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udp.c
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udp.c
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// SPDX-License-Identifier: GPL-2.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* 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, a reduced version of port-based connection tracking is implemented
* with two purposes:
* - binding ephemeral ports when they're used as source port by the guest, so
* that replies on those ports can be forwarded back to the guest, with a
* fixed timeout for this binding
* - packets received from the local host get their source changed to a local
* address (gateway address) so that they can be forwarded to the guest, and
* packets sent as replies by the guest need their destination address to
* be changed back to the address of the local host. This is dynamic to allow
* connections from the gateway as well, and uses the same fixed 180s timeout
*
* Sockets for bound ports are created at initialisation time, one set for IPv4
* and one for IPv6.
*
* Packets are forwarded back and forth, by prepending and stripping UDP headers
* in the obvious way, with no port translation.
*
* In PASTA mode, the L2-L4 translation is skipped for connections to ports
* bound between namespaces using the loopback interface, messages are directly
* transferred between L4 sockets instead. These are called spliced connections
* for consistency with the TCP implementation, but the splice() syscall isn't
* actually used as it wouldn't make sense for datagram-based connections: a
* pair of recvmmsg() and sendmmsg() deals with this case.
*
* The connection tracking for PASTA mode is slightly complicated by the absence
* of actual connections, see struct udp_splice_port, and these examples:
*
* - from init to namespace:
*
* - forward direction: 127.0.0.1:5000 -> 127.0.0.1:80 in init from socket s,
* with epoll reference: index = 80, splice = 1, orig = 1, ns = 0
* - if udp_splice_ns[V4][5000].sock:
* - send packet to udp_splice_ns[V4][5000].sock, with destination port
* 80
* - otherwise:
* - create new socket udp_splice_ns[V4][5000].sock
* - bind in namespace to 127.0.0.1:5000
* - add to epoll with reference: index = 5000, splice = 1, orig = 0,
* ns = 1
* - update udp_splice_init[V4][80].ts and udp_splice_ns[V4][5000].ts with
* current time
*
* - reverse direction: 127.0.0.1:80 -> 127.0.0.1:5000 in namespace socket s,
* having epoll reference: index = 5000, splice = 1, orig = 0, ns = 1
* - if udp_splice_init[V4][80].sock:
* - send to udp_splice_init[V4][80].sock, with destination port 5000
* - update udp_splice_init[V4][80].ts and udp_splice_ns[V4][5000].ts with
* current time
* - otherwise, discard
*
* - from namespace to init:
*
* - forward direction: 127.0.0.1:2000 -> 127.0.0.1:22 in namespace from
* socket s, with epoll reference: index = 22, splice = 1, orig = 1, ns = 1
* - if udp4_splice_init[V4][2000].sock:
* - send packet to udp_splice_init[V4][2000].sock, with destination
* port 22
* - otherwise:
* - create new socket udp_splice_init[V4][2000].sock
* - bind in init to 127.0.0.1:2000
* - add to epoll with reference: index = 2000, splice = 1, orig = 0,
* ns = 0
* - update udp_splice_ns[V4][22].ts and udp_splice_init[V4][2000].ts with
* current time
*
* - reverse direction: 127.0.0.1:22 -> 127.0.0.1:2000 in init from socket s,
* having epoll reference: index = 2000, splice = 1, orig = 0, ns = 0
* - if udp_splice_ns[V4][22].sock:
