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  *
  30  *              This program is free software; you can redistribute it and/or
  31  *              modify it under the terms of the GNU General Public License
  32  *              as published by the Free Software Foundation; either version
  33  *              2 of the License, or (at your option) any later version.
  34  */
  35 #include <asm/segment.h>
  36 #include <asm/system.h>
  37 #include <linux/types.h>
  38 #include <linux/kernel.h>
  39 #include <linux/sched.h>
  40 #include <linux/string.h>
  41 #include <linux/mm.h>
  42 #include <linux/socket.h>
  43 #include <linux/in.h>
  44 #include <linux/inet.h>
  45 #include <linux/netdevice.h>
  46 #include <linux/etherdevice.h>
  47 #include <linux/skbuff.h>
  48 #include <linux/errno.h>
  49 #include <linux/config.h>
  50 #include <net/arp.h>
  51 #include <net/sock.h>
  52 #include <asm/checksum.h>
  53 
  54 void eth_setup(char *str, int *ints)
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  55 {
  56         struct device *d = dev_base;
  57 
  58         if (!str || !*str)
  59                 return;
  60         while (d) 
  61         {
  62                 if (!strcmp(str,d->name)) 
  63                 {
  64                         if (ints[0] > 0)
  65                                 d->irq=ints[1];
  66                         if (ints[0] > 1)
  67                                 d->base_addr=ints[2];
  68                         if (ints[0] > 2)
  69                                 d->mem_start=ints[3];
  70                         if (ints[0] > 3)
  71                                 d->mem_end=ints[4];
  72                         break;
  73                 }
  74                 d=d->next;
  75         }
  76 }
  77 
  78 
  79 /*
  80  *       Create the Ethernet MAC header for an arbitrary protocol layer 
  81  *
  82  *      saddr=NULL      means use device source address
  83  *      daddr=NULL      means leave destination address (eg unresolved arp)
  84  */
  85 
  86 int eth_header(struct sk_buff *skb, struct device *dev, unsigned short type,
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  87            void *daddr, void *saddr, unsigned len)
  88 {
  89         struct ethhdr *eth = (struct ethhdr *)skb_push(skb,14);
  90 
  91         /* 
  92          *      Set the protocol type. For a packet of type ETH_P_802_3 we put the length
  93          *      in here instead. It is up to the 802.2 layer to carry protocol information.
  94          */
  95         
  96         if(type!=ETH_P_802_3) 
  97                 eth->h_proto = htons(type);
  98         else
  99                 eth->h_proto = htons(len);
 100 
 101         /*
 102          *      Set the source hardware address. 
 103          */
 104          
 105         if(saddr)
 106                 memcpy(eth->h_source,saddr,dev->addr_len);
 107         else
 108                 memcpy(eth->h_source,dev->dev_addr,dev->addr_len);
 109 
 110         /*
 111          *      Anyway, the loopback-device should never use this function... 
 112          */
 113 
 114         if (dev->flags & IFF_LOOPBACK) 
 115         {
 116                 memset(eth->h_dest, 0, dev->addr_len);
 117                 return(dev->hard_header_len);
 118         }
 119         
 120         if(daddr)
 121         {
 122                 memcpy(eth->h_dest,daddr,dev->addr_len);
 123                 return dev->hard_header_len;
 124         }
 125         
 126         return -dev->hard_header_len;
 127 }
 128 
 129 
 130 /*
 131  *      Rebuild the Ethernet MAC header. This is called after an ARP
 132  *      (or in future other address resolution) has completed on this
 133  *      sk_buff. We now let ARP fill in the other fields.
 134  */
 135  
 136 int eth_rebuild_header(void *buff, struct device *dev, unsigned long dst,
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 137                         struct sk_buff *skb)
 138 {
 139         struct ethhdr *eth = (struct ethhdr *)buff;
 140 
 141         /*
 142          *      Only ARP/IP is currently supported
 143          */
 144          
 145         if(eth->h_proto != htons(ETH_P_IP)) 
 146         {
 147                 printk("eth_rebuild_header: Don't know how to resolve type %d addresses?\n",(int)eth->h_proto);
 148                 memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
 149                 return 0;
 150         }
 151 
 152         /*
 153          *      Try and get ARP to resolve the header.
