// SPDX-License-Identifier: GPL-2.0-or-later /* PASST - Plug A Simple Socket Transport * for qemu/UNIX domain socket mode * * PASTA - Pack A Subtle Tap Abstraction * for network namespace/tap device mode * * arp.c - ARP implementation * * Copyright (c) 2020-2021 Red Hat GmbH * Author: Stefano Brivio */ #include #include #include #include #include #include #include #include #include #include #include "util.h" #include "log.h" #include "arp.h" #include "dhcp.h" #include "passt.h" #include "tap.h" /** * arp() - Check if this is a supported ARP message, reply as needed * @c: Execution context * @p: Packet pool, single packet with Ethernet buffer * * Return: 1 if handled, -1 on failure */ int arp(const struct ctx *c, const struct pool *p) { unsigned char swap[4]; struct ethhdr *eh; struct arphdr *ah; struct arpmsg *am; size_t l2len; eh = packet_get(p, 0, 0, sizeof(*eh), NULL); ah = packet_get(p, 0, sizeof(*eh), sizeof(*ah), NULL); am = packet_get(p, 0, sizeof(*eh) + sizeof(*ah), sizeof(*am), NULL); if (!eh || !ah || !am) return -1; if (ah->ar_hrd != htons(ARPHRD_ETHER) || ah->ar_pro != htons(ETH_P_IP) || ah->ar_hln != ETH_ALEN || ah->ar_pln != 4 || ah->ar_op != htons(ARPOP_REQUEST)) return 1; /* Discard announcements, but not 0.0.0.0 "probes" */ if (memcmp(am->sip, &in4addr_any, sizeof(am->sip)) && !memcmp(am->sip, am->tip, sizeof(am->sip))) return 1; /* Don't resolve the guest's assigned address, either. */ if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip))) return 1; ah->ar_op = htons(ARPOP_REPLY); memcpy(am->tha, am->sha, sizeof(am->tha)); memcpy(am->sha, c->our_tap_mac, sizeof(am->sha)); memcpy(swap, am->tip, sizeof(am->tip)); memcpy(am->tip, am->sip, sizeof(am->tip)); memcpy(am->sip, swap, sizeof(am->sip)); l2len = sizeof(*eh) + sizeof(*ah) + sizeof(*am); memcpy(eh->h_dest, eh->h_source, sizeof(eh->h_dest)); memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source)); tap_send_single(c, eh, l2len); return 1; }