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udp.c
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udp.c
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// SPDX-License-Identifier: AGPL-3.0-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 <[email protected]>
*/
/**
* 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 bound
* socket s, with epoll reference: index = 80, splice = UDP_TO_NS
* - if udp_splice_map[V4][5000].ns_conn_sock:
* - send packet to udp4_splice_map[5000].ns_conn_sock
* - otherwise:
* - create new socket udp_splice_map[V4][5000].ns_conn_sock
* - connect in namespace to 127.0.0.1:80 (note: this destination port
* might be remapped to another port instead)
* - get source port of new connected socket (10000) with getsockname()
* - add to epoll with reference: index = 10000, splice: UDP_BACK_TO_INIT
* - set udp_splice_map[V4][10000].init_bound_sock to s
* - set udp_splice_map[V4][10000].init_dst_port to 5000
* - update udp_splice_map[V4][5000].ns_conn_ts with current time
*
* - reverse direction: 127.0.0.1:80 -> 127.0.0.1:10000 in namespace from
* connected socket s, having epoll reference: index = 10000,
* splice = UDP_BACK_TO_INIT
* - if udp_splice_map[V4][10000].init_bound_sock:
* - send to udp_splice_map[V4][10000].init_bound_sock, with destination
* port udp_splice_map[V4][10000].init_dst_port (5000)
* - otherwise, discard
*
* - from namespace to init:
*
* - forward direction: 127.0.0.1:2000 -> 127.0.0.1:22 in namespace from bound
* socket s, with epoll reference: index = 22, splice = UDP_TO_INIT
* - if udp4_splice_map[V4][2000].init_conn_sock:
* - send packet to udp4_splice_map[2000].init_conn_sock
* - otherwise:
* - create new socket udp_splice_map[V4][2000].init_conn_sock
* - connect in init to 127.0.0.1:22 (note: this destination port
* might be remapped to another port instead)
* - get source port of new connected socket (4000) with getsockname()
* - add to epoll with reference: index = 4000, splice = UDP_BACK_TO_NS
* - set udp_splice_map[V4][4000].ns_bound_sock to s
* - set udp_splice_map[V4][4000].ns_dst_port to 2000
* - update udp_splice_map[V4][4000].init_conn_ts with current time
*
* - reverse direction: 127.0.0.1:22 -> 127.0.0.1:4000 in init from connected
* socket s, having epoll reference: index = 4000, splice = UDP_BACK_TO_NS
* - if udp_splice_map[V4][4000].ns_bound_sock:
* - send to udp_splice_map[V4][4000].ns_bound_sock, with destination port
* udp_splice_map[4000].ns_dst_port (2000)
* - otherwise, discard
*/
#include <sched.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 <unistd.h>
#include <time.h>
#include <assert.h>
#include "checksum.h"
#include "util.h"
#include "passt.h"
#include "tap.h"
#include "pcap.h"
#include "log.h"
#define UDP_CONN_TIMEOUT 180 /* s, timeout for ephemeral or local bind */
#define UDP_SPLICE_FRAMES 32
#define UDP_TAP_FRAMES_MEM 32
#define UDP_TAP_FRAMES (c->mode == MODE_PASST ? UDP_TAP_FRAMES_MEM : 1)
/**
* 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 - Source port tracking for traffic between namespaces
* @ns_conn_sock: Socket connected in namespace for init source port
* @init_conn_sock: Socket connected in init for namespace source port
* @ns_conn_ts: Timestamp of activity for socket connected in namespace
