URL
https://opencores.org/ocsvn/or1k/or1k/trunk
Subversion Repositories or1k
[/] [or1k/] [trunk/] [rc203soc/] [sw/] [uClinux/] [net/] [ipv4/] [ip_fragment.c] - Rev 1772
Go to most recent revision | Compare with Previous | Blame | View Log
/* * 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. * * 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. * Alan Cox : Handling oversized frames * Uriel Maimon : Accounting errors in two fringe cases. */ #include <linux/types.h> #include <linux/mm.h> #include <linux/sched.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <linux/icmp.h> #include <linux/netdevice.h> #include <net/sock.h> #include <net/ip.h> #include <net/icmp.h> #include <linux/tcp.h> #include <linux/udp.h> #include <linux/inet.h> #include <linux/firewall.h> #include <linux/ip_fw.h> #include <net/checksum.h> /* * 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. */ #define IPFRAG_HIGH_THRESH (256*1024) #define IPFRAG_LOW_THRESH (192*1024) /* * This fragment handler is a bit of a heap. On the other hand it works quite * happily and handles things quite well. */ static struct ipq *ipqueue = NULL; /* IP fragment queue */ atomic_t ip_frag_mem = 0; /* Memory used for fragments */ char *in_ntoa(unsigned long in); /* * Memory Tracking Functions */ extern __inline__ void frag_kfree_skb(struct sk_buff *skb, int type) { atomic_sub(skb->truesize, &ip_frag_mem); kfree_skb(skb,type); } extern __inline__ void frag_kfree_s(void *ptr, int len) { atomic_sub(len, &ip_frag_mem); kfree_s(ptr,len); } 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; unsigned long flags; fp = (struct ipfrag *) frag_kmalloc(sizeof(struct ipfrag), GFP_ATOMIC); if (fp == NULL) { NETDEBUG(printk("IP: frag_create: no memory left !\n")); return(NULL); } memset(fp, 0, sizeof(struct ipfrag)); /* Fill in the structure. */ fp->offset = offset; fp->end = end; fp->len = end - offset; fp->skb = skb; fp->ptr = ptr; /* * Charge for the SKB as well. */ save_flags(flags); cli(); ip_frag_mem+=skb->truesize; restore_flags(flags); return(fp); } /* * Find the correct entry in the "incomplete datagrams" queue for * this IP datagram, and return the queue entry address if found. */ static struct ipq *ip_find(struct iphdr *iph) { struct ipq *qp; struct ipq *qplast; cli(); qplast = NULL; for(qp = ipqueue; qp != NULL; qplast = qp, qp = qp->next) { if (iph->id== qp->iph->id && iph->saddr == qp->iph->saddr && iph->daddr == qp->iph->daddr && iph->protocol == qp->iph->protocol) { del_timer(&qp->timer); /* So it doesn't vanish on us. The timer will be reset anyway */ sti(); return(qp); } } sti(); return(NULL); } /* * Remove an entry from the "incomplete datagrams" queue, either * because we completed, reassembled and processed it, or because * it timed out. */ static void ip_free(struct ipq *qp) { struct ipfrag *fp; struct ipfrag *xp; /* * Stop the timer for this entry. */ del_timer(&qp->timer); /* Remove this entry from the "incomplete datagrams" queue. */ cli(); if (qp->prev == NULL) { ipqueue = qp->next; if (ipqueue != NULL) ipqueue->prev = NULL; } else { qp->prev->next = qp->next; if (qp->next != NULL) qp->next->prev = qp->prev; } /* Release all fragment data. */ fp = qp->fragments; while (fp != NULL) { xp = fp->next; IS_SKB(fp->skb); frag_kfree_skb(fp->skb,FREE_READ); 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)); sti(); } /* * Oops- a fragment queue timed out. Kill it and send an ICMP reply. */ static void ip_expire(unsigned long arg) { struct ipq *qp; qp = (struct ipq *)arg; /* * Send an ICMP "Fragment Reassembly Timeout" message. */ ip_statistics.IpReasmTimeout++; ip_statistics.IpReasmFails++; /* This if is always true... shrug */ if(qp->fragments!=NULL) icmp_send(qp->fragments->skb,ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0, qp->dev); /* * 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) { while(ip_frag_mem>IPFRAG_LOW_THRESH) { if(!ipqueue) panic("ip_evictor: memcount"); ip_free(ipqueue); } } /* * 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 device *dev) { struct ipq *qp; int ihlen; qp = (struct ipq *) frag_kmalloc(sizeof(struct ipq), GFP_ATOMIC); if (qp == NULL) { NETDEBUG(printk("IP: create: no memory left !\n")); return(NULL); } memset(qp, 0, sizeof(struct ipq)); /* * 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) { NETDEBUG(printk("IP: create: no memory left !