* - send to udp_splice_ns[V4][22].sock, with destination port 2000
* - update udp_splice_ns[V4][22].ts and udp_splice_init[V4][2000].ts with
* current time
* - otherwise, discard
*/
#include <sched.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <errno.h>
#include <limits.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <arpa/inet.h>
#include <time.h>
#include "checksum.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
#include "pcap.h"
#include "log.h"
#include "uthash.h"
#define UDP_CONN_TIMEOUT 180 /* s, timeout for ephemeral or local bind */
#define UDP_MAX_FRAMES 32 /* max # of frames to receive at once */
/**
* struct udp_tap_port - Port tracking based on tap-facing source port
* @sock: Socket bound to source port used as index
* @flags: Flags for local bind, loopback address/unicast address as source
* @ts: Activity timestamp from tap, used for socket aging
*/
struct udp_tap_port {
int sock;
uint8_t flags;
#define PORT_LOCAL BIT(0)
#define PORT_LOOPBACK BIT(1)
#define PORT_GUA BIT(2)
time_t ts;
};
/**
* struct udp_splice_port - Bound socket for spliced communication
* @sock: Socket bound to index port
* @ts: Activity timestamp
*/
struct udp_splice_port {
int sock;
time_t ts;
};
/* Port tracking, arrays indexed by packet source port (host order) */
static struct udp_tap_port udp_tap_map [IP_VERSIONS][NUM_PORTS];
/* "Spliced" sockets indexed by bound port (host order) */
static struct udp_splice_port udp_splice_ns [IP_VERSIONS][NUM_PORTS];
static struct udp_splice_port udp_splice_init[IP_VERSIONS][NUM_PORTS];
enum udp_act_type {
UDP_ACT_TAP,
UDP_ACT_SPLICE_NS,
UDP_ACT_SPLICE_INIT,
UDP_ACT_TYPE_MAX,
};
/* Activity-based aging for bindings */
static uint8_t udp_act[IP_VERSIONS][UDP_ACT_TYPE_MAX][DIV_ROUND_UP(NUM_PORTS, 8)];
/* Static buffers */
/**
* udp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
* @s_in: Source socket address, filled in by recvmmsg()
* @psum: Partial IP header checksum (excluding tot_len and saddr)
* @taph: Tap-level headers (partially pre-filled)
* @iph: Pre-filled IP header (except for tot_len and saddr)
* @uh: Headroom for UDP header
* @data: Storage for UDP payload
*/
static struct udp4_l2_buf_t {
struct sockaddr_in s_in;
uint32_t psum;
struct tap_hdr taph;
struct iphdr iph;
struct udphdr uh;
uint8_t data[USHRT_MAX -
(sizeof(struct iphdr) + sizeof(struct udphdr))];
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
udp4_l2_buf[UDP_MAX_FRAMES];
/**
* udp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
* @s_in6: Source socket address, filled in by recvmmsg()
* @taph: Tap-level headers (partially pre-filled)
* @ip6h: Pre-filled IP header (except for payload_len and addresses)
* @uh: Headroom for UDP header
* @data: Storage for UDP payload
*/
struct udp6_l2_buf_t {
struct sockaddr_in6 s_in6;
#ifdef __AVX2__
/* Align ip6h to 32-byte boundary. */
uint8_t pad[64 - (sizeof(struct sockaddr_in6) + sizeof(struct ethhdr) +
sizeof(uint32_t))];
#endif
struct tap_hdr taph;
struct ipv6hdr ip6h;
struct udphdr uh;
uint8_t data[USHRT_MAX -
(sizeof(struct ipv6hdr) + sizeof(struct udphdr))];
#ifdef __AVX2__
} __attribute__ ((packed, aligned(32)))
#else
} __attribute__ ((packed, aligned(__alignof__(unsigned int))))
#endif
udp6_l2_buf[UDP_MAX_FRAMES];
/* recvmmsg()/sendmmsg() data for tap */
static struct iovec udp4_l2_iov_sock [UDP_MAX_FRAMES];
static struct iovec udp6_l2_iov_sock [UDP_MAX_FRAMES];
static struct iovec udp4_l2_iov_tap [UDP_MAX_FRAMES];
