// 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
*
* passt.c - Daemon implementation
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*
* Grab Ethernet frames from AF_UNIX socket (in "passt" mode) or tap device (in
* "pasta" mode), build SOCK_DGRAM/SOCK_STREAM sockets for each 5-tuple from
* TCP, UDP packets, perform connection tracking and forward them. Forward
* packets received on sockets back to the UNIX domain socket (typically, a
* socket virtio_net file descriptor from qemu) or to the tap device (typically,
* created in a separate network namespace).
*/
#define _GNU_SOURCE
#include <sched.h>
#include <stdio.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/icmpv6.h>
#include <linux/un.h>
#include <linux/if_link.h>
#include <net/ethernet.h>
#include <stdlib.h>
#include <unistd.h>
#include <net/if.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <syslog.h>
#include <sys/stat.h>
#include "util.h"
#include "passt.h"
#include "dhcp.h"
#include "dhcpv6.h"
#include "icmp.h"
#include "tcp.h"
#include "udp.h"
#include "pcap.h"
#include "tap.h"
#include "conf.h"
#define EPOLL_EVENTS 8
#define __TIMER_INTERVAL MIN(TCP_TIMER_INTERVAL, UDP_TIMER_INTERVAL)
#define TIMER_INTERVAL MIN(__TIMER_INTERVAL, ICMP_TIMER_INTERVAL)
char pkt_buf[PKT_BUF_BYTES] __attribute__ ((aligned(PAGE_SIZE)));
char *ip_proto_str[IPPROTO_SCTP + 1] = {
[IPPROTO_ICMP] = "ICMP",
[IPPROTO_TCP] = "TCP",
[IPPROTO_UDP] = "UDP",
[IPPROTO_ICMPV6] = "ICMPV6",
[IPPROTO_SCTP] = "SCTP",
};
/**
* sock_handler() - Event handler for L4 sockets
* @c: Execution context
* @ref: epoll reference
* @events: epoll events
* @now: Current timestamp
*/
static void sock_handler(struct ctx *c, union epoll_ref ref, uint32_t events,
struct timespec *now)
{
debug("%s: %s packet from socket %i (events: 0x%08x)",
c->mode == MODE_PASST ? "passt" : "pasta",
IP_PROTO_STR(ref.proto), ref.s, events);
if (!c->no_tcp && ref.proto == IPPROTO_TCP)
tcp_sock_handler( c, ref, events, now);
else if (!c->no_udp && ref.proto == IPPROTO_UDP)
udp_sock_handler( c, ref, events, now);
else if (!c->no_icmp &&
(ref.proto == IPPROTO_ICMP || ref.proto == IPPROTO_ICMPV6))
icmp_sock_handler(c, ref, events, now);
}
/**
* post_handler() - Run periodic and deferred tasks for L4 protocol handlers
* @c: Execution context
* @now: Current timestamp
*/
static void post_handler(struct ctx *c, struct timespec *now)
{
#define CALL_PROTO_HANDLER(c, now, lc, uc) \
do { \
extern void \
lc ## _defer_handler (struct ctx *c) \
__attribute__ ((weak)); \
\
if (!c->no_ ## lc) { \
if (lc ## _defer_handler) \
lc ## _defer_handler(c); \
\
if (timespec_diff_ms((now), &c->lc.timer_run) \
>= uc ## _TIMER_INTERVAL) { \
lc ## _timer(c, now); \
c->lc.timer_run = *now; \
} \
} \
} while (0)
CALL_PROTO_HANDLER(c, now, tcp, TCP);
CALL_PROTO_HANDLER(c, now, udp, UDP);
CALL_PROTO_HANDLER(c, now, icmp, ICMP);
#undef CALL_PROTO_HANDLER
}
/**
* timer_init() - Set initial timestamp for timer runs to current time
* @c: Execution context
* @now: Current timestamp
*/
