/*D:500 * The Guest network driver. * * This is very simple a virtual network driver, and our last Guest driver. * The only trick is that it can talk directly to multiple other recipients * (ie. other Guests on the same network). It can also be used with only the * Host on the network. :*/ /* Copyright 2006 Rusty Russell IBM Corporation * * 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. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ //#define DEBUG #include #include #include #include #include #include #define SHARED_SIZE PAGE_SIZE #define MAX_LANS 4 #define NUM_SKBS 8 /*D:530 The "struct lguestnet_info" contains all the information we need to * know about the network device. */ struct lguestnet_info { /* The mapped device page(s) (an array of "struct lguest_net"). */ struct lguest_net *peer; /* The physical address of the device page(s) */ unsigned long peer_phys; /* The size of the device page(s). */ unsigned long mapsize; /* The lguest_device I come from */ struct lguest_device *lgdev; /* My peerid (ie. my slot in the array). */ unsigned int me; /* Receive queue: the network packets waiting to be filled. */ struct sk_buff *skb[NUM_SKBS]; struct lguest_dma dma[NUM_SKBS]; }; /*:*/ /* How many bytes left in this page. */ static unsigned int rest_of_page(void *data) { return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE); } /*D:570 Each peer (ie. Guest or Host) on the network binds their receive * buffers to a different key: we simply use the physical address of the * device's memory page plus the peer number. The Host insists that all keys * be a multiple of 4, so we multiply the peer number by 4. */ static unsigned long peer_key(struct lguestnet_info *info, unsigned peernum) { return info->peer_phys + 4 * peernum; } /* This is the routine which sets up a "struct lguest_dma" to point to a * network packet, similar to req_to_dma() in lguest_blk.c. The structure of a * "struct sk_buff" has grown complex over the years: it consists of a "head" * linear section pointed to by "skb->data", and possibly an array of * "fragments" in the case of a non-linear packet. * * Our receive buffers don't use fragments at all but outgoing skbs might, so * we handle it. */ static void skb_to_dma(const struct sk_buff *skb, unsigned int headlen, struct lguest_dma *dma) { unsigned int i, seg; /* First, we put the linear region into the "struct lguest_dma". Each * entry can't go over a page boundary, so even though all our packets * are 1514 bytes or less, we might need to use two entries here: */ for (i = seg = 0; i < headlen; seg++, i += rest_of_page(skb->data+i)) { dma->addr[seg] = virt_to_phys(skb->data + i); dma->len[seg] = min((unsigned)(headlen - i), rest_of_page(skb->data + i)); } /* Now we handle the fragments: at least they're guaranteed not to go * over a page. skb_shinfo(skb) returns a pointer to the structure * which tells us about the number of fragments and the fragment * array. */ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, seg++) { const skb_frag_t *f = &skb_shinfo(skb)->frags[i]; /* Should not happen with MTU less than 64k - 2 * PAGE_SIZE. */ if (seg == LGUEST_MAX_DMA_SECTIONS) { /* We will end up sending a truncated packet should * this ever happen. Plus, a cool log message! */ printk("Woah dude! Megapacket!\n"); break; } dma->addr[seg] = page_to_phys(f->page) + f->page_offset; dma->len[seg] = f->size; } /* If after all that we didn't use the entire "struct lguest_dma" * array, we terminate it with a 0 length. */ if (seg < LGUEST_MAX_DMA_SECTIONS) dma->len[seg] = 0; } /* * Packet transmission. * * Our packet transmission is a little unusual. A real network card would just * send out the packet and leave the receivers to decide if they're interested. * Instead, we look through the network device memory page and see if any of * the ethernet addresses match the packet destination, and if so we send it to * that Guest. * * This is made a little more complicated in two cases. The first case is * broadcast packets: for that we send the packet to all Guests on the network, * one at a time. The second case is "promiscuous" mode, where a Guest wants * to see all the packets on the network. We need a way for the Guest to tell * us it wants to see all packets, so it sets the "multicast" bit on its * published MAC address, which is never valid in a real ethernet address. */ #define PROMISC_BIT 0x01 /* This is the callback which is summoned whenever the network device's * multicast or promiscuous state changes. If the card is in promiscuous mode, * we advertise that in our ethernet address in the device's memory. We do the * same if Linux wants any or all multicast traffic. */ static void lguestnet_set_multicast(struct net_device *dev) { struct lguestnet_info *info = netdev_priv(dev); if ((dev->flags & (IFF_PROMISC|IFF_ALLMULTI)) || dev->mc_count) info->peer[info->me].mac[0] |= PROMISC_BIT; else info->peer[info->me].mac[0] &= ~PROMISC_BIT; } /* A simple test function to see if a peer wants to see all packets.