/* * 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. * * Pseudo-driver for the loopback interface. * * Version: @(#)loopback.c 1.0.4b 08/16/93 * * Authors: Ross Biro * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> * Donald Becker, <becker@scyld.com> * * Alan Cox : Fixed oddments for NET3.014 * Alan Cox : Rejig for NET3.029 snap #3 * Alan Cox : Fixed NET3.029 bugs and sped up * Larry McVoy : Tiny tweak to double performance * Alan Cox : Backed out LMV's tweak - the linux mm * can't take it... * Michael Griffith: Don't bother computing the checksums * on packets received on the loopback * interface. * Alexey Kuznetsov: Potential hang under some extreme * cases removed. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include <linux/kernel.h> #include <linux/jiffies.h> #include <linux/module.h> #include <linux/interrupt.h> #include <linux/fs.h> #include <linux/types.h> #include <linux/string.h> #include <linux/socket.h> #include <linux/errno.h> #include <linux/fcntl.h> #include <linux/in.h> #include <linux/init.h> #include <asm/system.h> #include <asm/uaccess.h> #include <asm/io.h> #include <linux/inet.h> #include <linux/netdevice.h> #include <linux/etherdevice.h> #include <linux/skbuff.h> #include <linux/ethtool.h> #include <net/sock.h> #include <net/checksum.h> #include <linux/if_ether.h> /* For the statistics structure. */ #include <linux/if_arp.h> /* For ARPHRD_ETHER */ #include <linux/ip.h> #include <linux/tcp.h> #include <linux/percpu.h> struct pcpu_lstats { unsigned long packets; unsigned long bytes; }; static DEFINE_PER_CPU(struct pcpu_lstats, pcpu_lstats); #define LOOPBACK_OVERHEAD (128 + MAX_HEADER + 16 + 16) /* KISS: just allocate small chunks and copy bits. * * So, in fact, this is documentation, explaining what we expect * of largesending device modulo TCP checksum, which is ignored for loopback. */ #ifdef LOOPBACK_TSO static void emulate_large_send_offload(struct sk_buff *skb) { struct iphdr *iph = ip_hdr(skb); struct tcphdr *th = (struct tcphdr *)(skb_network_header(skb) + (iph->ihl * 4)); unsigned int doffset = (iph->ihl + th->doff) * 4; unsigned int mtu = skb_shinfo(skb)->gso_size + doffset; unsigned int offset = 0; u32 seq = ntohl(th->seq); u16 id = ntohs(iph->id); while (offset + doffset < skb->len) { unsigned int frag_size = min(mtu, skb->len - offset) - doffset; struct sk_buff *nskb = alloc_skb(mtu + 32, GFP_ATOMIC); if (!nskb) break; skb_reserve(nskb, 32); skb_set_mac_header(nskb, -ETH_HLEN); skb_reset_network_header(nskb); iph = ip_hdr(nskb); skb_copy_to_linear_data(nskb, skb_network_header(skb), doffset); if (skb_copy_bits(skb, doffset + offset, nskb->data + doffset, frag_size)) BUG(); skb_put(nskb, doffset + frag_size); nskb->ip_summed = CHECKSUM_UNNECESSARY; nskb->dev = skb->dev; nskb->priority = skb->priority; nskb->protocol = skb->protocol; nskb->dst = dst_clone(skb->dst); memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); nskb->pkt_type = skb->pkt_type; th = (struct tcphdr *)(skb_network_header(nskb) + iph->ihl * 4); iph->tot_len = htons(frag_size + doffset); iph->id = htons(id); iph->check = 0; iph->check = ip_fast_csum((unsigned char *) iph, iph->ihl); th->seq = htonl(seq); if (offset + doffset + frag_size < skb->len) th->fin = th->psh = 0; netif_rx(nskb); offset += frag_size; seq += frag_size; id++; } dev_kfree_skb(skb); } #endif /* LOOPBACK_TSO */ /* * The higher levels take care of making this non-reentrant (it's * called with bh's disabled). */ static int loopback_xmit(struct sk_buff *skb, struct net_device *dev) { struct pcpu_lstats *lb_stats; skb_orphan(skb); skb->protocol = eth_type_trans(skb,dev); #ifndef LOOPBACK_MUST_CHECKSUM skb->ip_summed = CHECKSUM_UNNECESSARY; #endif #ifdef LOOPBACK_TSO if (skb_is_gso(skb)) { BUG_ON(skb->protocol != htons(ETH_P_IP)); BUG_ON(ip_hdr(skb)->protocol != IPPROTO_TCP); emulate_large_send_offload(skb); return 0; } #endif dev->last_rx = jiffies; /* it's OK to use __get_cpu_var() because BHs are off */ lb_stats = &__get_cpu_var(pcpu_lstats); lb_stats->bytes += skb->len; lb_stats->packets++; netif_rx(skb); return 0; } static struct net_device_stats *get_stats(struct net_device *dev) { struct net_device_stats *stats = &dev->stats; unsigned long bytes = 0; unsigned long packets = 0; int i; for_each_possible_cpu(i) { const struct pcpu_lstats *lb_stats; lb_stats = &per_cpu(pcpu_lstats, i); bytes += lb_stats->bytes; packets += lb_stats->packets; } stats->rx_packets = packets; stats->tx_packets = packets; stats->rx_bytes = bytes; stats->tx_bytes = bytes; return stats; } static u32 always_on(struct net_device *dev) { return 1; } static const struct ethtool_ops loopback_ethtool_ops = { .get_link = always_on, .get_tso = ethtool_op_get_tso, .set_tso = ethtool_op_set_tso, .get_tx_csum = always_on, .get_sg = always_on, .get_rx_csum = always_on, }; /* * The loopback device is special. There is only one instance and * it is statically allocated. Don't do this for other devices. */ struct net_device loopback_dev = { .name = "lo", .get_stats = &get_stats, .mtu = (16 * 1024) + 20 + 20 + 12, .hard_start_xmit = loopback_xmit, .hard_header = eth_header, .hard_header_cache = eth_header_cache, .header_cache_update = eth_header_cache_update, .hard_header_len = ETH_HLEN, /* 14 */ .addr_len = ETH_ALEN, /* 6 */ .tx_queue_len = 0, .type = ARPHRD_LOOPBACK, /* 0x0001*/ .rebuild_header = eth_rebuild_header, .flags = IFF_LOOPBACK, .features = NETIF_F_SG | NETIF_F_FRAGLIST #ifdef LOOPBACK_TSO | NETIF_F_TSO #endif | NETIF_F_NO_CSUM | NETIF_F_HIGHDMA | NETIF_F_LLTX | NETIF_F_NETNS_LOCAL, .ethtool_ops = &loopback_ethtool_ops, .nd_net = &init_net, }; /* Setup and register the loopback device. */ static int __init loopback_init(void) { int err = register_netdev(&loopback_dev); if (err) panic("loopback: Failed to register netdevice: %d\n", err); return err; }; module_init(loopback_init); EXPORT_SYMBOL(loopback_dev);