 154          */
 155 #ifdef CONFIG_INET       
 156         return arp_find(eth->h_dest, dst, dev, dev->pa_addr, skb)? 1 : 0;
 157 #else
 158         return 0;       
 159 #endif  
 160 }
 161 
 162 
 163 /*
 164  *      Determine the packet's protocol ID. The rule here is that we 
 165  *      assume 802.3 if the type field is short enough to be a length.
 166  *      This is normal practice and works for any 'now in use' protocol.
 167  */
 168  
 169 unsigned short eth_type_trans(struct sk_buff *skb, struct device *dev)
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 170 {
 171         struct ethhdr *eth;
 172         unsigned char *rawp;
 173         
 174         skb->mac.raw=skb->data;
 175         skb_pull(skb,14);       
 176         eth= skb->mac.ethernet;
 177         
 178         if(*eth->h_dest&1)
 179         {
 180                 if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)
 181                         skb->pkt_type=PACKET_BROADCAST;
 182                 else
 183                         skb->pkt_type=PACKET_MULTICAST;
 184         }
 185         
 186         else if(dev->flags&IFF_PROMISC)
 187         {
 188                 if(memcmp(eth->h_dest,dev->dev_addr, ETH_ALEN))
 189                         skb->pkt_type=PACKET_OTHERHOST;
 190         }
 191         
 192         if (ntohs(eth->h_proto) >= 1536)
 193                 return eth->h_proto;
 194                 
 195         rawp = skb->data;
 196         
 197         /*
 198          *      This is a magic hack to spot IPX packets. Older Novell breaks
 199          *      the protocol design and runs IPX over 802.3 without an 802.2 LLC
 200          *      layer. We look for FFFF which isnt a used 802.2 SSAP/DSAP. This
 201          *      won't work for fault tolerant netware but does for the rest.
 202          */
 203         if (*(unsigned short *)rawp == 0xFFFF)
 204                 return htons(ETH_P_802_3);
 205                 
 206         /*
 207          *      Real 802.2 LLC
 208          */
 209         return htons(ETH_P_802_2);
 210 }
 211 
 212 /*
 213  *      Header caching for ethernet. Try to find and cache a header to avoid arp overhead.
 214  */
 215  
 216 void eth_header_cache(struct device *dev, struct sock *sk, unsigned long saddr, unsigned long daddr)
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 217 {
 218         int v=arp_find_cache(sk->ip_hcache_data, daddr, dev);
 219         if(v!=1)
 220                 sk->ip_hcache_state=0;  /* Try when arp resolves */
 221         else
 222         {
 223                 memcpy(sk->ip_hcache_data+6, dev->dev_addr, ETH_ALEN);
 224                 sk->ip_hcache_data[12]=ETH_P_IP>>8;
 225                 sk->ip_hcache_data[13]=ETH_P_IP&0xFF;
 226                 sk->ip_hcache_state=1;
 227                 sk->ip_hcache_stamp=arp_cache_stamp;
 228                 sk->ip_hcache_ver=&arp_cache_stamp;
 229         }
 230 }
 231 
 232 /*
 233  *      Copy from an ethernet device memory space to an sk_buff while checksumming if IP
 234  */
 235  
 236 void eth_copy_and_sum(struct sk_buff *dest, unsigned char *src, int length, int base)
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 237 {
 238         struct ethhdr *eth;
 239 
 240         IS_SKB(dest);
 241         eth=(struct ethhdr *)dest->data;
 242         memcpy(dest->data,src,34);      /* ethernet is always >= 60 */
 243         length-=34;
 244         if(eth->h_proto!=htons(ETH_P_IP))
 245         {
 246                 memcpy(dest->data+34,src+34,length);
 247                 return;
 248         }
 249         dest->csum=csum_partial_copy(src+34,dest->data+34,length,base);
 250         dest->ip_summed=1;
 251 }

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