*/ static int promisc(struct lguestnet_info *info, unsigned int peer) { return info->peer[peer].mac[0] & PROMISC_BIT; } /* Another simple function to see if a peer's advertised ethernet address * matches a packet's destination ethernet address. */ static int mac_eq(const unsigned char mac[ETH_ALEN], struct lguestnet_info *info, unsigned int peer) { /* Ignore multicast bit, which peer turns on to mean promisc. */ if ((info->peer[peer].mac[0] & (~PROMISC_BIT)) != mac[0]) return 0; return memcmp(mac+1, info->peer[peer].mac+1, ETH_ALEN-1) == 0; } /* This is the function which actually sends a packet once we've decided a * peer wants it: */ static void transfer_packet(struct net_device *dev, struct sk_buff *skb, unsigned int peernum) { struct lguestnet_info *info = netdev_priv(dev); struct lguest_dma dma; /* We use our handy "struct lguest_dma" packing function to prepare * the skb for sending. */ skb_to_dma(skb, skb_headlen(skb), &dma); pr_debug("xfer length %04x (%u)\n", htons(skb->len), skb->len); /* This is the actual send call which copies the packet. */ lguest_send_dma(peer_key(info, peernum), &dma); /* Check that the entire packet was transmitted. If not, it could mean * that the other Guest registered a short receive buffer, but this * driver should never do that. More likely, the peer is dead. */ if (dma.used_len != skb->len) { dev->stats.tx_carrier_errors++; pr_debug("Bad xfer to peer %i: %i of %i (dma %p/%i)\n", peernum, dma.used_len, skb->len, (void *)dma.addr[0], dma.len[0]); } else { /* On success we update the stats. */ dev->stats.tx_bytes += skb->len; dev->stats.tx_packets++; } } /* Another helper function to tell is if a slot in the device memory is unused. * Since we always set the Local Assignment bit in the ethernet address, the * first byte can never be 0. */ static int unused_peer(const struct lguest_net peer[], unsigned int num) { return peer[num].mac[0] == 0; } /* Finally, here is the routine which handles an outgoing packet. It's called * "start_xmit" for traditional reasons. */ static int lguestnet_start_xmit(struct sk_buff *skb, struct net_device *dev) { unsigned int i; int broadcast; struct lguestnet_info *info = netdev_priv(dev); /* Extract the destination ethernet address from the packet. */ const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest; pr_debug("%s: xmit %02x:%02x:%02x:%02x:%02x:%02x\n", dev->name, dest[0],dest[1],dest[2],dest[3],dest[4],dest[5]); /* If it's a multicast packet, we broadcast to everyone. That's not * very efficient, but there are very few applications which actually * use multicast, which is a shame really. * * As etherdevice.h points out: "By definition the broadcast address is * also a multicast address." So we don't have to test for broadcast * packets separately. */ broadcast = is_multicast_ether_addr(dest); /* Look through all the published ethernet addresses to see if we * should send this packet. */ for (i = 0; i < info->mapsize/sizeof(struct lguest_net); i++) { /* We don't send to ourselves (we actually can't SEND_DMA to * ourselves anyway), and don't send to unused slots.*/ if (i == info->me || unused_peer(info->peer, i)) continue; /* If it's broadcast we send it. If they want every packet we * send it. If the destination matches their address we send * it. Otherwise we go to the next peer. */ if (!broadcast && !promisc(info, i) && !mac_eq(dest, info, i)) continue; pr_debug("lguestnet %s: sending from %i to %i\n", dev->name, info->me, i); /* Our routine which actually does the transfer. */ transfer_packet(dev, skb, i); } /* An xmit routine is expected to dispose of the packet, so we do. */ dev_kfree_skb(skb); /* As per kernel convention, 0 means success. This is why I love * networking: even if we never sent to anyone, that's still * success! */ return 0; } /*D:560 * Packet receiving. * * First, here's a helper routine which fills one of our array of receive * buffers: */ static