static struct iovec udp6_l2_iov_tap [UDP_MAX_FRAMES];
static struct mmsghdr udp4_l2_mh_sock [UDP_MAX_FRAMES];
static struct mmsghdr udp6_l2_mh_sock [UDP_MAX_FRAMES];
/* recvmmsg()/sendmmsg() data for "spliced" connections */
static struct iovec udp4_iov_splice [UDP_MAX_FRAMES];
static struct iovec udp6_iov_splice [UDP_MAX_FRAMES];
static struct sockaddr_in udp4_localname = {
.sin_family = AF_INET,
.sin_addr = IN4ADDR_LOOPBACK_INIT,
};
static struct sockaddr_in6 udp6_localname = {
.sin6_family = AF_INET6,
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
};
static struct mmsghdr udp4_mh_splice [UDP_MAX_FRAMES];
static struct mmsghdr udp6_mh_splice [UDP_MAX_FRAMES];
struct udp_sockaddr_storage {
int s;
void *sockaddr;
socklen_t addrlen;
UT_hash_handle hh; /* makes this structure hashable */
};
static struct udp_sockaddr_storage *UDP_SOCKADDR_STORAGE = NULL;
static void add_udp_sockaddr_storage(struct udp_sockaddr_storage *us)
{
HASH_ADD_INT(UDP_SOCKADDR_STORAGE, s, us);
}
static struct udp_sockaddr_storage *find_udp_sockaddr_storage(int s)
{
struct udp_sockaddr_storage *us;
HASH_FIND_INT(UDP_SOCKADDR_STORAGE, &s, us);
return us;
}
static void delete_udp_sockaddr_storage(struct udp_sockaddr_storage *us)
{
HASH_DEL(UDP_SOCKADDR_STORAGE, us);
}
static void delete_udp_sockaddr_storage_by_s(int s)
{
struct udp_sockaddr_storage *us;
us = find_udp_sockaddr_storage(s);
if (us) {
delete_udp_sockaddr_storage(us);
if (us->sockaddr) {
free(us->sockaddr);
us->sockaddr = NULL;
}
free(us);
us = NULL;
}
}
/**
* udp_invert_portmap() - Compute reverse port translations for return packets
* @fwd: Port forwarding configuration to compute reverse map for
*/
static void udp_invert_portmap(struct udp_port_fwd *fwd)
{
int i;
ASSERT(ARRAY_SIZE(fwd->f.delta) == ARRAY_SIZE(fwd->rdelta));
for (i = 0; i < ARRAY_SIZE(fwd->f.delta); i++) {
in_port_t delta = fwd->f.delta[i];
if (delta)
fwd->rdelta[(in_port_t)i + delta] = NUM_PORTS - delta;
}
}
/**
* udp_update_check4() - Update checksum with variable parts from stored one
* @buf: L2 packet buffer with final IPv4 header
*/
static void udp_update_check4(struct udp4_l2_buf_t *buf)
{
uint32_t sum = buf->psum;
sum += buf->iph.tot_len;
sum += (buf->iph.saddr >> 16) & 0xffff;
sum += buf->iph.saddr & 0xffff;
buf->iph.check = (uint16_t)~csum_fold(sum);
}
/**
* udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
* @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/
void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
const struct in_addr *ip_da)
{
int i;
for (i = 0; i < UDP_MAX_FRAMES; i++) {
struct udp4_l2_buf_t *b4 = &udp4_l2_buf[i];
struct udp6_l2_buf_t *b6 = &udp6_l2_buf[i];
tap_update_mac(&b4->taph, eth_d, eth_s);
tap_update_mac(&b6->taph, eth_d, eth_s);
if (ip_da) {
b4->iph.daddr = ip_da->s_addr;
if (!i) {
b4->iph.saddr = 0;
b4->iph.tot_len = 0;
b4->iph.check = 0;
b4->psum = sum_16b(&b4->iph, 20);
} else {
b4->psum = udp4_l2_buf[0].psum;
}
}
}
}
/**
* udp_sock4_iov_init() - Initialise scatter-gather L2 buffers for IPv4 sockets
* @c: Execution context
*/
static void udp_sock4_iov_init(const struct ctx *c)
{
struct mmsghdr *h;
int i;
for (i = 0; i < ARRAY_SIZE(udp4_l2_buf); i++) {
udp4_l2_buf[i] = (struct udp4_l2_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IP),
.iph = L2_BUF_IP4_INIT(IPPROTO_UDP)
};
}
for (i = 0, h = udp4_l2_mh_sock; i < UDP_MAX_FRAMES; i++, h++) {
struct msghdr *mh = &h->msg_hdr;
mh->msg_name = &udp4_l2_buf[i].s_in;
mh->msg_namelen = sizeof(udp4_l2_buf[i].s_in);
