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// SPDX-License-Identifier: AGPL-3.0-or-later
/* PASST - Plug A Simple Socket Transport
*
* udp.c - UDP L2-L4 translation routines
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*
*/
/**
* DOC: Theory of Operation
*
*
* For UDP, no state machine or any particular tracking is required. Try to
* create and bind sets of 2^16 sockets, one for IPv4 and one for IPv6. Binding
* will fail on ports that are already bound, or low ports depending on
* capabilities.
*
* Packets are forwarded back and forth, by prepending and stripping UDP headers
* in the obvious way, with no port translation.
*
*/
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/udp.h>
#include <time.h>
#include "passt.h"
#include "tap.h"
#include "util.h"
static int udp4_sock_port[USHRT_MAX];
static int udp6_sock_port[USHRT_MAX];
/**
* udp_sock_handler() - Handle new data from socket
* @c: Execution context
* @s: File descriptor number for socket
* @events: epoll events bitmap
*/
void udp_sock_handler(struct ctx *c, int s, uint32_t events)
{
struct in6_addr a6 = { .s6_addr = { 0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0xff, 0xff,
0, 0, 0, 0 } };
struct sockaddr_storage sr, sl;
socklen_t slen = sizeof(sr);
char buf[USHRT_MAX];
struct udphdr *uh;
ssize_t n;
(void)events;
n = recvfrom(s, buf + sizeof(*uh), sizeof(buf) - sizeof(*uh),
MSG_DONTWAIT, (struct sockaddr *)&sr, &slen);
if (n < 0)
return;
uh = (struct udphdr *)buf;
if (getsockname(s, (struct sockaddr *)&sl, &slen))
return;
if (sl.ss_family == AF_INET) {
struct sockaddr_in *sr4 = (struct sockaddr_in *)&sr;
struct sockaddr_in *sl4 = (struct sockaddr_in *)&sl;
memcpy(&a6.s6_addr[12], &sr4->sin_addr, sizeof(sr4->sin_addr));
uh->source = sr4->sin_port;
uh->dest = sl4->sin_port;
uh->len = htons(n + sizeof(*uh));
tap_ip_send(c, &a6, IPPROTO_UDP, buf, n + sizeof(*uh));
} else if (sl.ss_family == AF_INET6) {
struct sockaddr_in6 *sr6 = (struct sockaddr_in6 *)&sr;
struct sockaddr_in6 *sl6 = (struct sockaddr_in6 *)&sl;
uh->source = sr6->sin6_port;
uh->dest = sl6->sin6_port;
uh->len = htons(n + sizeof(*uh));
tap_ip_send(c, &sr6->sin6_addr, IPPROTO_UDP,
buf, n + sizeof(*uh));
}
}
/**
* udp_tap_handler() - Handle packets from tap
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @in: Input buffer
* @len: Length, including UDP header
*/
void udp_tap_handler(struct ctx *c, int af, void *addr, char *in, size_t len)
{
struct udphdr *uh = (struct udphdr *)in;
int s;
(void)c;
if (af == AF_INET) {
struct sockaddr_in sa = {
.sin_family = AF_INET,
.sin_port = uh->dest,
};
if (!(s = udp4_sock_port[ntohs(uh->source)]))
return;
sa.sin_addr = *(struct in_addr *)addr;
sendto(s, in + sizeof(*uh), len - sizeof(*uh), MSG_DONTWAIT,
(struct sockaddr *)&sa, sizeof(sa));
} else if (af == AF_INET6) {
struct sockaddr_in6 sa = {
.sin6_family = AF_INET6,
.sin6_port = uh->dest,
.sin6_addr = *(struct in6_addr *)addr,
};
if (!(s = udp6_sock_port[ntohs(uh->source)]))
return;
sendto(s, in + sizeof(*uh), len - sizeof(*uh),
MSG_DONTWAIT | MSG_NOSIGNAL,
(struct sockaddr *)&sa, sizeof(sa));
}
}
/**
* udp_sock_init() - Create and bind listening sockets for inbound packets
* @c: Execution context
*
* Return: 0 on success, -1 on failure
*/
int udp_sock_init(struct ctx *c)
{
in_port_t port;
int s;
for (port = 0; port < USHRT_MAX; port++) {
if (c->v4) {
if ((s = sock_l4_add(c, 4, IPPROTO_UDP, port)) < 0)
return -1;
udp4_sock_port[port] = s;
}
if (c->v6) {
if ((s = sock_l4_add(c, 6, IPPROTO_UDP, port)) < 0)
return -1;
udp6_sock_port[port] = s;
}
}
return 0;
}
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