105b916361
This is a reimplementation, partially building on the earlier draft, that uses L4 sockets (SOCK_DGRAM, SOCK_STREAM) instead of SOCK_RAW, providing L4-L2 translation functionality without requiring any security capability. Conceptually, this follows the design presented at: https://gitlab.com/abologna/kubevirt-and-kvm/-/blob/master/Networking.md The most significant novelty here comes from TCP and UDP translation layers. In particular, the TCP state and translation logic follows the intent of being minimalistic, without reimplementing a full TCP stack in either direction, and synchronising as much as possible the TCP dynamic and flows between guest and host kernel. Another important introduction concerns addressing, port translation and forwarding. The Layer 4 implementations now attempt to bind on all unbound ports, in order to forward connections in a transparent way. While at it: - the qemu 'tap' back-end can't be used as-is by qrap anymore, because of explicit checks now introduced in qemu to ensure that the corresponding file descriptor is actually a tap device. For this reason, qrap now operates on a 'socket' back-end type, accounting for and building the additional header reporting frame length - provide a demo script that sets up namespaces, addresses and routes, and starts the daemon. A virtual machine started in the network namespace, wrapped by qrap, will now directly interface with passt and communicate using Layer 4 sockets provided by the host kernel. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
136 lines
3.2 KiB
C
136 lines
3.2 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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* 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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/**
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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, 0);
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return send(fd, data, len, flags);
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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;
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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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ip6h->daddr = c->addr6_guest;
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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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