\n")); frag_kfree_s(qp, sizeof(struct ipq)); return(NULL); } memcpy(qp->iph, iph, ihlen + 8); qp->len = 0; qp->ihlen = ihlen; qp->fragments = NULL; qp->dev = dev; /* Start a timer for this entry. */ qp->timer.expires = jiffies + IP_FRAG_TIME; /* about 30 seconds */ qp->timer.data = (unsigned long) qp; /* pointer to queue */ qp->timer.function = ip_expire; /* expire function */ add_timer(&qp->timer); /* Add this entry to the queue. */ qp->prev = NULL; cli(); qp->next = ipqueue; if (qp->next != NULL) qp->next->prev = qp; ipqueue = qp; sti(); return(qp); } /* * 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 != NULL) { 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) { NETDEBUG(printk("Oversized IP packet from %s.\n", in_ntoa(qp->iph->saddr))); ip_statistics.IpReasmFails++; ip_free(qp); return NULL; } if ((skb = dev_alloc_skb(len)) == NULL) { ip_statistics.IpReasmFails++; NETDEBUG(printk("IP: queue_glue: no memory for gluing queue %p\n", qp)); ip_free(qp); return(NULL); } /* Fill in the basic details. */ skb_put(skb,len); skb->h.raw = skb->data; skb->free = 1; /* Copy the original IP headers into the new buffer. */ ptr = (unsigned char *) skb->h.raw; memcpy(ptr, ((unsigned char *) qp->iph), qp->ihlen); ptr += qp->ihlen; count = 0; /* Copy the data portions of all fragments into the new buffer. */ fp = qp->fragments; while(fp != NULL) { if (fp->len < 0 || fp->offset+qp->ihlen+fp->len > skb->len) { NETDEBUG(printk("Invalid fragment list: Fragment over size.\n")); ip_free(qp); kfree_skb(skb,FREE_WRITE); ip_statistics.IpReasmFails++; return NULL; } memcpy((ptr + fp->offset), fp->ptr, fp->len); count += fp->len; fp = fp->next; } skb->pkt_type = qp->fragments->skb->pkt_type; skb->protocol = qp->fragments->skb->protocol; /* We glued together all fragments, so remove the queue entry. */ ip_free(qp); /* Done with all fragments. Fixup the new IP header. */ iph = skb->h.iph; iph->frag_off = 0; iph->tot_len = htons((iph->ihl * 4) + count); skb->ip_hdr = iph; ip_statistics.IpReasmOKs++; return(skb); } /* * Process an incoming IP datagram fragment. */ struct sk_buff *ip_defrag(struct iphdr *iph, struct sk_buff *skb, struct device *dev) { struct ipfrag *prev, *next, *tmp; struct ipfrag *tfp; struct ipq *qp; struct sk_buff *skb2; unsigned char *ptr; int flags, offset; int i, ihl, end; ip_statistics.IpReasmReqds++; /* * Start by cleaning up the memory */ if(ip_frag_mem>IPFRAG_HIGH_THRESH) ip_evictor(); /* * Find the entry of this IP datagram in the "incomplete datagrams" queue. */ qp = ip_find(iph); /* Is this a non-fragmented datagram? */ offset = ntohs(iph->frag_off); flags = offset & ~IP_OFFSET; offset &= IP_OFFSET; if (((flags & IP_MF) == 0) && (offset == 0)) { if (qp != NULL) ip_free(qp); /* Fragmented frame replaced by full unfragmented copy */ return(skb); } offset <<= 3; /* offset is in 8-byte chunks */ ihl = iph->ihl * 4; /* * If the queue already existed, keep restarting its timer as long * as we still are receiving fragments. Otherwise, create a fresh * queue entry. */ if (qp != NULL) { /* ANK. If the first fragment is received, * we should remember the correct IP header (with options) */ if (offset == 0) { qp->ihlen = ihl; memcpy(qp->iph, iph, ihl+8); } del_timer(&qp->timer); qp->timer.expires = jiffies + IP_FRAG_TIME; /* about 30 seconds */ qp->timer.data = (unsigned long) qp; /* pointer to queue */ qp->timer.function = ip_expire; /* expire function */ add_timer(&qp->timer); } else { /* * If we failed to create it, then discard the frame */ if ((qp = ip_create(skb, iph, dev)) == NULL) { skb->sk = NULL; kfree_skb(skb, FREE_READ); ip_statistics.IpReasmFails++; return NULL; } } /* * Attempt to construct an oversize packet. */ if(ntohs(iph->tot_len)+(int)offset>65535) { skb->sk = NULL; NETDEBUG(printk("Oversized packet received from %s\n",in_ntoa(iph->saddr))); kfree_skb(skb, FREE_READ); ip_statistics.IpReasmFails++; return NULL; } /* * Determine the position of this fragment. */ end = offset + ntohs(iph->tot_len) - ihl; /* * Point into the IP datagram 'data' part. */ ptr = skb->data + 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; } /* * 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. * * We never throw the new frag away, so the frag being * dumped has always been charged for. */ 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; next=tfp; /* We have killed the original next frame */ frag_kfree_skb(tmp->skb,FREE_READ); frag_kfree_s(tmp, sizeof(struct ipfrag)); } } /* * Insert this fragment in the chain of fragments. */ tfp = NULL; if(offset<end) tfp = ip_frag_create(offset, end, skb, ptr); /* * No memory to save the fragment - so throw the lot. If we * failed the frag_create we haven't charged the queue. */ if (!tfp) { skb->sk = NULL; kfree_skb(skb, FREE_READ); return NULL; } /* * From now on our buffer is charged to the queues. */ 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)) { skb2 = ip_glue(qp); /* glue together the fragments */ return(skb2); } return(NULL); } /* * This IP datagram is too large to be sent in one piece. Break it up into * smaller pieces (each of size equal to the MAC header plus IP header plus * a block of the data of the original IP data part) that will yet fit in a * single device frame, and queue such a frame for sending by calling the * ip_queue_xmit(). Note that this is recursion, and bad things will happen * if this function causes a loop... * * Yes this is inefficient, feel free to submit a quicker one. * */ void ip_fragment(struct sock *sk, struct sk_buff *skb, struct device *dev, int is_frag) { struct iphdr *iph; unsigned char *raw; unsigned char *ptr; struct sk_buff *skb2; int left, mtu, hlen, len; int offset; unsigned short true_hard_header_len; /* * Point into the IP datagram header. */ raw = skb->data; #if 0 iph = (struct iphdr *) (raw + dev->hard_header_len); skb->ip_hdr = iph; #else iph = skb->ip_hdr; #endif /* * Calculate the length of the link-layer header appended to * the IP-packet. */ true_hard_header_len = ((unsigned char *)iph) - raw; /* * Setup starting values. */ hlen = iph->ihl * 4; left = ntohs(iph->tot_len) - hlen; /* Space per frame */ hlen += true_hard_header_len; mtu = (dev->mtu - hlen); /* Size of data space */ ptr = (raw + hlen); /* Where to start from */ /* * Check for any "DF" flag. [DF means do not fragment] */ if (iph->frag_off & htons(IP_DF)) { ip_statistics.IpFragFails++; NETDEBUG(printk("ip_queue_xmit: frag needed\n")); return; } /* * The protocol doesn't seem to say what to do in the case that the * frame + options doesn't fit the mtu. As it used to fall down dead * in this case we were fortunate it didn't happen */ if(mtu<8) { /* It's wrong but it's better than nothing */ icmp_send(skb,ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED,htons(dev->mtu), dev); ip_statistics.IpFragFails++; return; } /* * Fragment the datagram. */ /* * The initial offset is 0 for a complete frame. When * fragmenting fragments it's wherever this one starts. */ if (is_frag & 2) offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3; else offset = 0; /* * Keep copying data until we run out. */ while(left > 0) { len = left; /* IF: it doesn't fit, use 'mtu' - the data space left */ if (len > mtu) len = mtu; /* IF: we are not sending upto and including the packet end then align the next start on an eight byte boundary */ if (len < left) { len/=8; len*=8; } /* * Allocate buffer. */ if ((skb2 = alloc_skb(len + hlen+15,GFP_ATOMIC)) == NULL) { NETDEBUG(printk("IP: frag: no memory for new fragment!\n")); ip_statistics.IpFragFails++; return; } /* * Set up data on packet */ skb2->arp = skb->arp; skb2->protocol = htons(ETH_P_IP); /* Atleast PPP needs this */ #if 0 if(skb->free==0) printk(KERN_ERR "IP fragmenter: BUG free!=1 in fragmenter\n"); #endif skb2->free = 1; skb_put(skb2,len + hlen); skb2->h.raw=(char *) skb2->data; /* * Charge the memory for the fragment to any owner * it might possess */ if (sk) { atomic_add(skb2->truesize, &sk->wmem_alloc); skb2->sk=sk; } skb2->raddr = skb->raddr; /* For rebuild_header - must be here */ /* * Copy the packet header into the new buffer. */ memcpy(skb2->h.raw, raw, hlen); /* * Copy a block of the IP datagram. */ memcpy(skb2->h.raw + hlen, ptr, len); left -= len; skb2->h.raw+=true_hard_header_len; /* * Fill in the new header fields. */ iph = (struct iphdr *)(skb2->h.raw/*+dev->hard_header_len*/); iph->frag_off = htons((offset >> 3)); skb2->ip_hdr = iph; /* ANK: dirty, but effective trick. Upgrade options only if * the segment to be fragmented was THE FIRST (otherwise, * options are already fixed) and make it ONCE * on the initial skb, so that all the following fragments * will inherit fixed options. */ if (offset == 0) ip_options_fragment(skb); /* * Added AC : If we are fragmenting a fragment that's not the * last fragment then keep MF on each bit */ if (left > 0 || (is_frag & 1)) iph->frag_off |= htons(IP_MF); ptr += len; offset += len; /* * Put this fragment into the sending queue. */ ip_statistics.IpFragCreates++; ip_queue_xmit(sk, dev, skb2, 2); } ip_statistics.IpFragOKs++; }
Go to most recent revision | Compare with Previous | Blame | View Log