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passt/util.h
David Gibson 90e83d50a9 Don't take "our" MAC address from the host 
When sending frames to the guest over the tap link, we need a source MAC
address.  Currently we take that from the MAC address of the main interface
on the host, but that doesn't actually make much sense:
 * We can't preserve the real MAC address of packets from anywhere
   external so there's no transparency case here
 * In fact, it's confusingly different from how we handle IP addresses:
   whereas we give the guest the same IP as the host, we're making the
   host's MAC the one MAC that the guest *can't* use for itself.
 * We already need a fallback case if the host doesn't have an Ethernet
   like MAC (e.g. if it's connected via a point to point interface, such
   as a wireguard VPN).

Change to just just use an arbitrary fixed MAC address - I've picked
9a:55:9a:55:9a:55.  It's simpler and has the small advantage of making
the fact that passt/pasta is in use typically obvious from guest side
packet dumps.  This can still, of course, be overridden with the -M option.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
2024-08-21 12:00:28 +02:00

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/* SPDX-License-Identifier: GPL-2.0-or-later
* Copyright (c) 2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
#ifndef UTIL_H
#define UTIL_H
#include <stdlib.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <signal.h>
#include <arpa/inet.h>
#include "log.h"
#define VERSION_BLOB \
VERSION "\n" \
"Copyright Red Hat\n" \
"GNU General Public License, version 2 or later\n" \
" <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>\n" \
"This is free software: you are free to change and redistribute it.\n" \
"There is NO WARRANTY, to the extent permitted by law.\n\n"
#ifndef SECCOMP_RET_KILL_PROCESS
#define SECCOMP_RET_KILL_PROCESS SECCOMP_RET_KILL
#endif
#ifndef ETH_MAX_MTU
#define ETH_MAX_MTU USHRT_MAX
#endif
#ifndef ETH_MIN_MTU
#define ETH_MIN_MTU 68
#endif
#ifndef IP_MAX_MTU
#define IP_MAX_MTU USHRT_MAX
#endif
#ifndef MIN
#define MIN(x, y) (((x) < (y)) ? (x) : (y))
#endif
#ifndef MAX
#define MAX(x, y) (((x) > (y)) ? (x) : (y))
#endif
#define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
#define DIV_ROUND_CLOSEST(n, d) (((n) + (d) / 2) / (d))
#define ROUND_DOWN(x, y) ((x) & ~((y) - 1))
#define ROUND_UP(x, y) (((x) + (y) - 1) & ~((y) - 1))
#define MAX_FROM_BITS(n) (((1U << (n)) - 1))
#define BIT(n) (1UL << (n))
#define BITMAP_BIT(n) (BIT((n) % (sizeof(long) * 8)))
#define BITMAP_WORD(n) (n / (sizeof(long) * 8))
#define SWAP(a, b) \
do { \
__typeof__(a) __x = (a); (a) = (b); (b) = __x; \
} while (0) \
#define STRINGIFY(x) #x
#define STR(x) STRINGIFY(x)
#define ASSERT(expr) \
do { \
if (!(expr)) { \
err("ASSERTION FAILED in %s (%s:%d): %s", \
__func__, __FILE__, __LINE__, STRINGIFY(expr)); \
/* This may actually SIGSYS, due to seccomp, \
* but that will still get the job done \
*/ \
abort(); \
} \
} while (0)
#ifdef P_tmpdir
#define TMPDIR P_tmpdir
#else
#define TMPDIR "/tmp"
#endif
#define V4 0
#define V6 1
#define IP_VERSIONS 2
#define ARRAY_SIZE(a) ((int)(sizeof(a) / sizeof((a)[0])))
#define IN_INTERVAL(a, b, x) ((x) >= (a) && (x) <= (b))
#define FD_PROTO(x, proto) \
(IN_INTERVAL(c->proto.fd_min, c->proto.fd_max, (x)))
#define PORT_EPHEMERAL_MIN ((1 << 15) + (1 << 14)) /* RFC 6335 */
#define PORT_IS_EPHEMERAL(port) ((port) >= PORT_EPHEMERAL_MIN)
#define MAC_ZERO ((uint8_t [ETH_ALEN]){ 0 })
#define MAC_IS_ZERO(addr) (!memcmp((addr), MAC_ZERO, ETH_ALEN))
#ifndef __bswap_constant_16
#define __bswap_constant_16(x) \
((uint16_t) ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8)))
#endif
#ifndef __bswap_constant_32
#define __bswap_constant_32(x) \
((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >> 8) | \
(((x) & 0x0000ff00) << 8) | (((x) & 0x000000ff) << 24))
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
#define htons_constant(x) (x)
#define htonl_constant(x) (x)
#else
#define htons_constant(x) (__bswap_constant_16(x))
#define htonl_constant(x) (__bswap_constant_32(x))
#endif
/**
* ntohl_unaligned() - Read 32-bit BE value from a possibly unaligned address
* @p: Pointer to the BE value in memory
*
* Returns: Host-order value of 32-bit BE quantity at @p
*/
static inline uint32_t ntohl_unaligned(const void *p)
{
uint32_t val;
memcpy(&val, p, sizeof(val));
return ntohl(val);
}
#define NS_FN_STACK_SIZE (RLIMIT_STACK_VAL * 1024 / 8)
int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
void *arg);
#define NS_CALL(fn, arg) \
do { \
char ns_fn_stack[NS_FN_STACK_SIZE] \
__attribute__ ((aligned(__alignof__(max_align_t)))); \
\