int fill_slot(struct net_device *dev, unsigned int slot) { struct lguestnet_info *info = netdev_priv(dev); /* We can receive ETH_DATA_LEN (1500) byte packets, plus a standard * ethernet header of ETH_HLEN (14) bytes. */ info->skb[slot] = netdev_alloc_skb(dev, ETH_HLEN + ETH_DATA_LEN); if (!info->skb[slot]) { printk("%s: could not fill slot %i\n", dev->name, slot); return -ENOMEM; } /* skb_to_dma() is a helper which sets up the "struct lguest_dma" to * point to the data in the skb: we also use it for sending out a * packet. */ skb_to_dma(info->skb[slot], ETH_HLEN + ETH_DATA_LEN, &info->dma[slot]); /* This is a Write Memory Barrier: it ensures that the entry in the * receive buffer array is written *before* we set the "used_len" entry * to 0. If the Host were looking at the receive buffer array from a * different CPU, it could potentially see "used_len = 0" and not see * the updated receive buffer information. This would be a horribly * nasty bug, so make sure the compiler and CPU know this has to happen * first. */ wmb(); /* Writing 0 to "used_len" tells the Host it can use this receive * buffer now. */ info->dma[slot].used_len = 0; return 0; } /* This is the actual receive routine. When we receive an interrupt from the * Host to tell us a packet has been delivered, we arrive here: */ static irqreturn_t lguestnet_rcv(int irq, void *dev_id) { struct net_device *dev = dev_id; struct lguestnet_info *info = netdev_priv(dev); unsigned int i, done = 0; /* Look through our entire receive array for an entry which has data * in it. */ for (i = 0; i < ARRAY_SIZE(info->dma); i++) { unsigned int length; struct sk_buff *skb; length = info->dma[i].used_len; if (length == 0) continue; /* We've found one! Remember the skb (we grabbed the length * above), and immediately refill the slot we've taken it * from. */ done++; skb = info->skb[i]; fill_slot(dev, i); /* This shouldn't happen: micropackets could be sent by a * badly-behaved Guest on the network, but the Host will never * stuff more data in the buffer than the buffer length. */ if (length < ETH_HLEN || length > ETH_HLEN + ETH_DATA_LEN) { pr_debug(KERN_WARNING "%s: unbelievable skb len: %i\n", dev->name, length); dev_kfree_skb(skb); continue; } /* skb_put(), what a great function! I've ranted about this * function before (http://lkml.org/lkml/1999/9/26/24). You * call it after you've added data to the end of an skb (in * this case, it was the Host which wrote the data). */ skb_put(skb, length); /* The ethernet header contains a protocol field: we use the * standard helper to extract it, and place the result in * skb->protocol. The helper also sets up skb->pkt_type and * eats up the ethernet header from the front of the packet. */ skb->protocol = eth_type_trans(skb, dev); /* If this device doesn't need checksums for sending, we also * don't need to check the packets when they come in. */ if (dev->features & NETIF_F_NO_CSUM) skb->ip_summed = CHECKSUM_UNNECESSARY; /* As a last resort for debugging the driver or the lguest I/O * subsystem, you can uncomment the "#define DEBUG" at the top * of this file, which turns all the pr_debug() into printk() * and floods the logs. */ pr_debug("Receiving skb proto 0x%04x len %i type %i\n", ntohs(skb->protocol), skb->len, skb->pkt_type); /* Update the packet and byte counts (visible from ifconfig, * and good for debugging). */ dev->stats.rx_bytes += skb->len; dev->stats.rx_packets++; /* Hand our fresh network packet into the stack's "network * interface receive" routine. That will free the packet * itself when it's finished. */ netif_rx(skb); } /* If we found any packets, we assume the interrupt was for us. */ return done ? IRQ_HANDLED : IRQ_NONE; } /*D:550 This is where we start: when the device is brought up by dhcpd or * ifconfig. At this point we advertise our MAC address to the rest of the * network, and register receive buffers ready for incoming packets. */ static int lguestnet_open(struct net_device *dev) { int i; struct lguestnet_info *info = netdev_priv(dev); /* Copy our MAC address into the device page, so others on the network * can find us. */ memcpy(info->peer[info->me].mac, dev->dev_addr, ETH_ALEN); /* We might already be in promisc mode (dev->flags & IFF_PROMISC). Our * set_multicast callback handles this already, so we call it now. */ lguestnet_set_multicast(dev); /* Allocate packets and put them into our "struct lguest_dma" array. * If we fail to allocate all the packets we could still limp along, * but