* @init_conn_ts: Timestamp of activity for socket connceted in init
* @ns_dst_port: Destination port in namespace for init source port
* @init_dst_port: Destination port in init for namespace source port
* @ns_bound_sock: Bound socket in namespace for this source port in init
* @init_bound_sock: Bound socket in init for this source port in namespace
*/
struct udp_splice_port {
int ns_conn_sock;
int init_conn_sock;
time_t ns_conn_ts;
time_t init_conn_ts;
in_port_t ns_dst_port;
in_port_t init_dst_port;
int ns_bound_sock;
int init_bound_sock;
};
/* Port tracking, arrays indexed by packet source port (host order) */
static struct udp_tap_port udp_tap_map [IP_VERSIONS][NUM_PORTS];
static struct udp_splice_port udp_splice_map [IP_VERSIONS][NUM_PORTS];
enum udp_act_type {
UDP_ACT_TAP,
UDP_ACT_NS_CONN,
UDP_ACT_INIT_CONN,
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)
* @vnet_len: 4-byte qemu vnet buffer length descriptor, only for passt mode
* @eh: Pre-filled Ethernet header
* @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;
uint32_t vnet_len;
struct ethhdr eh;
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_TAP_FRAMES_MEM];
/**
* udp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
* @s_in6: Source socket address, filled in by recvmmsg()
* @vnet_len: 4-byte qemu vnet buffer length descriptor, only for passt mode
* @eh: Pre-filled Ethernet header
* @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
uint32_t vnet_len;
struct ethhdr eh;
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_TAP_FRAMES_MEM];
static struct sockaddr_storage udp_splice_namebuf;
static uint8_t udp_splice_buf[UDP_SPLICE_FRAMES][USHRT_MAX];
/* recvmmsg()/sendmmsg() data for tap */
static struct iovec udp4_l2_iov_sock [UDP_TAP_FRAMES_MEM];
static struct iovec udp6_l2_iov_sock [UDP_TAP_FRAMES_MEM];
static struct iovec udp4_l2_iov_tap [UDP_TAP_FRAMES_MEM];
static struct iovec udp6_l2_iov_tap [UDP_TAP_FRAMES_MEM];
static struct mmsghdr udp4_l2_mh_sock [UDP_TAP_FRAMES_MEM];
static struct mmsghdr udp6_l2_mh_sock [UDP_TAP_FRAMES_MEM];
static struct mmsghdr udp4_l2_mh_tap [UDP_TAP_FRAMES_MEM];
static struct mmsghdr udp6_l2_mh_tap [UDP_TAP_FRAMES_MEM];
/* recvmmsg()/sendmmsg() data for "spliced" connections */
static struct iovec udp_iov_recv [UDP_SPLICE_FRAMES];
static struct mmsghdr udp_mmh_recv [UDP_SPLICE_FRAMES];
static struct iovec udp_iov_send [UDP_SPLICE_FRAMES];
static struct mmsghdr udp_mmh_send [UDP_SPLICE_FRAMES];
static struct iovec udp_iov_sendto [UDP_SPLICE_FRAMES];
static struct mmsghdr udp_mmh_sendto [UDP_SPLICE_FRAMES];
/**
* 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_TAP_FRAMES_MEM; i++) {
struct udp4_l2_buf_t *b4 = &udp4_l2_buf[i];
struct udp6_l2_buf_t *b6 = &udp6_l2_buf[i];
if (eth_d) {
memcpy(b4->eh.h_dest, eth_d, ETH_ALEN);
memcpy(b6->eh.h_dest, eth_d, ETH_ALEN);
}
if (eth_s) {
memcpy(b4->eh.h_source, eth_s, ETH_ALEN);
memcpy(b6->eh.h_source, eth_s, ETH_ALEN);
}
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
*/
static void udp_sock4_iov_init(void)
{
struct mmsghdr *h;
int i;
for (i = 0; i < ARRAY_SIZE(udp4_l2_buf); i++) {
udp4_l2_buf[i] = (struct udp4_l2_buf_t) {
{ 0 }, 0, 0,
L2_BUF_ETH_IP4_INIT, L2_BUF_IP4_INIT(IPPROTO_UDP),
{{{ 0 }}}, { 0 },
};
}