udp4_l2_iov_sock[i].iov_base = udp4_l2_buf[i].data;
udp4_l2_iov_sock[i].iov_len = sizeof(udp4_l2_buf[i].data);
mh->msg_iov = &udp4_l2_iov_sock[i];
mh->msg_iovlen = 1;
}
for (i = 0; i < UDP_MAX_FRAMES; i++) {
struct iovec *iov = &udp4_l2_iov_tap[i];
iov->iov_base = tap_iov_base(c, &udp4_l2_buf[i].taph);
}
}
/**
* udp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
* @c: Execution context
*/
static void udp_sock6_iov_init(const struct ctx *c)
{
struct mmsghdr *h;
int i;
for (i = 0; i < ARRAY_SIZE(udp6_l2_buf); i++) {
udp6_l2_buf[i] = (struct udp6_l2_buf_t) {
.taph = TAP_HDR_INIT(ETH_P_IPV6),
.ip6h = L2_BUF_IP6_INIT(IPPROTO_UDP)
};
}
for (i = 0, h = udp6_l2_mh_sock; i < UDP_MAX_FRAMES; i++, h++) {
struct msghdr *mh = &h->msg_hdr;
mh->msg_name = &udp6_l2_buf[i].s_in6;
mh->msg_namelen = sizeof(struct sockaddr_in6);
udp6_l2_iov_sock[i].iov_base = udp6_l2_buf[i].data;
udp6_l2_iov_sock[i].iov_len = sizeof(udp6_l2_buf[i].data);
mh->msg_iov = &udp6_l2_iov_sock[i];
mh->msg_iovlen = 1;
}
for (i = 0; i < UDP_MAX_FRAMES; i++) {
struct iovec *iov = &udp6_l2_iov_tap[i];
iov->iov_base = tap_iov_base(c, &udp6_l2_buf[i].taph);
}
}
/**
* udp_splice_new() - Create and prepare socket for "spliced" binding
* @c: Execution context
* @v6: Set for IPv6 sockets
* @src: Source port of original connection, host order
* @splice: UDP_BACK_TO_INIT from init, UDP_BACK_TO_NS from namespace
*
* Return: prepared socket, negative error code on failure
*
* #syscalls:pasta getsockname
*/
int udp_splice_new(const struct ctx *c, int v6, in_port_t src, bool ns)
{
struct epoll_event ev = { .events = EPOLLIN | EPOLLRDHUP | EPOLLHUP };
union epoll_ref ref = { .r.proto = IPPROTO_UDP,
.r.p.udp.udp = { .splice = true, .ns = ns,
.v6 = v6, .port = src }
};
struct udp_splice_port *sp;
int act, s;
if (ns) {
sp = &udp_splice_ns[v6 ? V6 : V4][src];
act = UDP_ACT_SPLICE_NS;
} else {
sp = &udp_splice_init[v6 ? V6 : V4][src];
act = UDP_ACT_SPLICE_INIT;
}
s = socket(v6 ? AF_INET6 : AF_INET, SOCK_DGRAM | SOCK_NONBLOCK,
IPPROTO_UDP);
if (s > SOCKET_MAX) {
close(s);
return -EIO;
}
if (s < 0)
return s;
ref.r.s = s;
if (v6) {
struct sockaddr_in6 addr6 = {
.sin6_family = AF_INET6,
.sin6_port = htons(src),
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
};
if (bind(s, (struct sockaddr *)&addr6, sizeof(addr6)))
goto fail;
} else {
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = htons(src),
.sin_addr = { .s_addr = htonl(INADDR_LOOPBACK) },
};
if (bind(s, (struct sockaddr *)&addr4, sizeof(addr4)))
goto fail;
}
sp->sock = s;
bitmap_set(udp_act[v6 ? V6 : V4][act], src);
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, s, &ev);
return s;
fail:
close(s);
return -1;
}
/**
* struct udp_splice_new_ns_arg - Arguments for udp_splice_new_ns()
* @c: Execution context
* @v6: Set for IPv6
* @src: Source port of originating datagram, host order
* @dst: Destination port of originating datagram, host order
* @s: Newly created socket or negative error code
*/
struct udp_splice_new_ns_arg {
const struct ctx *c;
int v6;
in_port_t src;
int s;
};
/**
* udp_splice_new_ns() - Enter namespace and call udp_splice_new()
* @arg: See struct udp_splice_new_ns_arg
*
* Return: 0
*/
static int udp_splice_new_ns(void *arg)
{
struct udp_splice_new_ns_arg *a;
a = (struct udp_splice_new_ns_arg *)arg;
if (ns_enter(a->c))
return 0;
a->s = udp_splice_new(a->c, a->v6, a->src, true);
return 0;
}
/**
* udp_mmh_splice_port() - Is source address of message suitable for splicing?