static void timer_init(struct ctx *c, struct timespec *now)
{
c->tcp.timer_run = c->udp.timer_run = c->icmp.timer_run = *now;
}
/**
* proto_update_l2_buf() - Update scatter-gather L2 buffers in protocol handlers
* @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 proto_update_l2_buf(unsigned char *eth_d, unsigned char *eth_s,
uint32_t *ip_da)
{
tcp_update_l2_buf(eth_d, eth_s, ip_da);
udp_update_l2_buf(eth_d, eth_s, ip_da);
}
static int pasta_child_pid;
static char pasta_child_ns[PATH_MAX];
/**
* pasta_ns_cleanup() - Look for processes in namespace, terminate them
*/
static void pasta_ns_cleanup(void)
{
char proc_path[PATH_MAX], ns_link[PATH_MAX];
int recheck = 0, found = 0, waited = 0;
struct dirent *dp;
DIR *dirp;
if (!*pasta_child_ns)
return;
loop:
if (!(dirp = opendir("/proc")))
return;
while ((dp = readdir(dirp))) {
pid_t pid;
errno = 0;
pid = strtol(dp->d_name, NULL, 0);
if (!pid || errno)
continue;
snprintf(proc_path, PATH_MAX, "/proc/%i/ns/net", pid);
if (readlink(proc_path, ns_link, PATH_MAX) < 0)
continue;
if (!strncmp(ns_link, pasta_child_ns, PATH_MAX)) {
found = 1;
if (waited)
kill(pid, SIGKILL);
else
kill(pid, SIGQUIT);
}
}
closedir(dirp);
if (!found)
return;
if (waited) {
if (recheck) {
info("Some processes in namespace didn't quit");
} else {
found = 0;
recheck = 1;
goto loop;
}
return;
}
info("Waiting for all processes in namespace to terminate");
sleep(1);
waited = 1;
goto loop;
}
/**
* pasta_child_handler() - Exit once shell spawned by pasta_start_ns() exits
* @signal: Unused, handler deals with SIGCHLD only
*/
static void pasta_child_handler(int signal)
{
siginfo_t infop;
(void)signal;
if (pasta_child_pid &&
!waitid(P_PID, pasta_child_pid, &infop, WEXITED | WNOHANG)) {
if (infop.si_pid == pasta_child_pid) {
pasta_ns_cleanup();
exit(EXIT_SUCCESS);
}
}
waitid(P_ALL, 0, NULL, WEXITED | WNOHANG);
}
/**
* pasta_wait_for_ns() - Busy loop until we can enter the target namespace
* @arg: Execution context
*
* Return: 0
*/
static int pasta_wait_for_ns(void *arg)
{
struct ctx *c = (struct ctx *)arg;
char ns[PATH_MAX];
if (c->netns_only)
goto netns;
snprintf(ns, PATH_MAX, "/proc/%i/ns/user", pasta_child_pid);
do
while ((c->pasta_userns_fd = open(ns, O_RDONLY)) < 0);
while (setns(c->pasta_userns_fd, 0) && !close(c->pasta_userns_fd));
netns:
snprintf(ns, PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
do
while ((c->pasta_netns_fd = open(ns, O_RDONLY)) < 0);
while (setns(c->pasta_netns_fd, 0) && !close(c->pasta_netns_fd));
return 0;
}
/**
* pasta_start_ns() - Fork shell in new namespace if target ns is not given
* @c: Execution context
*/
static void pasta_start_ns(struct ctx *c)
{
char buf[BUFSIZ], *shell;
int euid = geteuid();
int fd;
c->foreground = 1;
if (!c->debug)
c->quiet = 1;
if ((pasta_child_pid = fork()) == -1) {
perror("fork");
exit(EXIT_FAILURE);
}
if (pasta_child_pid) {
NS_CALL(pasta_wait_for_ns, c);
return;
}
if (unshare(CLONE_NEWNET | (c->netns_only ? 0 : CLONE_NEWUSER))) {
perror("unshare");
exit(EXIT_FAILURE);
}
if (!c->netns_only) {
