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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
*
* fwd.c - Port forwarding helpers
*
* Copyright Red Hat
* Author: Stefano Brivio <sbrivio@redhat.com>
* Author: David Gibson <david@gibson.dropbear.id.au>
*/
#include <stdint.h>
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <unistd.h>
#include <stdio.h>
#include "util.h"
#include "fwd.h"
#include "passt.h"
#include "lineread.h"
/* See enum in kernel's include/net/tcp_states.h */
#define UDP_LISTEN 0x07
#define TCP_LISTEN 0x0a
/**
* procfs_scan_listen() - Set bits for listening TCP or UDP sockets from procfs
* @fd: fd for relevant /proc/net file
* @lstate: Code for listening state to scan for
* @map: Bitmap where numbers of ports in listening state will be set
* @exclude: Bitmap of ports to exclude from setting (and clear)
*
* #syscalls:pasta lseek
* #syscalls:pasta ppc64le:_llseek ppc64:_llseek armv6l:_llseek armv7l:_llseek
*/
static void procfs_scan_listen(int fd, unsigned int lstate,
uint8_t *map, const uint8_t *exclude)
{
struct lineread lr;
unsigned long port;
unsigned int state;
char *line;
if (fd < 0)
return;
if (lseek(fd, 0, SEEK_SET)) {
warn("lseek() failed on /proc/net file: %s", strerror(errno));
return;
}
lineread_init(&lr, fd);
lineread_get(&lr, &line); /* throw away header */
while (lineread_get(&lr, &line) > 0) {
/* NOLINTNEXTLINE(cert-err34-c): != 2 if conversion fails */
if (sscanf(line, "%*u: %*x:%lx %*x:%*x %x", &port, &state) != 2)
continue;
if (state != lstate)
continue;
if (bitmap_isset(exclude, port))
bitmap_clear(map, port);
else
bitmap_set(map, port);
}
}
/**
* fwd_scan_ports_tcp() - Scan /proc to update TCP forwarding map
* @fwd: Forwarding information to update
* @rev: Forwarding information for the reverse direction
*/
void fwd_scan_ports_tcp(struct fwd_ports *fwd, const struct fwd_ports *rev)
{
memset(fwd->map, 0, PORT_BITMAP_SIZE);
procfs_scan_listen(fwd->scan4, TCP_LISTEN, fwd->map, rev->map);
procfs_scan_listen(fwd->scan6, TCP_LISTEN, fwd->map, rev->map);
}
/**
* fwd_scan_ports_udp() - Scan /proc to update UDP forwarding map
* @fwd: Forwarding information to update
* @rev: Forwarding information for the reverse direction
* @tcp_fwd: Corresponding TCP forwarding information
* @tcp_rev: TCP forwarding information for the reverse direction
*/
void fwd_scan_ports_udp(struct fwd_ports *fwd, const struct fwd_ports *rev,
const struct fwd_ports *tcp_fwd,
const struct fwd_ports *tcp_rev)
{
uint8_t exclude[PORT_BITMAP_SIZE];
bitmap_or(exclude, PORT_BITMAP_SIZE, rev->map, tcp_rev->map);
memset(fwd->map, 0, PORT_BITMAP_SIZE);
procfs_scan_listen(fwd->scan4, UDP_LISTEN, fwd->map, exclude);
procfs_scan_listen(fwd->scan6, UDP_LISTEN, fwd->map, exclude);
/* Also forward UDP ports with the same numbers as bound TCP ports.
* This is useful for a handful of protocols (e.g. iperf3) where a TCP
* control port is used to set up transfers on a corresponding UDP
* port.
*
* This means we need to skip numbers of TCP ports bound on the other
* side, too. Otherwise, we would detect corresponding UDP ports as
* bound and try to forward them from the opposite side, but it's
* already us handling them.
*/
procfs_scan_listen(tcp_fwd->scan4, TCP_LISTEN, fwd->map, exclude);
procfs_scan_listen(tcp_fwd->scan6, TCP_LISTEN, fwd->map, exclude);
}
/**
* fwd_scan_ports_init() - Initial setup for automatic port forwarding
* @c: Execution context
*/
void fwd_scan_ports_init(struct ctx *c)
{
const int flags = O_RDONLY | O_CLOEXEC;
c->tcp.fwd_in.scan4 = c->tcp.fwd_in.scan6 = -1;
c->tcp.fwd_out.scan4 = c->tcp.fwd_out.scan6 = -1;
c->udp.fwd_in.f.scan4 = c->udp.fwd_in.f.scan6 = -1;
c->udp.fwd_out.f.scan4 = c->udp.fwd_out.f.scan6 = -1;
if (c->tcp.fwd_in.mode == FWD_AUTO) {
c->tcp.fwd_in.scan4 = open_in_ns(c, "/proc/net/tcp", flags);
c->tcp.fwd_in.scan6 = open_in_ns(c, "/proc/net/tcp6", flags);
fwd_scan_ports_tcp(&c->tcp.fwd_in, &c->tcp.fwd_out);
}
if (c->udp.fwd_in.f.mode == FWD_AUTO) {
c->udp.fwd_in.f.scan4 = open_in_ns(c, "/proc/net/udp", flags);
c->udp.fwd_in.f.scan6 = open_in_ns(c, "/proc/net/udp6", flags);
fwd_scan_ports_udp(&c->udp.fwd_in.f, &c->udp.fwd_out.f,
&c->tcp.fwd_in, &c->tcp.fwd_out);
}
if (c->tcp.fwd_out.mode == FWD_AUTO) {
c->tcp.fwd_out.scan4 = open("/proc/net/tcp", flags);
c->tcp.fwd_out.scan6 = open("/proc/net/tcp6", flags);
fwd_scan_ports_tcp(&c->tcp.fwd_out, &c->tcp.fwd_in);
}
if (c->udp.fwd_out.f.mode == FWD_AUTO) {
c->udp.fwd_out.f.scan4 = open("/proc/net/udp", flags);
c->udp.fwd_out.f.scan6 = open("/proc/net/udp6", flags);
fwd_scan_ports_udp(&c->udp.fwd_out.f, &c->udp.fwd_in.f,
&c->tcp.fwd_out, &c->tcp.fwd_in);
}
}
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