for (i = 0, h = udp4_l2_mh_sock; i < UDP_TAP_FRAMES_MEM; 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, h = udp4_l2_mh_tap; i < UDP_TAP_FRAMES_MEM; i++, h++) {
struct msghdr *mh = &h->msg_hdr;
udp4_l2_iov_tap[i].iov_base = &udp4_l2_buf[i].vnet_len;
mh->msg_iov = &udp4_l2_iov_tap[i];
mh->msg_iovlen = 1;
}
}
/**
* udp_sock6_iov_init() - Initialise scatter-gather L2 buffers for IPv6 sockets
*/
static void udp_sock6_iov_init(void)
{
struct mmsghdr *h;
int i;
for (i = 0; i < ARRAY_SIZE(udp6_l2_buf); i++) {
udp6_l2_buf[i] = (struct udp6_l2_buf_t) {
{ 0 },
#ifdef __AVX2__
{ 0 },
#endif
0, L2_BUF_ETH_IP6_INIT, L2_BUF_IP6_INIT(IPPROTO_UDP),
{{{ 0 }}}, { 0 },
};
}
for (i = 0, h = udp6_l2_mh_sock; i < UDP_TAP_FRAMES_MEM; 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, h = udp6_l2_mh_tap; i < UDP_TAP_FRAMES_MEM; i++, h++) {
struct msghdr *mh = &h->msg_hdr;
udp6_l2_iov_tap[i].iov_base = &udp6_l2_buf[i].vnet_len;
mh->msg_iov = &udp6_l2_iov_tap[i];
mh->msg_iovlen = 1;
}
}
/**
* udp_splice_connect() - Create and connect socket for "spliced" binding
* @c: Execution context
* @v6: Set for IPv6 connections
* @bound_sock: Originating bound socket
* @src: Source port of original connection, host order
* @dst: Destination port of original connection, host order
* @splice: UDP_BACK_TO_INIT from init, UDP_BACK_TO_NS from namespace
*
* Return: connected socket, negative error code on failure
*
* #syscalls:pasta getsockname
*/
int udp_splice_connect(const struct ctx *c, int v6, int bound_sock,
in_port_t src, in_port_t dst, int splice)
{
struct epoll_event ev = { .events = EPOLLIN | EPOLLRDHUP | EPOLLHUP };
union epoll_ref ref = { .r.proto = IPPROTO_UDP,
.r.p.udp.udp = { .splice = splice, .v6 = v6 }
};
struct sockaddr_storage sa;
struct udp_splice_port *sp;
socklen_t sl = sizeof(sa);
int s;
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(dst),
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
};
if (connect(s, (struct sockaddr *)&addr6, sizeof(addr6)))
goto fail;
} else {
struct sockaddr_in addr4 = {
.sin_family = AF_INET,
.sin_port = htons(dst),
.sin_addr = { .s_addr = htonl(INADDR_LOOPBACK) },
};
if (connect(s, (struct sockaddr *)&addr4, sizeof(addr4)))
goto fail;
}
if (getsockname(s, (struct sockaddr *)&sa, &sl))
goto fail;
if (v6) {
struct sockaddr_in6 sa6;
memcpy(&sa6, &sa, sizeof(sa6));
ref.r.p.udp.udp.port = ntohs(sa6.sin6_port);
} else {
struct sockaddr_in sa4;
memcpy(&sa4, &sa, sizeof(sa4));
ref.r.p.udp.udp.port = ntohs(sa4.sin_port);
}
sp = &udp_splice_map[v6 ? V6 : V4][ref.r.p.udp.udp.port];
if (splice == UDP_BACK_TO_INIT) {
sp->init_bound_sock = bound_sock;
sp->init_dst_port = src;
udp_splice_map[v6 ? V6 : V4][src].ns_conn_sock = s;
bitmap_set(udp_act[v6 ? V6 : V4][UDP_ACT_NS_CONN], src);
} else if (splice == UDP_BACK_TO_NS) {
sp->ns_bound_sock = bound_sock;
sp->ns_dst_port = src;
udp_splice_map[v6 ? V6 : V4][src].init_conn_sock = s;
bitmap_set(udp_act[v6 ? V6 : V4][UDP_ACT_INIT_CONN], 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_connect_ns_arg - Arguments for udp_splice_connect_ns()
* @c: Execution context
* @v6: Set for inbound IPv6 connection
* @bound_sock: Originating bound socket
* @src: Source port of original connection, host order
* @dst: Destination port of original connection, host order
