root/net/ethernet/eth.c

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DEFINITIONS

This source file includes following definitions.
  1. eth_setup
  2. eth_header
  3. eth_rebuild_header
  4. eth_type_trans
  5. eth_header_cache
  6. eth_copy_and_sum

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Ethernet-type device handling.
   7  *
   8  * Version:     @(#)eth.c       1.0.7   05/25/93
   9  *
  10  * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
  11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  *              Mark Evans, <evansmp@uhura.aston.ac.uk>
  13  *              Florian  La Roche, <rzsfl@rz.uni-sb.de>
  14  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
  15  * 
  16  * Fixes:
  17  *              Mr Linux        : Arp problems
  18  *              Alan Cox        : Generic queue tidyup (very tiny here)
  19  *              Alan Cox        : eth_header ntohs should be htons
  20  *              Alan Cox        : eth_rebuild_header missing an htons and
  21  *                                minor other things.
  22  *              Tegge           : Arp bug fixes. 
  23  *              Florian         : Removed many unnecessary functions, code cleanup
  24  *                                and changes for new arp and skbuff.
  25  *              Alan Cox        : Redid header building to reflect new format.
  26  *              Alan Cox        : ARP only when compiled with CONFIG_INET
  27  *              Greg Page       : 802.2 and SNAP stuff.
  28  *              Alan Cox        : MAC layer pointers/new format.
  29  *              Paul Gortmaker  : eth_copy_and_sum shouldn't csum padding.
  30  *              Alan Cox        : Protect against forwarding explosions with
  31  *                                older network drivers and IFF_ALLMULTI
  32  *
  33  *              This program is free software; you can redistribute it and/or
  34  *              modify it under the terms of the GNU General Public License
  35  *              as published by the Free Software Foundation; either version
  36  *              2 of the License, or (at your option) any later version.
  37  */
  38 #include <asm/segment.h>
  39 #include <asm/system.h>
  40 #include <linux/types.h>
  41 #include <linux/kernel.h>
  42 #include <linux/sched.h>
  43 #include <linux/string.h>
  44 #include <linux/mm.h>
  45 #include <linux/socket.h>
  46 #include <linux/in.h>
  47 #include <linux/inet.h>
  48 #include <linux/netdevice.h>
  49 #include <linux/etherdevice.h>
  50 #include <linux/skbuff.h>
  51 #include <linux/errno.h>
  52 #include <linux/config.h>
  53 #include <net/arp.h>
  54 #include <net/sock.h>
  55 #include <asm/checksum.h>
  56 
  57 void eth_setup(char *str, int *ints)
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  58 {
  59         struct device *d = dev_base;
  60 
  61         if (!str || !*str)
  62                 return;
  63         while (d) 
  64         {
  65                 if (!strcmp(str,d->name)) 
  66                 {
  67                         if (ints[0] > 0)
  68                                 d->irq=ints[1];
  69                         if (ints[0] > 1)
  70                                 d->base_addr=ints[2];
  71                         if (ints[0] > 2)
  72                                 d->mem_start=ints[3];
  73                         if (ints[0] > 3)
  74                                 d->mem_end=ints[4];
  75                         break;
  76                 }
  77                 d=d->next;
  78         }
  79 }
  80 
  81 
  82 /*
  83  *       Create the Ethernet MAC header for an arbitrary protocol layer 
  84  *
  85  *      saddr=NULL      means use device source address
  86  *      daddr=NULL      means leave destination address (eg unresolved arp)
  87  */
  88 
  89 int eth_header(struct sk_buff *skb, struct device *dev, unsigned short type,
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  90            void *daddr, void *saddr, unsigned len)
  91 {
  92         struct ethhdr *eth = (struct ethhdr *)skb_push(skb,14);
  93 
  94         /* 
  95          *      Set the protocol type. For a packet of type ETH_P_802_3 we put the length
  96          *      in here instead. It is up to the 802.2 layer to carry protocol information.
  97          */
  98         
  99         if(type!=ETH_P_802_3) 
 100                 eth->h_proto = htons(type);
 101         else
 102                 eth->h_proto = htons(len);
 103 
 104         /*
 105          *      Set the source hardware address. 
 106          */
 107          
 108         if(saddr)
 109                 memcpy(eth->h_source,saddr,dev->addr_len);
 110         else
 111                 memcpy(eth->h_source,dev->dev_addr,dev->addr_len);
 112 
 113         /*
 114          *      Anyway, the loopback-device should never use this function... 
 115          */
 116 
 117         if (dev->flags & IFF_LOOPBACK) 
 118         {
 119                 memset(eth->h_dest, 0, dev->addr_len);
 120                 return(dev->hard_header_len);
 121         }
 122         
 123         if(daddr)
 124         {
 125                 memcpy(eth->h_dest,daddr,dev->addr_len);
 126                 return dev->hard_header_len;
 127         }
 128         
 129         return -dev->hard_header_len;
 130 }
 131 
 132 
 133 /*
 134  *      Rebuild the Ethernet MAC header. This is called after an ARP
 135  *      (or in future other address resolution) has completed on this
