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 * Pseudo-driver for the loopback interface.
7 *
8 * Version: @(#)loopback.c 1.0.4b 08/16/93
9 *
10 * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Donald Becker, <becker@cesdis.gsfc.nasa.gov>
13 *
14 * Alan Cox : Fixed oddments for NET3.014
15 * Alan Cox : Rejig for NET3.029 snap #3
16 * Alan Cox : Fixed NET3.029 bugs and sped up
17 * Larry McVoy : Tiny tweak to double performance
18 * Alan Cox : Backed out LMV's tweak - the linux mm
19 * can't take it...
20 * Michael Griffith: Don't bother computing the checksums
21 * on packets received on the loopback
22 * interface.
23 * Alexey Kuznetsov: Potential hang under some extreme
24 * cases removed.
25 *
26 * This program is free software; you can redistribute it and/or
27 * modify it under the terms of the GNU General Public License
28 * as published by the Free Software Foundation; either version
29 * 2 of the License, or (at your option) any later version.
30 */
31 #include <linux/kernel.h>
32 #include <linux/sched.h>
33 #include <linux/interrupt.h>
34 #include <linux/fs.h>
35 #include <linux/types.h>
36 #include <linux/string.h>
37 #include <linux/socket.h>
38 #include <linux/errno.h>
39 #include <linux/fcntl.h>
40 #include <linux/in.h>
41 #include <linux/init.h>
42
43 #include <asm/system.h>
44 #include <asm/uaccess.h>
45 #include <asm/io.h>
46
47 #include <linux/inet.h>
48 #include <linux/netdevice.h>
49 #include <linux/etherdevice.h>
50 #include <linux/skbuff.h>
51 #include <net/sock.h>
52 #include <linux/if_ether.h> /* For the statistics structure. */
53 #include <linux/if_arp.h> /* For ARPHRD_ETHER */
54
55 #define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16)
56
57 /*
58 * The higher levels take care of making this non-reentrant (it's
59 * called with bh's disabled).
60 */
61 static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)
62 {
63 struct net_device_stats *stats = (struct net_device_stats *)dev->priv;
64
65 /*
66 * Optimise so buffers with skb->free=1 are not copied but
67 * instead are lobbed from tx queue to rx queue
68 */
69
70 if(atomic_read(&skb->users) != 1)
71 {
72 struct sk_buff *skb2=skb;
73 skb=skb_clone(skb, GFP_ATOMIC); /* Clone the buffer */
74 if(skb==NULL) {
75 kfree_skb(skb2);
76 return 0;
77 }
78 kfree_skb(skb2);
79 }
80 else
81 skb_orphan(skb);
82
83 skb->protocol=eth_type_trans(skb,dev);
84 skb->dev=dev;
85 #ifndef LOOPBACK_MUST_CHECKSUM
86 skb->ip_summed = CHECKSUM_UNNECESSARY;
87 #endif
88 netif_rx(skb);
89
90 stats->rx_bytes+=skb->len;
91 stats->tx_bytes+=skb->len;
92 stats->rx_packets++;
93 stats->tx_packets++;
94
95 return(0);
96 }
97
98 static struct net_device_stats *get_stats(struct net_device *dev)
99 {
100 return (struct net_device_stats *)dev->priv;
101 }
102
103 /* Initialize the rest of the LOOPBACK device. */
104 int __init loopback_init(struct net_device *dev)
105 {
106 dev->mtu = PAGE_SIZE - LOOPBACK_OVERHEAD;
107 dev->hard_start_xmit = loopback_xmit;
108 dev->hard_header = eth_header;
109 dev->hard_header_cache = eth_header_cache;
110 dev->header_cache_update= eth_header_cache_update;
111 dev->hard_header_len = ETH_HLEN; /* 14 */
112 dev->addr_len = ETH_ALEN; /* 6 */
113 dev->tx_queue_len = 0;
114 dev->type = ARPHRD_LOOPBACK; /* 0x0001 */
115 dev->rebuild_header = eth_rebuild_header;
116 dev->flags = IFF_LOOPBACK;
117 dev->priv = kmalloc(sizeof(struct net_device_stats), GFP_KERNEL);
118 if (dev->priv == NULL)
119 return -ENOMEM;
120 memset(dev->priv, 0, sizeof(struct net_device_stats));
121 dev->get_stats = get_stats;
122
123 if (num_physpages >= ((128*1024*1024)>>PAGE_SHIFT))
124 dev->mtu = 4096*4 - LOOPBACK_OVERHEAD;
125
126 /*
127 * Fill in the generic fields of the device structure.
128 */
129
130 dev_init_buffers(dev);
131
132 return(0);
133 };
134
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