* @s: Newly created socket or negative error code
*/
struct udp_splice_connect_ns_arg {
const struct ctx *c;
int v6;
int bound_sock;
in_port_t src;
in_port_t dst;
int s;
};
/**
* udp_splice_connect_ns() - Enter namespace and call udp_splice_connect()
* @arg: See struct udp_splice_connect_ns_arg
*
* Return: 0
*/
static int udp_splice_connect_ns(void *arg)
{
struct udp_splice_connect_ns_arg *a;
a = (struct udp_splice_connect_ns_arg *)arg;
if (ns_enter(a->c))
return 0;
a->s = udp_splice_connect(a->c, a->v6, a->bound_sock, a->src, a->dst,
UDP_BACK_TO_INIT);
return 0;
}
/**
* udp_sock_handler_splice() - Handler for socket mapped to "spliced" connection
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
* @now: Current timestamp
*/
static void udp_sock_handler_splice(const struct ctx *c, union epoll_ref ref,
uint32_t events, const struct timespec *now)
{
in_port_t src, dst = ref.r.p.udp.udp.port, send_dst = 0;
struct msghdr *mh = &udp_mmh_recv[0].msg_hdr;
struct sockaddr_storage *sa_s = mh->msg_name;
int s, v6 = ref.r.p.udp.udp.v6, n, i;
if (!(events & EPOLLIN))
return;
n = recvmmsg(ref.r.s, udp_mmh_recv, UDP_SPLICE_FRAMES, 0, NULL);
if (n <= 0)
return;
if (v6) {
struct sockaddr_in6 *sa = (struct sockaddr_in6 *)sa_s;
src = htons(sa->sin6_port);
} else {
struct sockaddr_in *sa = (struct sockaddr_in *)sa_s;
src = ntohs(sa->sin_port);
}
switch (ref.r.p.udp.udp.splice) {
case UDP_TO_NS:
src += c->udp.fwd_out.rdelta[src];
if (!(s = udp_splice_map[v6][src].ns_conn_sock)) {
struct udp_splice_connect_ns_arg arg = {
c, v6, ref.r.s, src, dst, -1,
};
NS_CALL(udp_splice_connect_ns, &arg);
if ((s = arg.s) < 0)
return;
}
udp_splice_map[v6][src].ns_conn_ts = now->tv_sec;
break;
case UDP_BACK_TO_INIT:
if (!(s = udp_splice_map[v6][dst].init_bound_sock))
return;
send_dst = udp_splice_map[v6][dst].init_dst_port;
break;
case UDP_TO_INIT:
src += c->udp.fwd_in.rdelta[src];
if (!(s = udp_splice_map[v6][src].init_conn_sock)) {
s = udp_splice_connect(c, v6, ref.r.s, src, dst,
UDP_BACK_TO_NS);
if (s < 0)
return;
}
udp_splice_map[v6][src].init_conn_ts = now->tv_sec;
break;
case UDP_BACK_TO_NS:
if (!(s = udp_splice_map[v6][dst].ns_bound_sock))
return;
send_dst = udp_splice_map[v6][dst].ns_dst_port;
break;
default:
return;
}
if (ref.r.p.udp.udp.splice == UDP_TO_NS ||
ref.r.p.udp.udp.splice == UDP_TO_INIT) {
for (i = 0; i < n; i++) {
struct msghdr *mh_s = &udp_mmh_send[i].msg_hdr;
mh_s->msg_iov->iov_len = udp_mmh_recv[i].msg_len;
}
sendmmsg(s, udp_mmh_send, n, MSG_NOSIGNAL);
return;
}
for (i = 0; i < n; i++) {
struct msghdr *mh_s = &udp_mmh_sendto[i].msg_hdr;
mh_s->msg_iov->iov_len = udp_mmh_recv[i].msg_len;
}
if (v6) {
*((struct sockaddr_in6 *)&udp_splice_namebuf) =
((struct sockaddr_in6) {
.sin6_family = AF_INET6,
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
.sin6_port = htons(send_dst),
.sin6_scope_id = 0,
});
} else {
*((struct sockaddr_in *)&udp_splice_namebuf) =
((struct sockaddr_in) {
.sin_family = AF_INET,
.sin_addr = { .s_addr = htonl(INADDR_LOOPBACK) },
.sin_port = htons(send_dst),
.sin_zero = { 0 },
});
}
sendmmsg(s, udp_mmh_sendto, n, MSG_NOSIGNAL);
}
/**
* udp_sock_fill_data_v4() - Fill and queue one buffer. In pasta mode, write it
* @c: Execution context
* @n: Index of buffer in udp4_l2_buf pool