* @v6: Is @sa a sockaddr_in6 (otherwise sockaddr_in)?
* @mmh: mmsghdr of incoming message
*
* Return: if @sa refers to localhost (127.0.0.1 or ::1) the port from
* @sa in host order, otherwise -1.
*/
static int udp_mmh_splice_port(bool v6, const struct mmsghdr *mmh)
{
const struct sockaddr_in6 *sa6 = mmh->msg_hdr.msg_name;
const struct sockaddr_in *sa4 = mmh->msg_hdr.msg_name;
if (v6 && IN6_IS_ADDR_LOOPBACK(&sa6->sin6_addr))
return ntohs(sa6->sin6_port);
if (!v6 && IN4_IS_ADDR_LOOPBACK(&sa4->sin_addr))
return ntohs(sa4->sin_port);
return -1;
}
/**
* udp_splice_sendfrom() - Send datagrams from given port to given port
* @c: Execution context
* @start: Index of first datagram in udp[46]_l2_buf
* @n: Number of datagrams to send
* @src: Datagrams will be sent from this port (on origin side)
* @dst: Datagrams will be send to this port (on destination side)
* @v6: Send as IPv6?
* @from_ns: If true send from pasta ns to init, otherwise reverse
* @allow_new: If true create sending socket if needed, if false discard
* if no sending socket is available
* @now: Timestamp
*/
static void udp_splice_sendfrom(const struct ctx *c, unsigned start, unsigned n,
in_port_t src, in_port_t dst,
bool v6, bool from_ns, bool allow_new,
const struct timespec *now)
{
struct mmsghdr *mmh_recv, *mmh_send;
unsigned int i;
int s;
if (v6) {
mmh_recv = udp6_l2_mh_sock;
mmh_send = udp6_mh_splice;
} else {
mmh_recv = udp4_l2_mh_sock;
mmh_send = udp4_mh_splice;
}
if (from_ns) {
src += c->udp.fwd_in.rdelta[src];
s = udp_splice_init[v6][src].sock;
if (!s && allow_new)
s = udp_splice_new(c, v6, src, false);
if (s < 0)
return;
udp_splice_ns[v6][dst].ts = now->tv_sec;
udp_splice_init[v6][src].ts = now->tv_sec;
} else {
src += c->udp.fwd_out.rdelta[src];
s = udp_splice_ns[v6][src].sock;
if (!s && allow_new) {
struct udp_splice_new_ns_arg arg = {
c, v6, src, -1,
};
NS_CALL(udp_splice_new_ns, &arg);
s = arg.s;
}
if (s < 0)
return;
udp_splice_init[v6][dst].ts = now->tv_sec;
udp_splice_ns[v6][src].ts = now->tv_sec;
}
for (i = start; i < start + n; i++)
mmh_send[i].msg_hdr.msg_iov->iov_len = mmh_recv[i].msg_len;
sendmmsg(s, mmh_send + start, n, MSG_NOSIGNAL);
}
/**
* udp_update_hdr4() - Update headers for one IPv4 datagram
* @c: Execution context
* @n: Index of buffer in udp4_l2_buf pool
* @dstport: Destination port number
* @now: Current timestamp
*
* Return: size of tap frame with headers
*/
static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
const struct timespec *now, int s)
{
struct udp4_l2_buf_t *b = &udp4_l2_buf[n];
in_port_t src_port;
size_t ip_len;
ip_len = udp4_l2_mh_sock[n].msg_len + sizeof(b->iph) + sizeof(b->uh);
b->iph.tot_len = htons(ip_len);
src_port = ntohs(b->s_in.sin_port);
if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_redirect) &&
IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.dns_redirect) &&
src_port == 53) {
b->iph.saddr = c->ip4.dns_host.s_addr;
} else if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_match) &&
IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.dns_host) &&
src_port == 53) {
b->iph.saddr = c->ip4.dns_match.s_addr;
} else if (IN4_IS_ADDR_LOOPBACK(&b->s_in.sin_addr) ||
