diff options
Diffstat (limited to 'udp.c')
| -rw-r--r-- | udp.c | 174 |
1 files changed, 174 insertions, 0 deletions
@@ -0,0 +1,174 @@ +// 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; + int 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)); + } +} + +/** + * tcp_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; + + fprintf(stderr, "udp from tap: using socket %i\n", s); + + 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; + + fprintf(stderr, "udp from tap: using socket %i\n", s); + + sendto(s, in + sizeof(*uh), len - sizeof(*uh), MSG_DONTWAIT, + (struct sockaddr *)&sa, sizeof(sa)); + } +} + +/** + * udp_sock_init() - Create and bind listening sockets for inbound connections + * @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 && + (s = sock_l4_add(c, 4, IPPROTO_UDP, htons(port))) < 0) + return -1; + udp4_sock_port[port] = s; + + if (c->v6 && + (s = sock_l4_add(c, 6, IPPROTO_UDP, htons(port))) < 0) + return -1; + udp6_sock_port[port] = s; + } + + return 0; +} |