* @ref: epoll reference from socket
* @msg_idx: Index within message being prepared (spans multiple buffers)
* @msg_len: Length of current message being prepared for sending
* @now: Current timestamp
*/
static void udp_sock_fill_data_v4(const struct ctx *c, int n,
union epoll_ref ref,
int *msg_idx, int *msg_bufs, ssize_t *msg_len,
const struct timespec *now)
{
struct msghdr *mh = &udp6_l2_mh_tap[*msg_idx].msg_hdr;
struct udp4_l2_buf_t *b = &udp4_l2_buf[n];
size_t ip_len, buf_len;
in_port_t src_port;
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_fwd) &&
IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.dns[0]) &&
src_port == 53) {
b->iph.saddr = c->ip4.dns_fwd.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 {
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(ref.r.p.udp.udp.port);
b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
if (c->mode == MODE_PASTA) {
/* If we pass &b->eh directly to write(), starting from
* gcc 12.1, at least on aarch64 and x86_64, we get a bogus
* stringop-overread warning, due to:
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103483
*
* but we can't disable it with a pragma, because it will be
* ignored if LTO is enabled:
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80922
*/
void *frame = (char *)b + offsetof(struct udp4_l2_buf_t, eh);
if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0)
debug("tap write: %s", strerror(errno));
pcap(frame, sizeof(b->eh) + ip_len);
return;
}
b->vnet_len = htonl(ip_len + sizeof(struct ethhdr));
buf_len = sizeof(uint32_t) + sizeof(struct ethhdr) + ip_len;
udp4_l2_iov_tap[n].iov_len = buf_len;
/* With bigger messages, qemu closes the connection. */
if (*msg_bufs && *msg_len + buf_len > SHRT_MAX) {
mh->msg_iovlen = *msg_bufs;
(*msg_idx)++;
udp4_l2_mh_tap[*msg_idx].msg_hdr.msg_iov = &udp4_l2_iov_tap[n];
*msg_len = *msg_bufs = 0;
}
*msg_len += buf_len;
(*msg_bufs)++;
}
/**
* udp_sock_fill_data_v4() - Fill and queue one buffer. In pasta mode, write it
* @c: Execution context
* @n: Index of buffer in udp4_l2_buf pool
* @ref: epoll reference from socket
* @msg_idx: Index within message being prepared (spans multiple buffers)
* @msg_len: Length of current message being prepared for sending
* @now: Current timestamp
*/
static void udp_sock_fill_data_v6(const struct ctx *c, int n,
union epoll_ref ref,
int *msg_idx, int *msg_bufs, ssize_t *msg_len,
const struct timespec *now)
{
struct msghdr *mh = &udp6_l2_mh_tap[*msg_idx].msg_hdr;
struct udp6_l2_buf_t *b = &udp6_l2_buf[n];
size_t ip_len, buf_len;
struct in6_addr *src;
in_port_t src_port;
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_fwd) &&
IN6_ARE_ADDR_EQUAL(src, &c->ip6.dns[0]) && src_port == 53) {
b->ip6h.daddr = c->ip6.addr_seen;
b->ip6h.saddr = c->ip6.dns_fwd;
} 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(ref.r.p.udp.udp.port);
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;
if (c->mode == MODE_PASTA) {
/* See udp_sock_fill_data_v4() for the reason behind 'frame' */
void *frame = (char *)b + offsetof(struct udp6_l2_buf_t, eh);
if (write(c->fd_tap, frame, sizeof(b->eh) + ip_len) < 0)
debug("tap write: %s", strerror(errno));
pcap(frame, sizeof(b->eh) + ip_len);
return;
}
b->vnet_len = htonl(ip_len + sizeof(struct ethhdr));