IN4_IS_ADDR_UNSPECIFIED(&b->s_in.sin_addr)||
IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.addr_seen)) {
b->iph.saddr = c->ip4.gw.s_addr;
udp_tap_map[V4][src_port].ts = now->tv_sec;
udp_tap_map[V4][src_port].flags |= PORT_LOCAL;
if (IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr.s_addr, &c->ip4.addr_seen))
udp_tap_map[V4][src_port].flags &= ~PORT_LOOPBACK;
else
udp_tap_map[V4][src_port].flags |= PORT_LOOPBACK;
bitmap_set(udp_act[V4][UDP_ACT_TAP], src_port);
} else {
if (c->proxy.prox_typ == SOCKS5_PROXY && src_port != 53) {
struct udp_sockaddr_storage *us = find_udp_sockaddr_storage(s);
if (us && us->sockaddr) {
struct sockaddr *addr = us->sockaddr;
if (addr->sa_family == AF_INET) {
struct sockaddr_in *saddr = (struct sockaddr_in *)addr;
b->iph.saddr = saddr->sin_addr.s_addr;
b->s_in.sin_addr.s_addr = saddr->sin_addr.s_addr;
}
}
} else {
b->iph.saddr = b->s_in.sin_addr.s_addr;
}
}
udp_update_check4(b);
b->uh.source = b->s_in.sin_port;
b->uh.dest = htons(dstport);
b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
return tap_iov_len(c, &b->taph, ip_len);
}
/**
* udp_update_hdr6() - Update headers for one IPv6 datagram
* @c: Execution context
* @n: Index of buffer in udp6_l2_buf pool
* @dstport: Destination port number
* @now: Current timestamp
*
* Return: size of tap frame with headers
*/
static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
const struct timespec *now)
{
struct udp6_l2_buf_t *b = &udp6_l2_buf[n];
struct in6_addr *src;
in_port_t src_port;
size_t ip_len;
src = &b->s_in6.sin6_addr;
src_port = ntohs(b->s_in6.sin6_port);
ip_len = udp6_l2_mh_sock[n].msg_len + sizeof(b->ip6h) + sizeof(b->uh);
b->ip6h.payload_len = htons(udp6_l2_mh_sock[n].msg_len + sizeof(b->uh));
if (IN6_IS_ADDR_LINKLOCAL(src)) {
b->ip6h.daddr = c->ip6.addr_ll_seen;
b->ip6h.saddr = b->s_in6.sin6_addr;
} else if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_redirect) &&
IN6_ARE_ADDR_EQUAL(src, &c->ip6.dns_redirect) &&
src_port == 53) {
b->ip6h.daddr = c->ip6.addr_seen;
b->ip6h.saddr = c->ip6.dns_host;
} else if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_match) &&
IN6_ARE_ADDR_EQUAL(src, &c->ip6.dns_host) &&
src_port == 53) {
b->ip6h.daddr = c->ip6.addr_seen;
b->ip6h.saddr = c->ip6.dns_match;
} else if (IN6_IS_ADDR_LOOPBACK(src) ||
IN6_ARE_ADDR_EQUAL(src, &c->ip6.addr_seen) ||
IN6_ARE_ADDR_EQUAL(src, &c->ip6.addr)) {
b->ip6h.daddr = c->ip6.addr_ll_seen;
if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
b->ip6h.saddr = c->ip6.gw;
else
b->ip6h.saddr = c->ip6.addr_ll;
udp_tap_map[V6][src_port].ts = now->tv_sec;
udp_tap_map[V6][src_port].flags |= PORT_LOCAL;
if (IN6_IS_ADDR_LOOPBACK(src))
udp_tap_map[V6][src_port].flags |= PORT_LOOPBACK;
else
udp_tap_map[V6][src_port].flags &= ~PORT_LOOPBACK;
if (IN6_ARE_ADDR_EQUAL(src, &c->ip6.addr))
udp_tap_map[V6][src_port].flags |= PORT_GUA;
else
udp_tap_map[V6][src_port].flags &= ~PORT_GUA;
bitmap_set(udp_act[V6][UDP_ACT_TAP], src_port);
} else {
b->ip6h.daddr = c->ip6.addr_seen;
b->ip6h.saddr = b->s_in6.sin6_addr;
}
b->uh.source = b->s_in6.sin6_port;
b->uh.dest = htons(dstport);
b->uh.len = b->ip6h.payload_len;
