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  *
  31  *              This program is free software; you can redistribute it and/or
  32  *              modify it under the terms of the GNU General Public License
  33  *              as published by the Free Software Foundation; either version
  34  *              2 of the License, or (at your option) any later version.
  35  */
  36 #include <asm/segment.h>
  37 #include <asm/system.h>
  38 #include <linux/types.h>
  39 #include <linux/kernel.h>
  40 #include <linux/sched.h>
  41 #include <linux/string.h>
  42 #include <linux/mm.h>
  43 #include <linux/socket.h>
  44 #include <linux/in.h>
  45 #include <linux/inet.h>
  46 #include <linux/netdevice.h>
  47 #include <linux/etherdevice.h>
  48 #include <linux/skbuff.h>
  49 #include <linux/errno.h>
  50 #include <linux/config.h>
  51 #include <net/arp.h>
  52 #include <net/sock.h>
  53 #include <asm/checksum.h>
  54 
  55 void eth_setup(char *str, int *ints)
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  56 {
  57         struct device *d = dev_base;
  58 
  59         if (!str || !*str)
  60                 return;
  61         while (d) 
  62         {
  63                 if (!strcmp(str,d->name)) 
  64                 {
  65                         if (ints[0] > 0)
  66                                 d->irq=ints[1];
  67                         if (ints[0] > 1)
  68                                 d->base_addr=ints[2];
  69                         if (ints[0] > 2)
  70                                 d->mem_start=ints[3];
  71                         if (ints[0] > 3)
  72                                 d->mem_end=ints[4];
  73                         break;
  74                 }
  75                 d=d->next;
  76         }
  77 }
  78 
  79 
  80 /*
  81  *       Create the Ethernet MAC header for an arbitrary protocol layer 
  82  *
  83  *      saddr=NULL      means use device source address
  84  *      daddr=NULL      means leave destination address (eg unresolved arp)
  85  */
  86 
  87 int eth_header(struct sk_buff *skb, struct device *dev, unsigned short type,
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  88            void *daddr, void *saddr, unsigned len)
  89 {
  90         struct ethhdr *eth = (struct ethhdr *)skb_push(skb,14);
  91 
  92         /* 
  93          *      Set the protocol type. For a packet of type ETH_P_802_3 we put the length
  94          *      in here instead. It is up to the 802.2 layer to carry protocol information.
  95          */
  96         
  97         if(type!=ETH_P_802_3) 
  98                 eth->h_proto = htons(type);
  99         else
 100                 eth->h_proto = htons(len);
 101 
 102         /*
 103          *      Set the source hardware address. 
 104          */
 105          
 106         if(saddr)
 107                 memcpy(eth->h_source,saddr,dev->addr_len);
 108         else
 109                 memcpy(eth->h_source,dev->dev_addr,dev->addr_len);
 110 
 111         /*
 112          *      Anyway, the loopback-device should never use this function... 
 113          */
 114 
 115         if (dev->flags & IFF_LOOPBACK) 
 116         {
 117                 memset(eth->h_dest, 0, dev->addr_len);
 118                 return(dev->hard_header_len);
 119         }
 120         
 121         if(daddr)
 122         {
 123                 memcpy(eth->h_dest,daddr,dev->addr_len);
 124                 return dev->hard_header_len;
 125         }
 126         
 127         return -dev->hard_header_len;
 128 }
 129 
 130 
 131 /*
 132  *      Rebuild the Ethernet MAC header. This is called after an ARP
 133  *      (or in future other address resolution) has completed on this
 134  *      sk_buff. We now let ARP fill in the other fields.
 135  */
 136  
 137 int eth_rebuild_header(void *buff, struct device *dev, unsigned long dst,
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 138                         struct sk_buff *skb)
 139 {
 140         struct ethhdr *eth = (struct ethhdr *)buff;
 141 
 142         /*
 143          *      Only ARP/IP is currently supported
 144          */
 145          
 146         if(eth->h_proto != htons(ETH_P_IP)) 
 147         {
 148                 printk("eth_rebuild_header: Don't know how to resolve type %d addresses?\n",(int)eth->h_proto);
 149                 memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
 150                 return 0;
 151         }
 152 
 153         /*
 154          *      Try and get ARP to resolve the header.
