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905ecd2b0b
c->mac isn't a great name, because it doesn't say whose mac address it is and it's not necessarily obvious in all the contexts we use it. Since this is specifically the address that we (passt/pasta) use on the tap interface, rename it to "our_tap_mac". Rename the "mac_guest" field to "guest_mac" to be grammatically consistent. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
89 lines
2.2 KiB
C
89 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* PASST - Plug A Simple Socket Transport
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* for qemu/UNIX domain socket mode
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*
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* PASTA - Pack A Subtle Tap Abstraction
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* for network namespace/tap device mode
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*
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* arp.c - ARP implementation
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*
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* Copyright (c) 2020-2021 Red Hat GmbH
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* Author: Stefano Brivio <sbrivio@redhat.com>
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*/
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#include <arpa/inet.h>
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#include <limits.h>
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#include <net/if.h>
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#include <net/if_arp.h>
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#include <netinet/if_ether.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include "util.h"
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#include "log.h"
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#include "arp.h"
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#include "dhcp.h"
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#include "passt.h"
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#include "tap.h"
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/**
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* arp() - Check if this is a supported ARP message, reply as needed
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* @c: Execution context
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* @p: Packet pool, single packet with Ethernet buffer
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*
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* Return: 1 if handled, -1 on failure
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*/
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int arp(const struct ctx *c, const struct pool *p)
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{
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unsigned char swap[4];
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struct ethhdr *eh;
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struct arphdr *ah;
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struct arpmsg *am;
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size_t l2len;
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eh = packet_get(p, 0, 0, sizeof(*eh), NULL);
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ah = packet_get(p, 0, sizeof(*eh), sizeof(*ah), NULL);
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am = packet_get(p, 0, sizeof(*eh) + sizeof(*ah), sizeof(*am), NULL);
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if (!eh || !ah || !am)
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return -1;
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if (ah->ar_hrd != htons(ARPHRD_ETHER) ||
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ah->ar_pro != htons(ETH_P_IP) ||
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ah->ar_hln != ETH_ALEN ||
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ah->ar_pln != 4 ||
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ah->ar_op != htons(ARPOP_REQUEST))
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return 1;
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/* Discard announcements (but not 0.0.0.0 "probes"): we might have the
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* same IP address, hide that.
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*/
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if (memcmp(am->sip, (unsigned char[4]){ 0 }, sizeof(am->tip)) &&
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!memcmp(am->sip, am->tip, sizeof(am->sip)))
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return 1;
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/* Don't resolve our own address, either. */
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if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip)))
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return 1;
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ah->ar_op = htons(ARPOP_REPLY);
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memcpy(am->tha, am->sha, sizeof(am->tha));
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memcpy(am->sha, c->our_tap_mac, sizeof(am->sha));
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memcpy(swap, am->tip, sizeof(am->tip));
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memcpy(am->tip, am->sip, sizeof(am->tip));
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memcpy(am->sip, swap, sizeof(am->sip));
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l2len = sizeof(*eh) + sizeof(*ah) + sizeof(*am);
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memcpy(eh->h_dest, eh->h_source, sizeof(eh->h_dest));
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memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
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tap_send_single(c, eh, l2len);
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return 1;
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}
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