b->ip6h.hop_limit = IPPROTO_UDP;
b->ip6h.version = b->ip6h.nexthdr = b->uh.check = 0;
b->uh.check = csum(&b->ip6h, ip_len, 0);
b->ip6h.version = 6;
b->ip6h.nexthdr = IPPROTO_UDP;
b->ip6h.hop_limit = 255;
return tap_iov_len(c, &b->taph, ip_len);
}
/**
* udp_tap_send() - Prepare UDP datagrams and send to tap interface
* @c: Execution context
* @start: Index of first datagram in udp[46]_l2_buf pool
* @n: Number of datagrams to send
* @dstport: Destination port number
* @v6: True if using IPv6
* @now: Current timestamp
*
* Return: size of tap frame with headers
*/
static void udp_tap_send(struct ctx *c,
unsigned int start, unsigned int n,
in_port_t dstport, bool v6, const struct timespec *now,
int s)
{
struct iovec *tap_iov;
unsigned int i;
if (v6)
tap_iov = udp6_l2_iov_tap;
else
tap_iov = udp4_l2_iov_tap;
for (i = start; i < start + n; i++) {
size_t buf_len;
if (v6)
buf_len = udp_update_hdr6(c, i, dstport, now);
else
buf_len = udp_update_hdr4(c, i, dstport, now, s);
tap_iov[i].iov_len = buf_len;
}
tap_send_frames(c, tap_iov + start, n);
}
/**
* udp_sock_handler() - Handle new data from socket
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
* @now: Current timestamp
*
* #syscalls recvmmsg
*/
void udp_sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
const struct timespec *now)
{
/* For not entirely clear reasons (data locality?) pasta gets
* better throughput if we receive tap datagrams one at a
* atime. For small splice datagrams throughput is slightly
* better if we do batch, but it's slightly worse for large
* splice datagrams. Since we don't know before we receive
* whether we'll use tap or splice, always go one at a time
* for pasta mode.
*/
ssize_t n = (c->mode == MODE_PASST ? UDP_MAX_FRAMES : 1);
in_port_t dstport = ref.r.p.udp.udp.port;
bool v6 = ref.r.p.udp.udp.v6;
struct mmsghdr *mmh_recv;
int i, m;
if (!(events & EPOLLIN))
return;
if (v6) {
mmh_recv = udp6_l2_mh_sock;
udp6_localname.sin6_port = htons(dstport);
} else {
mmh_recv = udp4_l2_mh_sock;
udp4_localname.sin_port = htons(dstport);
}
struct udp_sockaddr_storage *us = NULL;
if (c->proxy.prox_typ == SOCKS5_PROXY)
us = find_udp_sockaddr_storage(ref.r.s);
n = recvmmsg(ref.r.s, mmh_recv, n, 0, NULL);
if (n <= 0)
return;
int SOCKS5_UDP_HEADER_SIZE = 10;
struct sockaddr_in from_addr;
for (i = 0; i < n; ++i) {
if (c->proxy.prox_typ != SOCKS5_PROXY || !us) break;
struct msghdr* msg = &(mmh_recv[i].msg_hdr);
struct sockaddr* addr = (struct sockaddr*) msg->msg_name;
if (addr->sa_family == AF_INET)
memcpy(&from_addr, addr, sizeof(struct sockaddr_in));
else
continue;
char ip_str[INET_ADDRSTRLEN];
inet_ntop(AF_INET, &(from_addr.sin_addr), ip_str,
INET_ADDRSTRLEN);
uint16_t port = ntohs(from_addr.sin_port);
int bytes_received = mmh_recv[i].msg_len;
if (bytes_received > SOCKS5_UDP_HEADER_SIZE
&& port == strtoul(c->proxy.port, NULL, 10)) {
memmove(mmh_recv[i].msg_hdr.msg_iov->iov_base,
(char *)(mmh_recv[i].msg_hdr.msg_iov->iov_base) + SOCKS5_UDP_HEADER_SIZE,
bytes_received - SOCKS5_UDP_HEADER_SIZE);
mmh_recv[i].msg_len = bytes_received - SOCKS5_UDP_HEADER_SIZE;
if (us && us->sockaddr) {