 155          */
 156 #ifdef CONFIG_INET       
 157         return arp_find(eth->h_dest, dst, dev, dev->pa_addr, skb)? 1 : 0;
 158 #else
 159         return 0;       
 160 #endif  
 161 }
 162 
 163 
 164 /*
 165  *      Determine the packet's protocol ID. The rule here is that we 
 166  *      assume 802.3 if the type field is short enough to be a length.
 167  *      This is normal practice and works for any 'now in use' protocol.
 168  */
 169  
 170 unsigned short eth_type_trans(struct sk_buff *skb, struct device *dev)
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 171 {
 172         struct ethhdr *eth;
 173         unsigned char *rawp;
 174         
 175         skb->mac.raw=skb->data;
 176         skb_pull(skb,14);       
 177         eth= skb->mac.ethernet;
 178         
 179         if(*eth->h_dest&1)
 180         {
 181                 if(memcmp(eth->h_dest,dev->broadcast, ETH_ALEN)==0)
 182                         skb->pkt_type=PACKET_BROADCAST;
 183                 else
 184                         skb->pkt_type=PACKET_MULTICAST;
 185         }
 186         
 187         else if(dev->flags&IFF_PROMISC)
 188         {
 189                 if(memcmp(eth->h_dest,dev->dev_addr, ETH_ALEN))
 190                         skb->pkt_type=PACKET_OTHERHOST;
 191         }
 192         
 193         if (ntohs(eth->h_proto) >= 1536)
 194                 return eth->h_proto;
 195                 
 196         rawp = skb->data;
 197         
 198         /*
 199          *      This is a magic hack to spot IPX packets. Older Novell breaks
 200          *      the protocol design and runs IPX over 802.3 without an 802.2 LLC
 201          *      layer. We look for FFFF which isnt a used 802.2 SSAP/DSAP. This
 202          *      won't work for fault tolerant netware but does for the rest.
 203          */
 204         if (*(unsigned short *)rawp == 0xFFFF)
 205                 return htons(ETH_P_802_3);
 206                 
 207         /*
 208          *      Real 802.2 LLC
 209          */
 210         return htons(ETH_P_802_2);
 211 }
 212 
 213 /*
 214  *      Header caching for ethernet. Try to find and cache a header to avoid arp overhead.
 215  */
 216  
 217 void eth_header_cache(struct device *dev, struct sock *sk, unsigned long saddr, unsigned long daddr)
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 218 {
 219         int v=arp_find_cache(sk->ip_hcache_data, daddr, dev);
 220         if(v!=1)
 221                 sk->ip_hcache_state=0;  /* Try when arp resolves */
 222         else
 223         {
 224                 memcpy(sk->ip_hcache_data+6, dev->dev_addr, ETH_ALEN);
 225                 sk->ip_hcache_data[12]=ETH_P_IP>>8;
 226                 sk->ip_hcache_data[13]=ETH_P_IP&0xFF;
 227                 sk->ip_hcache_state=1;
 228                 sk->ip_hcache_stamp=arp_cache_stamp;
 229                 sk->ip_hcache_ver=&arp_cache_stamp;
 230         }
 231 }
 232 
 233 /*
 234  *      Copy from an ethernet device memory space to an sk_buff while checksumming if IP
 235  *      The magic "34" is Rx_addr+Tx_addr+type_field+sizeof(struct iphdr) == 6+6+2+20.
 236  */
 237  
 238 void eth_copy_and_sum(struct sk_buff *dest, unsigned char *src, int length, int base)
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 239 {
 240         struct ethhdr *eth;
 241         struct iphdr *iph;
 242 
 243         IS_SKB(dest);
 244         eth=(struct ethhdr *)dest->data;
 245         memcpy(dest->data,src,34);      /* ethernet is always >= 60 */
 246         length-=34;
 247         if(eth->h_proto!=htons(ETH_P_IP))
 248         {
 249                 memcpy(dest->data+34,src+34,length);
 250                 return;
 251         }
 252         /*
 253          * We have to watch for padded packets. The csum doesn't include the
 254          * padding, and there is no point in copying the padding anyway.
 255          */
 256         iph=(struct iphdr*)(src+14);    /* 14 = Rx_addr+Tx_addr+type_field */
 257         if (ntohs(iph->tot_len)-sizeof(struct iphdr) <= length)
 258                 length=ntohs(iph->tot_len)-sizeof(struct iphdr);
 259 
 260         dest->csum=csum_partial_copy(src+34,dest->data+34,length,base);
 261         dest->ip_summed=1;
 262 }

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