snprintf(buf, BUFSIZ, "%u %u %u", 0, euid, 1);
fd = open("/proc/self/uid_map", O_WRONLY);
write(fd, buf, strlen(buf));
close(fd);
fd = open("/proc/self/setgroups", O_WRONLY);
write(fd, "deny", sizeof("deny"));
close(fd);
fd = open("/proc/self/gid_map", O_WRONLY);
write(fd, buf, strlen(buf));
close(fd);
}
fd = open("/proc/sys/net/ipv4/ping_group_range", O_WRONLY);
write(fd, "0 0", strlen("0 0"));
close(fd);
shell = getenv("SHELL") ? getenv("SHELL") : "/bin/sh";
if (strstr(shell, "/bash"))
execve(shell, ((char *[]) { shell, "-l", NULL }), environ);
else
execve(shell, ((char *[]) { shell, NULL }), environ);
perror("execve");
exit(EXIT_FAILURE);
}
/**
* main() - Entry point and main loop
* @argc: Argument count
* @argv: Options, plus optional target PID for pasta mode
*
* Return: 0 once interrupted, non-zero on failure
*/
int main(int argc, char **argv)
{
struct epoll_event events[EPOLL_EVENTS];
struct ctx c = { 0 };
struct rlimit limit;
struct timespec now;
char *log_name;
int nfds, i;
if (strstr(argv[0], "pasta") || strstr(argv[0], "passt4netns")) {
struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = pasta_child_handler;
sigaction(SIGCHLD, &sa, NULL);
signal(SIGPIPE, SIG_IGN);
c.mode = MODE_PASTA;
log_name = "pasta";
} else {
c.mode = MODE_PASST;
log_name = "passt";
}
if (madvise(pkt_buf, TAP_BUF_BYTES, MADV_HUGEPAGE))
perror("madvise");
openlog(log_name, 0, LOG_DAEMON);
setlogmask(LOG_MASK(LOG_EMERG));
conf(&c, argc, argv);
if (!c.debug && (c.stderr || isatty(fileno(stdout))))
openlog(log_name, LOG_PERROR, LOG_DAEMON);
if (c.mode == MODE_PASTA && !c.pasta_netns_fd) {
char proc_path[PATH_MAX];
pasta_start_ns(&c);
snprintf(proc_path, PATH_MAX, "/proc/%i/ns/net",
pasta_child_pid);
readlink(proc_path, pasta_child_ns, PATH_MAX);
}
c.epollfd = epoll_create1(0);
if (c.epollfd == -1) {
perror("epoll_create1");
exit(EXIT_FAILURE);
}
if (getrlimit(RLIMIT_NOFILE, &limit)) {
perror("getrlimit");
exit(EXIT_FAILURE);
}
limit.rlim_cur = limit.rlim_max;
if (setrlimit(RLIMIT_NOFILE, &limit)) {
perror("setrlimit");
exit(EXIT_FAILURE);
}
sock_probe_mem(&c);
tap_sock_init(&c);
clock_gettime(CLOCK_MONOTONIC, &now);
if ((!c.no_udp && udp_sock_init(&c, &now)) ||
(!c.no_tcp && tcp_sock_init(&c, &now)))
exit(EXIT_FAILURE);
proto_update_l2_buf(c.mac_guest, c.mac, &c.addr4);
if (c.v4 && !c.no_dhcp)
dhcp_init();
if (c.v6 && !c.no_dhcpv6)
dhcpv6_init(&c);
if (c.debug)
setlogmask(LOG_UPTO(LOG_DEBUG));
else if (c.quiet)
setlogmask(LOG_UPTO(LOG_ERR));
else
setlogmask(LOG_UPTO(LOG_INFO));
if (isatty(fileno(stdout)) && !c.foreground)
daemon(0, 0);
timer_init(&c, &now);
loop:
nfds = epoll_wait(c.epollfd, events, EPOLL_EVENTS, TIMER_INTERVAL);
if (nfds == -1 && errno != EINTR) {
perror("epoll_wait");
exit(EXIT_FAILURE);
}
clock_gettime(CLOCK_MONOTONIC, &now);
for (i = 0; i < nfds; i++) {
union epoll_ref ref = *((union epoll_ref *)&events[i].data.u64);
if (events[i].data.fd == c.fd_tap)
tap_handler(&c, events[i].events, &now);
else
sock_handler(&c, ref, events[i].events, &now);
}
post_handler(&c, &now);
goto loop;
return 0;
}