buf_len = sizeof(uint32_t) + sizeof(struct ethhdr) + ip_len;
udp6_l2_iov_tap[n].iov_len = buf_len;
/* With bigger messages, qemu closes the connection. */
if (*msg_bufs && *msg_len + buf_len > SHRT_MAX) {
mh->msg_iovlen = *msg_bufs;
(*msg_idx)++;
udp6_l2_mh_tap[*msg_idx].msg_hdr.msg_iov = &udp6_l2_iov_tap[n];
*msg_len = *msg_bufs = 0;
}
*msg_len += buf_len;
(*msg_bufs)++;
}
/**
* udp_sock_handler() - Handle new data from socket
* @c: Execution context
* @ref: epoll reference
* @events: epoll events bitmap
* @now: Current timestamp
*
* #syscalls recvmmsg
* #syscalls:passt sendmmsg sendmsg
*/
void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events,
const struct timespec *now)
{
ssize_t n, msg_len = 0, missing = 0;
int msg_bufs = 0, msg_i = 0, ret;
struct mmsghdr *tap_mmh;
struct msghdr *last_mh;
unsigned int i;
if (events == EPOLLERR)
return;
if (ref.r.p.udp.udp.splice) {
udp_sock_handler_splice(c, ref, events, now);
return;
}
if (ref.r.p.udp.udp.v6) {
n = recvmmsg(ref.r.s, udp6_l2_mh_sock, UDP_TAP_FRAMES, 0, NULL);
if (n <= 0)
return;
udp6_l2_mh_tap[0].msg_hdr.msg_iov = &udp6_l2_iov_tap[0];
for (i = 0; i < (unsigned)n; i++) {
udp_sock_fill_data_v6(c, i, ref,
&msg_i, &msg_bufs, &msg_len, now);
}
udp6_l2_mh_tap[msg_i].msg_hdr.msg_iovlen = msg_bufs;
tap_mmh = udp6_l2_mh_tap;
} else {
n = recvmmsg(ref.r.s, udp4_l2_mh_sock, UDP_TAP_FRAMES, 0, NULL);
if (n <= 0)
return;
udp6_l2_mh_tap[0].msg_hdr.msg_iov = &udp6_l2_iov_tap[0];
for (i = 0; i < (unsigned)n; i++) {
udp_sock_fill_data_v4(c, i, ref,
&msg_i, &msg_bufs, &msg_len, now);
}
udp4_l2_mh_tap[msg_i].msg_hdr.msg_iovlen = msg_bufs;
tap_mmh = udp4_l2_mh_tap;
}
if (c->mode == MODE_PASTA)
return;
ret = sendmmsg(c->fd_tap, tap_mmh, msg_i + 1,
MSG_NOSIGNAL | MSG_DONTWAIT);
if (ret <= 0)
return;
/* If we lose some messages to sendmmsg() here, fine, it's UDP. However,
* the last message needs to be delivered completely, otherwise qemu
* will fail to reassemble the next message and close the connection. Go
* through headers from the last sent message, counting bytes, and, if
* and as soon as we see more bytes than sendmmsg() sent, re-send the
* rest with a blocking call.
*
* In pictures, given this example:
*
* iov #0 iov #1 iov #2 iov #3
* tap_mmh[ret - 1].msg_hdr: .... ...... ..... ......
* tap_mmh[ret - 1].msg_len: 7 .... ...
*
* when 'msglen' reaches: 10 ^
* and 'missing' below is: 3 ---
*
* re-send everything from here: ^-- ----- ------
*/
last_mh = &tap_mmh[ret - 1].msg_hdr;
for (i = 0, msg_len = 0; i < last_mh->msg_iovlen; i++) {
if (missing <= 0) {
msg_len += last_mh->msg_iov[i].iov_len;
missing = msg_len - tap_mmh[ret - 1].msg_len;
}
if (missing > 0) {
uint8_t **iov_base;
int first_offset;
iov_base = (uint8_t **)&last_mh->msg_iov[i].iov_base;
first_offset = last_mh->msg_iov[i].iov_len - missing;
*iov_base += first_offset;
last_mh->msg_iov[i].iov_len = missing;
last_mh->msg_iov = &last_mh->msg_iov[i];
if (sendmsg(c->fd_tap, last_mh, MSG_NOSIGNAL) < 0)
debug("UDP: %li bytes to tap missing", missing);
*iov_base -= first_offset;
break;
}
}
pcapmm(tap_mmh, ret);
}
/**
* 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 *sa;
int i, s, count = 0;
in_port_t src, dst;
struct udphdr *uh;
socklen_t sl;
(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,
};