do_clone((fn), ns_fn_stack, sizeof(ns_fn_stack), \
CLONE_VM | CLONE_VFORK | CLONE_FILES | SIGCHLD,\
(void *)(arg)); \
} while (0)
#define RCVBUF_BIG (2UL * 1024 * 1024)
#define SNDBUF_BIG (4UL * 1024 * 1024)
#define SNDBUF_SMALL (128UL * 1024)
#include <net/if.h>
#include <limits.h>
#include <stdint.h>
#include "epoll_type.h"
#include "packet.h"
struct ctx;
/* cppcheck-suppress funcArgNamesDifferent */
__attribute__ ((weak)) int ffsl(long int i) { return __builtin_ffsl(i); }
int sock_l4_sa(const struct ctx *c, enum epoll_type type,
const void *sa, socklen_t sl,
const char *ifname, bool v6only, uint32_t data);
int sock_l4(const struct ctx *c, sa_family_t af, enum epoll_type type,
const void *bind_addr, const char *ifname, uint16_t port,
uint32_t data);
void sock_probe_mem(struct ctx *c);
long timespec_diff_ms(const struct timespec *a, const struct timespec *b);
int64_t timespec_diff_us(const struct timespec *a, const struct timespec *b);
void bitmap_set(uint8_t *map, unsigned bit);
void bitmap_clear(uint8_t *map, unsigned bit);
bool bitmap_isset(const uint8_t *map, unsigned bit);
void bitmap_or(uint8_t *dst, size_t size, const uint8_t *a, const uint8_t *b);
char *line_read(char *buf, size_t len, int fd);
void ns_enter(const struct ctx *c);
bool ns_is_init(void);
int open_in_ns(const struct ctx *c, const char *path, int flags);
int pidfile_open(const char *path);
void pidfile_write(int fd, pid_t pid);
int __daemon(int pidfile_fd, int devnull_fd);
int fls(unsigned long x);
int write_file(const char *path, const char *buf);
int write_remainder(int fd, const struct iovec *iov, size_t iovcnt, size_t skip);
void close_open_files(int argc, char **argv);
/**
* af_name() - Return name of an address family
* @af: Address/protocol family (AF_INET or AF_INET6)
*
* Returns: Name of the protocol family as a string
*/
static inline const char *af_name(sa_family_t af)
{
switch (af) {
case AF_INET:
return "IPv4";
case AF_INET6:
return "IPv6";
default:
return "<unknown address family>";
}
}
#define UINT16_STRLEN (sizeof("65535"))
/* inet address (- '\0') + port (u16) (- '\0') + ':' + '\0' */
#define SOCKADDR_INET_STRLEN \
(INET_ADDRSTRLEN-1 + UINT16_STRLEN-1 + sizeof(":"))
/* inet6 address (- '\0') + port (u16) (- '\0') + '[' + ']' + ':' + '\0' */
#define SOCKADDR_INET6_STRLEN \
(INET6_ADDRSTRLEN-1 + UINT16_STRLEN-1 + sizeof("[]:"))
#define SOCKADDR_STRLEN MAX(SOCKADDR_INET_STRLEN, SOCKADDR_INET6_STRLEN)
#define ETH_ADDRSTRLEN (sizeof("00:11:22:33:44:55"))
struct sock_extended_err;
const char *sockaddr_ntop(const void *sa, char *dst, socklen_t size);
const char *eth_ntop(const unsigned char *mac, char *dst, size_t size);
const char *str_ee_origin(const struct sock_extended_err *ee);
/**
* mod_sub() - Modular arithmetic subtraction
* @a: Minued, unsigned value < @m
* @b: Subtrahend, unsigned value < @m
* @m: Modulus, must be less than (UINT_MAX / 2)
*
* Returns (@a - @b) mod @m, correctly handling unsigned underflows.
*/
static inline unsigned mod_sub(unsigned a, unsigned b, unsigned m)
{
if (a < b)
a += m;
return a - b;
}
/**
* mod_between() - Determine if a value is in a cyclic range
* @x, @i, @j: Unsigned values < @m
* @m: Modulus
*
* Returns true iff @x is in the cyclic range of values from @i..@j (mod @m),
* inclusive of @i, exclusive of @j.
*/
static inline bool mod_between(unsigned x, unsigned i, unsigned j, unsigned m)
{
return mod_sub(x, i, m) < mod_sub(j, i, m);
}
/*
* Workarounds for https://github.com/llvm/llvm-project/issues/58992
*
* For a number (maybe all) system calls that _write_ a socket address,
* clang-tidy doesn't register that the memory of the socket address will be
* initialised after the call. This can't easily be worked around with
* clang-tidy suppressions, because the warning doesn't show on the syscall
* itself but later when we access the supposedly uninitialised field.
*/
static inline void sa_init(struct sockaddr *sa, const socklen_t *sl)
{
#ifdef CLANG_TIDY_58992
if (sa)
memset(sa, 0, *sl);
#else
(void)sa;
(void)sl;
#endif /* CLANG_TIDY_58992 */
}
static inline ssize_t wrap_recvfrom(int sockfd, void *buf, size_t len,
int flags,
struct sockaddr *src_addr,
socklen_t *addrlen)
{
sa_init(src_addr, addrlen);
return recvfrom(sockfd, buf, len, flags, src_addr, addrlen);
}
#define recvfrom(s, buf, len, flags, src, addrlen) \
wrap_recvfrom((s), (buf), (len), (flags), (src), (addrlen))
static inline int wrap_accept4(int sockfd, struct sockaddr *addr,
socklen_t *addrlen, int flags)
{
sa_init(addr, addrlen);
return accept4(sockfd, addr, addrlen, flags);
}
#define accept4(s, addr, addrlen, flags) \
wrap_accept4((s), (addr), (addrlen), (flags))
#endif /* UTIL_H */
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