 136  *      sk_buff. We now let ARP fill in the other fields.
 137  */
 138  
 139 int eth_rebuild_header(void *buff, struct device *dev, unsigned long dst,
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 140                         struct sk_buff *skb)
 141 {
 142         struct ethhdr *eth = (struct ethhdr *)buff;
 143 
 144         /*
 145          *      Only ARP/IP is currently supported
 146          */
 147          
 148         if(eth->h_proto != htons(ETH_P_IP)) 
 149         {
 150                 printk("eth_rebuild_header: Don't know how to resolve type %d addresses?\n",(int)eth->h_proto);
 151                 memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
 152                 return 0;
 153         }
 154 
 155         /*
 156          *      Try and get ARP to resolve the header.
 157          */
 158 #ifdef CONFIG_INET       
 159         return arp_find(eth->h_dest, dst, dev, dev->pa_addr, skb)? 1 : 0;
 160 #else
 161         return 0;       
 162 #endif  
 163 }
 164 
 165 
 166 /*
 167  *      Determine the packet's protocol ID. The rule here is that we 
 168  *      assume 802.3 if the type field is short enough to be a length.
 169  *      This is normal practice and works for any 'now in use' protocol.
 170  */
 171  
 172 unsigned short eth_type_trans(struct sk_buff *skb, struct device *dev)
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 173 {
 174         struct ethhdr *eth;
 175         unsigned char *rawp;
 176         
 177         skb->mac.raw=skb->data;
 178         skb_pull(skb,14);       
 179         eth= skb->mac.ethernet;
 180         
 181         if(*eth->h_dest&1)
 182         {
 183                 if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)
 184                         skb->pkt_type=PACKET_BROADCAST;
 185                 else
 186                         skb->pkt_type=PACKET_MULTICAST;
 187         }
 188         
 189         /*
 190          *      This ALLMULTI check should be redundant by 1.4
 191          *      so don't forget to remove it.
 192          */
 193          
 194         else if(dev->flags&(IFF_PROMISC|IFF_ALLMULTI))
 195         {
 196                 if(memcmp(eth->h_dest,dev->dev_addr, ETH_ALEN))
 197                         skb->pkt_type=PACKET_OTHERHOST;
 198         }
 199         
 200         if (ntohs(eth->h_proto) >= 1536)
 201                 return eth->h_proto;
 202                 
 203         rawp = skb->data;
 204         
 205         /*
 206          *      This is a magic hack to spot IPX packets. Older Novell breaks
 207          *      the protocol design and runs IPX over 802.3 without an 802.2 LLC
 208          *      layer. We look for FFFF which isnt a used 802.2 SSAP/DSAP. This
 209          *      won't work for fault tolerant netware but does for the rest.
 210          */
 211         if (*(unsigned short *)rawp == 0xFFFF)
 212                 return htons(ETH_P_802_3);
 213                 
 214         /*
 215          *      Real 802.2 LLC
 216          */
 217         return htons(ETH_P_802_2);
 218 }
 219 
 220 /*
 221  *      Header caching for ethernet. Try to find and cache a header to avoid arp overhead.
 222  */
 223  
 224 void eth_header_cache(struct device *dev, struct sock *sk, unsigned long saddr, unsigned long daddr)
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 225 {
 226         int v=arp_find_cache(sk->ip_hcache_data, daddr, dev);
 227         if(v!=1)
 228                 sk->ip_hcache_state=0;  /* Try when arp resolves */
 229         else
 230         {
 231                 memcpy(sk->ip_hcache_data+6, dev->dev_addr, ETH_ALEN);
 232                 sk->ip_hcache_data[12]=ETH_P_IP>>8;
 233                 sk->ip_hcache_data[13]=ETH_P_IP&0xFF;
 234                 sk->ip_hcache_state=1;
 235                 sk->ip_hcache_stamp=arp_cache_stamp;
 236                 sk->ip_hcache_ver=&arp_cache_stamp;
 237         }
 238 }
 239 
 240 /*
 241  *      Copy from an ethernet device memory space to an sk_buff while checksumming if IP
 242  *      The magic "34" is Rx_addr+Tx_addr+type_field+sizeof(struct iphdr) == 6+6+2+20.
 243  */
 244  
 245 void eth_copy_and_sum(struct sk_buff *dest, unsigned char *src, int length, int base)
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 246 {
 247         struct ethhdr *eth;
 248         struct iphdr *iph;
 249         int ip_length;
 250 
 251         IS_SKB(dest);
 252         eth=(struct ethhdr *)dest->data;
 253         if(eth->h_proto!=htons(ETH_P_IP))
 254         {
 255                 memcpy(dest->data,src,length);
 256                 return;
 257         }
 258         /*
 259          * We have to watch for padded packets. The csum doesn't include the
 260          * padding, and there is no point in copying the padding anyway.
 261          * We have to use the smaller of length and ip_length because it
 262          * can happen that ip_length > length.
 263          */
 264         memcpy(dest->data,src,34);      /* ethernet is always >= 34 */
 265         length -= 34;
 266         iph=(struct iphdr*)(src+14);    /* 14 = Rx_addr+Tx_addr+type_field */
 267         ip_length = ntohs(iph->tot_len) - sizeof(struct iphdr);
 268         if (ip_length <= length)
 269                 length=ip_length;
 270 
 271         dest->csum=csum_partial_copy(src+34,dest->data+34,length,base);
 272         dest->ip_summed=1;
 273 }

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