memcpy(mmh_recv[i].msg_hdr.msg_name, us->sockaddr, us->addrlen);
mmh_recv[i].msg_hdr.msg_namelen = us->addrlen;
}
}
}
for (i = 0; i < n; i += m) {
int splicefrom = -1;
m = n;
if (ref.r.p.udp.udp.splice) {
splicefrom = udp_mmh_splice_port(v6, mmh_recv + i);
for (m = 1; i + m < n; m++) {
int p;
p = udp_mmh_splice_port(v6, mmh_recv + i + m);
if (p != splicefrom)
break;
}
}
if (splicefrom >= 0)
udp_splice_sendfrom(c, i, m, splicefrom, dstport,
v6, ref.r.p.udp.udp.ns,
ref.r.p.udp.udp.orig, now);
else
udp_tap_send(c, i, m, dstport, v6, now, ref.r.s);
}
}
/**
* udp_tap_handler() - Handle packets from tap
* @c: Execution context
* @af: Address family, AF_INET or AF_INET6
* @addr: Destination address
* @p: Pool of UDP packets, with UDP headers
* @now: Current timestamp
*
* Return: count of consumed packets
*
* #syscalls sendmmsg
*/
int udp_tap_handler(struct ctx *c, int af, const void *addr,
const struct pool *p, const struct timespec *now)
{
struct mmsghdr mm[UIO_MAXIOV];
struct iovec m[UIO_MAXIOV];
struct sockaddr_in6 s_in6;
struct sockaddr_in s_in;
struct sockaddr_in s_in_proxy;
struct sockaddr *sa;
struct sockaddr *sa_proxy;
int i, s, count = 0;
in_port_t src, dst;
struct udphdr *uh;
socklen_t sl;
socklen_t sl_proxy;
(void)c;
uh = packet_get(p, 0, 0, sizeof(*uh), NULL);
if (!uh)
return 1;
/* The caller already checks that all the messages have the same source
* and destination, so we can just take those from the first message.
*/
src = ntohs(uh->source);
dst = ntohs(uh->dest);
if (af == AF_INET) {
s_in = (struct sockaddr_in) {
.sin_family = AF_INET,
.sin_port = uh->dest,
.sin_addr = *(struct in_addr *)addr,
};
if (c->proxy.prox_typ == SOCKS5_PROXY &&
ntohs(s_in.sin_port) != 53) {
s_in_proxy = *(struct sockaddr_in *)c->proxy.addr;
sa_proxy = (struct sockaddr *)&s_in_proxy;
sl_proxy = sizeof(s_in_proxy);
}
sa = (struct sockaddr *)&s_in;
sl = sizeof(s_in);
if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_redirect) &&
IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.dns_host) &&
ntohs(s_in.sin_port) == 53) {
s_in.sin_addr = c->ip4.dns_redirect;
} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.dns_match) &&
ntohs(s_in.sin_port) == 53) {
s_in.sin_addr = c->ip4.dns_host;
} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.gw) &&
!c->no_map_gw) {
if (!(udp_tap_map[V4][dst].flags & PORT_LOCAL) ||
(udp_tap_map[V4][dst].flags & PORT_LOOPBACK))
s_in.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
else
s_in.sin_addr = c->ip4.addr_seen;
}
if (!(s = udp_tap_map[V4][src].sock)) {
union udp_epoll_ref uref = { .udp.port = src };
in_addr_t bind_addr = { 0 };
const char *bind_if = NULL;
if (!IN6_IS_ADDR_LOOPBACK(&s_in.sin_addr) &&
*c->ip6.ifname_out)
bind_if = c->ip6.ifname_out;
if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.addr_out) &&
!IN4_IS_ADDR_LOOPBACK(&s_in.sin_addr))
bind_addr = c->ip4.addr_out.s_addr;
s = sock_l4(c, AF_INET, IPPROTO_UDP, &bind_addr,
bind_if, src, uref.u32);
if (s < 0)
return p->count;
udp_tap_map[V4][src].sock = s;
bitmap_set(udp_act[V4][UDP_ACT_TAP], src);
}
udp_tap_map[V4][src].ts = now->tv_sec;
} else {
s_in6 = (struct sockaddr_in6) {
.sin6_family = AF_INET6,