it's a sign of real stress so we should probably give up now. */ for (i = 0; i < ARRAY_SIZE(info->dma); i++) { if (fill_slot(dev, i) != 0) goto cleanup; } /* Finally we tell the Host where our array of "struct lguest_dma" * receive buffers is, binding it to the key corresponding to the * device's physical memory plus our peerid. */ if (lguest_bind_dma(peer_key(info,info->me), info->dma, NUM_SKBS, lgdev_irq(info->lgdev)) != 0) goto cleanup; return 0; cleanup: while (--i >= 0) dev_kfree_skb(info->skb[i]); return -ENOMEM; } /*:*/ /* The close routine is called when the device is no longer in use: we clean up * elegantly. */ static int lguestnet_close(struct net_device *dev) { unsigned int i; struct lguestnet_info *info = netdev_priv(dev); /* Clear all trace of our existence out of the device memory by setting * the slot which held our MAC address to 0 (unused). */ memset(&info->peer[info->me], 0, sizeof(info->peer[info->me])); /* Unregister our array of receive buffers */ lguest_unbind_dma(peer_key(info, info->me), info->dma); for (i = 0; i < ARRAY_SIZE(info->dma); i++) dev_kfree_skb(info->skb[i]); return 0; } /*D:510 The network device probe function is basically a standard ethernet * device setup. It reads the "struct lguest_device_desc" and sets the "struct * net_device". Oh, the line-by-line excitement! Let's skip over it. :*/ static int lguestnet_probe(struct lguest_device *lgdev) { int err, irqf = IRQF_SHARED; struct net_device *dev; struct lguestnet_info *info; struct lguest_device_desc *desc = &lguest_devices[lgdev->index]; pr_debug("lguest_net: probing for device %i\n", lgdev->index); dev = alloc_etherdev(sizeof(struct lguestnet_info)); if (!dev) return -ENOMEM; SET_MODULE_OWNER(dev); /* Ethernet defaults with some changes */ ether_setup(dev); dev->set_mac_address = NULL; dev->dev_addr[0] = 0x02; /* set local assignment bit (IEEE802) */ dev->dev_addr[1] = 0x00; memcpy(&dev->dev_addr[2], &lguest_data.guestid, 2); dev->dev_addr[4] = 0x00; dev->dev_addr[5] = 0x00; dev->open = lguestnet_open; dev->stop = lguestnet_close; dev->hard_start_xmit = lguestnet_start_xmit; /* We don't actually support multicast yet, but turning on/off * promisc also calls dev->set_multicast_list. */ dev->set_multicast_list = lguestnet_set_multicast; SET_NETDEV_DEV(dev, &lgdev->dev); /* The network code complains if you have "scatter-gather" capability * if you don't also handle checksums (it seem that would be * "illogical"). So we use a lie of omission and don't tell it that we * can handle scattered packets unless we also don't want checksums, * even though to us they're completely independent. */ if (desc->features & LGUEST_NET_F_NOCSUM) dev->features = NETIF_F_SG|NETIF_F_NO_CSUM; info = netdev_priv(dev); info->mapsize = PAGE_SIZE * desc->num_pages; info->peer_phys = ((unsigned long)desc->pfn << PAGE_SHIFT); info->lgdev = lgdev; info->peer = lguest_map(info->peer_phys, desc->num_pages); if (!info->peer) { err = -ENOMEM; goto free; } /* This stores our peerid (upper bits reserved for future). */ info->me = (desc->features & (info->mapsize-1)); err = register_netdev(dev); if (err) { pr_debug("lguestnet: registering device failed\n"); goto unmap; } if (lguest_devices[lgdev->index].features & LGUEST_DEVICE_F_RANDOMNESS) irqf |= IRQF_SAMPLE_RANDOM; if (request_irq(lgdev_irq(lgdev), lguestnet_rcv, irqf, "lguestnet", dev) != 0) { pr_debug("lguestnet: cannot get irq %i\n", lgdev_irq(lgdev)); goto unregister; } pr_debug("lguestnet: registered device %s\n", dev->name); /* Finally, we put the "struct net_device" in the generic "struct * lguest_device"s private pointer. Again, it's not necessary, but * makes sure the cool kernel kids don't tease us. */ lgdev->private = dev; return 0; unregister: unregister_netdev(dev); unmap: lguest_unmap(info->peer); free: free_netdev(dev); return err; } static struct lguest_driver lguestnet_drv = { .name = "lguestnet", .owner = THIS_MODULE, .device_type = LGUEST_DEVICE_T_NET, .probe = lguestnet_probe, }; static __init int lguestnet_init(void) { return register_lguest_driver(&lguestnet_drv); } module_init(lguestnet_init); MODULE_DESCRIPTION("Lguest network driver"); MODULE_LICENSE("GPL"); /*D:580 * This is the last of the Drivers, and with this we have covered the many and * wonderous and fine (and boring) details of the Guest. * * "make Launcher" beckons, where we answer questions like "Where do Guests * come from?", and "What do you do when someone asks for optimization?" */