175 lines
4 KiB
C
175 lines
4 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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* udp.c - UDP L2-L4 translation routines
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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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/**
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* DOC: Theory of Operation
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*
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*
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* For UDP, no state machine or any particular tracking is required. Try to
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* create and bind sets of 2^16 sockets, one for IPv4 and one for IPv6. Binding
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* will fail on ports that are already bound, or low ports depending on
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* capabilities.
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*
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* Packets are forwarded back and forth, by prepending and stripping UDP headers
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* in the obvious way, with no port translation.
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*
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*/
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#include <stdio.h>
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#include <errno.h>
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#include <limits.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 <stddef.h>
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#include <string.h>
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#include <sys/epoll.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <unistd.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 <time.h>
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#include "passt.h"
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#include "tap.h"
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#include "util.h"
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static int udp4_sock_port[USHRT_MAX];
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static int udp6_sock_port[USHRT_MAX];
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/**
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* udp_sock_handler() - Handle new data from socket
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* @c: Execution context
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* @s: File descriptor number for socket
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* @events: epoll events bitmap
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*/
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void udp_sock_handler(struct ctx *c, int s, uint32_t events)
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{
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struct in6_addr a6 = { .s6_addr = { 0, 0, 0, 0,
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0, 0, 0, 0,
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0, 0, 0xff, 0xff,
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0, 0, 0, 0 } };
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struct sockaddr_storage sr, sl;
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socklen_t slen = sizeof(sr);
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char buf[USHRT_MAX];
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struct udphdr *uh;
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ssize_t n;
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(void)events;
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n = recvfrom(s, buf + sizeof(*uh), sizeof(buf) - sizeof(*uh),
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MSG_DONTWAIT, (struct sockaddr *)&sr, &slen);
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if (n < 0)
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return;
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uh = (struct udphdr *)buf;
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if (getsockname(s, (struct sockaddr *)&sl, &slen))
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return;
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if (sl.ss_family == AF_INET) {
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struct sockaddr_in *sr4 = (struct sockaddr_in *)&sr;
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struct sockaddr_in *sl4 = (struct sockaddr_in *)&sl;
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memcpy(&a6.s6_addr[12], &sr4->sin_addr, sizeof(sr4->sin_addr));
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uh->source = sr4->sin_port;
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uh->dest = sl4->sin_port;
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uh->len = htons(n + sizeof(*uh));
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tap_ip_send(c, &a6, IPPROTO_UDP, buf, n + sizeof(*uh));
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} else if (sl.ss_family == AF_INET6) {
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struct sockaddr_in6 *sr6 = (struct sockaddr_in6 *)&sr;
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struct sockaddr_in6 *sl6 = (struct sockaddr_in6 *)&sl;
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uh->source = sr6->sin6_port;
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uh->dest = sl6->sin6_port;
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uh->len = htons(n + sizeof(*uh));
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tap_ip_send(c, &sr6->sin6_addr, IPPROTO_UDP,
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buf, n + sizeof(*uh));
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}
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}
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/**
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* udp_tap_handler() - Handle packets from tap
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* @c: Execution context
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* @af: Address family, AF_INET or AF_INET6
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* @in: Input buffer
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* @len: Length, including UDP header
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*/
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void udp_tap_handler(struct ctx *c, int af, void *addr, char *in, size_t len)
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{
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struct udphdr *uh = (struct udphdr *)in;
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int s;
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(void)c;
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if (af == AF_INET) {
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struct sockaddr_in sa = {
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.sin_family = AF_INET,
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.sin_port = uh->dest,
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};
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if (!(s = udp4_sock_port[ntohs(uh->source)]))
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return;
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sa.sin_addr = *(struct in_addr *)addr;
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sendto(s, in + sizeof(*uh), len - sizeof(*uh), MSG_DONTWAIT,
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(struct sockaddr *)&sa, sizeof(sa));
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} else if (af == AF_INET6) {
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struct sockaddr_in6 sa = {
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.sin6_family = AF_INET6,
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.sin6_port = uh->dest,
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.sin6_addr = *(struct in6_addr *)addr,
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};
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if (!(s = udp6_sock_port[ntohs(uh->source)]))
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return;
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sendto(s, in + sizeof(*uh), len - sizeof(*uh),
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MSG_DONTWAIT | MSG_NOSIGNAL,
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(struct sockaddr *)&sa, sizeof(sa));
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}
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}
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/**
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* udp_sock_init() - Create and bind listening sockets for inbound packets
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* @c: Execution context
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*
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* Return: 0 on success, -1 on failure
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*/
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int udp_sock_init(struct ctx *c)
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{
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in_port_t port;
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int s;
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for (port = 0; port < USHRT_MAX; port++) {
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if (c->v4) {
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if ((s = sock_l4_add(c, 4, IPPROTO_UDP, port)) < 0)
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return -1;
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udp4_sock_port[port] = s;
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}
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if (c->v6) {
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if ((s = sock_l4_add(c, 6, IPPROTO_UDP, port)) < 0)
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return -1;
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udp6_sock_port[port] = s;
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}
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}
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return 0;
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}
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