605af213c5
As we support UDP forwarding for packets that are sent to local ports, we actually need some kind of connection tracking for UDP. While at it, this commit introduces a number of vaguely related fixes for issues observed while trying this out. In detail: - implement an explicit, albeit minimalistic, connection tracking for UDP, to allow usage of ephemeral ports by the guest and by the host at the same time, by binding them dynamically as needed, and to allow mapping address changes for packets with a loopback address as destination - set the guest MAC address whenever we receive a packet from tap instead of waiting for an ARP request, and set it to broadcast on start, otherwise DHCPv6 might not work if all DHCPv6 requests time out before the guest starts talking IPv4 - split context IPv6 address into address we assign, global or site address seen on tap, and link-local address seen on tap, and make sure we use the addresses we've seen as destination (link-local choice depends on source address). Similarly, for IPv4, split into address we assign and address we observe, and use the address we observe as destination - introduce a clock_gettime() syscall right after epoll_wait() wakes up, so that we can remove all the other ones and pass the current timestamp to tap and socket handlers -- this is additionally needed by UDP to time out bindings to ephemeral ports and mappings between loopback address and a local address - rename sock_l4_add() to sock_l4(), no semantic changes intended - include <arpa/inet.h> in passt.c before kernel headers so that we can use <netinet/in.h> macros to check IPv6 address types, and remove a duplicate <linux/ip.h> inclusion Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
86 lines
2 KiB
C
86 lines
2 KiB
C
// SPDX-License-Identifier: AGPL-3.0-or-later
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/* PASST - Plug A Simple Socket Transport
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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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*/
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#include <stdio.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <string.h>
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#include <linux/if_ether.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/udp.h>
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#include <net/if.h>
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#include <net/if_arp.h>
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#include <arpa/inet.h>
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#include "passt.h"
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#include "dhcp.h"
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#include "util.h"
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#include "tap.h"
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/**
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* struct arpmsg - 802.2 ARP IPv4 payload
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* @sha: Sender hardware address
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* @sip: Sender IP address
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* @tha: Target hardware address
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* @tip: Target IP address
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*/
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struct arpmsg {
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unsigned char sha[ETH_ALEN];
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unsigned char sip[4];
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unsigned char tha[ETH_ALEN];
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unsigned char tip[4];
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} __attribute__((__packed__));
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/**
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* arp() - Check if this is an ARP message, reply as needed
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* @c: Execution context
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* @len: Total L2 packet length
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* @eh: Packet buffer, Ethernet header
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*
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* Return: 0 if it's not an ARP message, 1 if handled, -1 on failure
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*/
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int arp(struct ctx *c, struct ethhdr *eh, size_t len)
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{
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struct arphdr *ah = (struct arphdr *)(eh + 1);
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struct arpmsg *am = (struct arpmsg *)(ah + 1);
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unsigned char swap[4];
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if (eh->h_proto != htons(ETH_P_ARP))
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return 0;
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if (len < sizeof(*eh) + sizeof(*ah) + sizeof(*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 || ah->ar_pln != 4 ||
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ah->ar_op != htons(ARPOP_REQUEST))
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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, ETH_ALEN);
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memcpy(am->sha, c->mac, ETH_ALEN);
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memcpy(swap, am->tip, 4);
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memcpy(am->tip, am->sip, 4);
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memcpy(am->sip, swap, 4);
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len = sizeof(*eh) + sizeof(*ah) + sizeof(*am);
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memcpy(eh->h_dest, eh->h_source, ETH_ALEN);
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memcpy(eh->h_source, c->mac, ETH_ALEN);
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if (tap_send(c->fd_unix, eh, len, 0) < 0)
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perror("ARP: send");
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return 1;
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}
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