off = 0; + iph->tot_len = htons(count); + ip_statistics.IpReasmOKs++; + return skb; + +out_invalid: + NETDEBUG(printk(KERN_ERR + "Invalid fragment list: Fragment over size.\n")); + kfree_skb(skb); + goto out_fail; +out_nomem: + NETDEBUG(printk(KERN_ERR + "IP: queue_glue: no memory for gluing queue %p\n", + qp)); + goto out_fail; +out_oversize: + if (net_ratelimit()) + printk(KERN_INFO + "Oversized IP packet from %d.%d.%d.%d.\n", + NIPQUAD(qp->iph->saddr)); +out_fail: + ip_statistics.IpReasmFails++; + return NULL; +} + +/* Process an incoming IP datagram fragment. */ +struct sk_buff *ip_defrag(struct sk_buff *skb) +{ + struct iphdr *iph = skb->nh.iph; + struct ipfrag *prev, *next, *tmp, *tfp; + struct ipq *qp; + unsigned char *ptr; + int flags, offset; + int i, ihl, end; + + ip_statistics.IpReasmReqds++; + + /* Start by cleaning up the memory. */ + if (atomic_read(&ip_frag_mem) > sysctl_ipfrag_high_thresh) + ip_evictor(); + + /* + * Look for the entry for this IP datagram in the + * "incomplete datagrams" queue. If found, the + * timer is removed. + */ + qp = ip_find(iph, skb->dst); + + /* Is this a non-fragmented datagram? */ + offset = ntohs(iph->frag_off); + flags = offset & ~IP_OFFSET; + offset &= IP_OFFSET; + + offset <<= 3; /* offset is in 8-byte chunks */ + ihl = iph->ihl * 4; + + /* + * Check whether to create a fresh queue entry. If the + * queue already exists, its timer will be restarted as + * long as we continue to receive fragments. + */ + if (qp) { + /* ANK. If the first fragment is received, + * we should remember the correct IP header (with options) + */ + if (offset == 0) { + /* Fragmented frame replaced by unfragmented copy? */ + if ((flags & IP_MF) == 0) + goto out_freequeue; + qp->ihlen = ihl; + memcpy(qp->iph, iph, (ihl + 8)); + } + } else { + /* Fragmented frame replaced by unfragmented copy? */ + if ((offset == 0) && ((flags & IP_MF) == 0)) + goto out_skb; + + /* If we failed to create it, then discard the frame. */ + qp = ip_create(skb, iph); + if (!qp) + goto out_freeskb; + } + + /* Attempt to construct an oversize packet. */ + if((ntohs(iph->tot_len) + ((int) offset)) > 65535) + goto out_oversize; + + /* Determine the position of this fragment. */ + end = offset + ntohs(iph->tot_len) - ihl; + + /* Is this the final fragment? */ + if ((flags & IP_MF) == 0) + qp->len = end; + + /* 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->fragments; next != NULL; next = next->next) { + if (next->offset >= offset) + break; /* bingo! */ + prev = next; + } + + /* Point into the IP datagram 'data' part. */ + ptr = skb->data + ihl; + + /* 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 != NULL) && (offset < prev->end)) { + i = prev->end - offset; + offset += i; /* ptr into datagram */ + ptr += i; /* ptr into fragment data */ + } + + /* Look for overlap with succeeding segments. + * If we can merge fragments, do it. + */ + for (tmp = next; tmp != NULL; tmp = tfp) { + tfp = tmp->next; + if (tmp->offset >= end) + break; /* no overlaps at all */ + + i = end - next->offset; /* overlap is 'i' bytes */ + tmp->len -= i; /* so reduce size of */ + tmp->offset += i; /* next fragment */ + tmp->ptr += i; + + /* If we get a frag size of <= 0, remove it and the packet + * that it goes with. + */ + if (tmp->len <= 0) { + if (tmp->prev != NULL) + tmp->prev->next = tmp->next; + else + qp->fragments = tmp->next; + + if (tmp->next != NULL) + tmp->next->prev = tmp->prev; + + /* We have killed the original next frame. */ + next = tfp; + + frag_kfree_skb(tmp->skb); + frag_kfree_s(tmp, sizeof(struct ipfrag)); + } + } + + /* + * Create a fragment to hold this skb. + * No memory to save the fragment? throw the lot ... + */ + tfp = ip_frag_create(offset, end, skb, ptr); + if (!tfp) + goto out_freeskb; + + /* Insert this fragment in the chain of fragments. */ + tfp->prev = prev; + tfp->next = next; + if (prev != NULL) + prev->next = tfp; + else + qp->fragments = tfp; + + if (next != NULL) + next->prev = tfp; + + /* OK, so we inserted this new fragment into the chain. + * Check if we now have a full IP datagram which we can + * bump up to the IP layer... + */ + if (ip_done(qp)) { + /* Glue together the fragments. */ + skb = ip_glue(qp); + /* Free the queue entry. */ +out_freequeue: + ip_free(qp); +out_skb: + return skb; + } + + /* + * The queue is still active ... reset its timer. + */ +out_timer: + mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time); /* ~ 30 seconds */ +out: + return NULL; + + /* + * Error exits ... we need to reset the timer if there's a queue. + */ +out_oversize: + if (net_ratelimit()) + printk(KERN_INFO "Oversized packet received from %d.%d.%d.%d\n", + NIPQUAD(iph->saddr)); + /* the skb isn't in a fragment, so fall through to free it */ +out_freeskb: + kfree_skb(skb); + ip_statistics.IpReasmFails++; + if (qp) + goto out_timer; + goto out; +} -- cgit v1.2.3