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https://passt.top/passt
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17337a736f
With -DDEBUG, passt now saves guest-side traffic captures in pcap format at /tmp/passt_<ISO8601 timestamp>.pcap. The timestamp refers to time and date of start-up. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
143 lines
3.3 KiB
C
143 lines
3.3 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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* tap.c - Functions to communicate with guest-facing tap interface
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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 <limits.h>
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#include <string.h>
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#include <net/ethernet.h>
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#include <net/if.h>
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#include <netinet/in.h>
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#include <stdint.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/tcp.h>
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#include <linux/udp.h>
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#include <linux/icmp.h>
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#include <linux/icmpv6.h>
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#include "passt.h"
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#include "util.h"
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#include "pcap.h"
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/**
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* tap_send() - Send frame and qemu socket header with indication of length
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* @fd: tap file descriptor
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* @len: Total L2 packet length
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* @flags: Flags for send(), if any
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*
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* Return: return code from send()
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*/
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int tap_send(int fd, void *data, size_t len, int flags)
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{
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uint32_t vnet_len = htonl(len);
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send(fd, &vnet_len, 4, MSG_DONTWAIT | MSG_NOSIGNAL);
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pcap(data, len);
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return send(fd, data, len, flags | MSG_DONTWAIT | MSG_NOSIGNAL);
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}
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/**
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* tap_ip_send() - Send IP packet, with L2 headers, calculating L3/L4 checksums
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* @c: Execution context
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* @src: IPv6 source address, IPv4-mapped for IPv4 sources
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* @proto: L4 protocol number
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* @in: Payload
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* @len: L4 payload length
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*/
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void tap_ip_send(struct ctx *c, struct in6_addr *src, uint8_t proto,
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char *in, size_t len)
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{
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char pkt[USHRT_MAX];
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struct ethhdr *eh;
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eh = (struct ethhdr *)pkt;
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/* TODO: ARP table lookup */
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memcpy(eh->h_dest, c->mac_guest, ETH_ALEN);
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memcpy(eh->h_source, c->mac, ETH_ALEN);
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if (IN6_IS_ADDR_V4MAPPED(src)) {
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struct iphdr *iph = (struct iphdr *)(eh + 1);
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char *data = (char *)(iph + 1);
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eh->h_proto = ntohs(ETH_P_IP);
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iph->version = 4;
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iph->ihl = 5;
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iph->tos = 0;
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iph->tot_len = htons(len + 20);
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iph->id = 0;
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iph->frag_off = 0;
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iph->ttl = 255;
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iph->protocol = proto;
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iph->daddr = c->addr4_seen;
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memcpy(&iph->saddr, &src->s6_addr[12], 4);
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iph->check = 0;
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iph->check = csum_ip4(iph, iph->ihl * 4);
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memcpy(data, in, len);
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if (iph->protocol == IPPROTO_TCP) {
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csum_tcp4(iph);
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} else if (iph->protocol == IPPROTO_UDP) {
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struct udphdr *uh = (struct udphdr *)(iph + 1);
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uh->check = 0;
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}
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tap_send(c->fd_unix, pkt, len + sizeof(*iph) + sizeof(*eh), 0);
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} else {
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struct ipv6hdr *ip6h = (struct ipv6hdr *)(eh + 1);
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char *data = (char *)(ip6h + 1);
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eh->h_proto = ntohs(ETH_P_IPV6);
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memset(ip6h->flow_lbl, 0, 3);
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ip6h->payload_len = htons(len);
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ip6h->priority = 0;
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ip6h->saddr = *src;
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if (IN6_IS_ADDR_LINKLOCAL(src))
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ip6h->daddr = c->addr6_ll_seen;
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else
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ip6h->daddr = c->addr6_seen;
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memcpy(data, in, len);
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ip6h->hop_limit = proto;
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ip6h->version = 0;
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ip6h->nexthdr = 0;
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if (proto == IPPROTO_TCP) {
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struct tcphdr *th = (struct tcphdr *)(ip6h + 1);
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th->check = 0;
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th->check = csum_ip4(ip6h, len + sizeof(*ip6h));
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} else if (proto == IPPROTO_UDP) {
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struct udphdr *uh = (struct udphdr *)(ip6h + 1);
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uh->check = 0;
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uh->check = csum_ip4(ip6h, len + sizeof(*ip6h));
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} else if (proto == IPPROTO_ICMPV6) {
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struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
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ih->icmp6_cksum = 0;
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ih->icmp6_cksum = csum_ip4(ip6h, len + sizeof(*ip6h));
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}
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ip6h->version = 6;
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ip6h->nexthdr = proto;
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ip6h->hop_limit = 255;
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tap_send(c->fd_unix, pkt, len + sizeof(*ip6h) + sizeof(*eh), 0);
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}
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}
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