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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
*
* pcap.c - Packet capture for PASST/PASTA
*
* Copyright (c) 2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*/
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <errno.h>
#include <net/ethernet.h>
#include <netinet/in.h>
#include <unistd.h>
#include <net/if.h>
#include "util.h"
#include "passt.h"
#include "log.h"
#include "pcap.h"
#include "iov.h"
#define PCAP_VERSION_MINOR 4
static int pcap_fd = -1;
/* See pcap.h from libpcap, or pcap-savefile(5) */
static const struct {
uint32_t magic;
#define PCAP_MAGIC 0xa1b2c3d4
uint16_t major;
#define PCAP_VERSION_MAJOR 2
uint16_t minor;
#define PCAP_VERSION_MINOR 4
int32_t thiszone;
uint32_t sigfigs;
uint32_t snaplen;
uint32_t linktype;
#define PCAP_LINKTYPE_ETHERNET 1
} pcap_hdr = {
PCAP_MAGIC, PCAP_VERSION_MAJOR, PCAP_VERSION_MINOR, 0, 0, ETH_MAX_MTU,
PCAP_LINKTYPE_ETHERNET
};
struct pcap_pkthdr {
uint32_t tv_sec;
uint32_t tv_usec;
uint32_t caplen;
uint32_t len;
};
/**
* pcap_frame() - Capture a single frame to pcap file with given timestamp
* @iov: IO vector containing frame (with L2 headers and tap headers)
* @iovcnt: Number of buffers (@iov entries) in frame
* @offset: Byte offset of the L2 headers within @iov
* @now: Timestamp
*
* Returns: 0 on success, -errno on error writing to the file
*/
static void pcap_frame(const struct iovec *iov, size_t iovcnt,
size_t offset, const struct timespec *now)
{
size_t l2len = iov_size(iov, iovcnt) - offset;
struct pcap_pkthdr h = {
.tv_sec = now->tv_sec,
.tv_usec = DIV_ROUND_CLOSEST(now->tv_nsec, 1000),
.caplen = l2len,
.len = l2len
};
struct iovec hiov = { &h, sizeof(h) };
if (write_remainder(pcap_fd, &hiov, 1, 0) < 0 ||
write_remainder(pcap_fd, iov, iovcnt, offset) < 0)
debug_perror("Cannot log packet, length %zu", l2len);
}
/**
* pcap() - Capture a single frame to pcap file
* @pkt: Pointer to data buffer, including L2 headers
* @l2len: L2 frame length
*/
void pcap(const char *pkt, size_t l2len)
{
struct iovec iov = { (char *)pkt, l2len };
struct timespec now;
if (pcap_fd == -1)
return;
clock_gettime(CLOCK_REALTIME, &now);
pcap_frame(&iov, 1, 0, &now);
}
/**
* pcap_multiple() - Capture multiple frames
* @iov: IO vector with @frame_parts * @n entries
* @frame_parts: Number of IO vector items for each frame
* @n: Number of frames to capture
* @offset: Offset of the L2 frame within each iovec buffer
*/
void pcap_multiple(const struct iovec *iov, size_t frame_parts, unsigned int n,
size_t offset)
{
struct timespec now;
unsigned int i;
if (pcap_fd == -1)
return;
clock_gettime(CLOCK_REALTIME, &now);
for (i = 0; i < n; i++)
pcap_frame(iov + i * frame_parts, frame_parts, offset, &now);
}
/*
* pcap_iov - Write packet data described by an I/O vector
* to a pcap file descriptor.
*
* @iov: Pointer to the array of struct iovec describing the I/O vector
* containing packet data to write, including L2 header
* @iovcnt: Number of buffers (@iov entries)
*/
void pcap_iov(const struct iovec *iov, size_t iovcnt)
{
struct timespec now;
if (pcap_fd == -1)
return;
clock_gettime(CLOCK_REALTIME, &now);
pcap_frame(iov, iovcnt, 0, &now);
}
/**
* pcap_init() - Initialise pcap file
* @c: Execution context
*/
void pcap_init(struct ctx *c)
{
int flags = O_WRONLY | O_CREAT | O_TRUNC;
if (pcap_fd != -1)
return;
if (!*c->pcap)
return;
flags |= c->foreground ? O_CLOEXEC : 0;
pcap_fd = open(c->pcap, flags, S_IRUSR | S_IWUSR);
if (pcap_fd == -1) {
perror("open");
return;
}
info("Saving packet capture to %s", c->pcap);
if (write(pcap_fd, &pcap_hdr, sizeof(pcap_hdr)) < 0)
warn_perror("Cannot write PCAP header");
}
|