Re: [developer] Raw ethernet packets

[Marcel Telka <marcel@telka.sk>]

[-- Attachment #1: Type: text/plain, Size: 1460 bytes --]

On Fri, May 31, 2024 at 10:43:03AM +0200, Marcel Telka wrote:
> I'm trying to send a raw ethernet packet from an userland application
> but all my attempts so far were unsuccessful.  I basically tried two

Attached is the testing program ethersend.c that uses both bpf and
socket approaches to send the raw ethernet frame.  In both cases the
frame is silently dropped in mac_tx() because fe_tx_srs is NULL:

https://src.illumos.org/source/xref/illumos-gate/usr/src/uts/common/io/mac/mac_client.c?r=119d61cc&mo=100885&fi=3519#3576

There is attached the ethersend.d dtrace script that shows the issue:

# gcc -Wall -lsocket -o ethersend ethersend.c
# ./ethersend.d -c './ethersend e1000g0' 2>&1 | grep mac_tx
  1              -> mac_tx                    
  1               | mac_tx:entry                              0
  1              <- mac_tx                                    0
  1            -> mac_tx                      
  1             | mac_tx:entry                                0
  1            <- mac_tx                                      0
#

Since something similar reportedly works on dilos (I assume it is a fork
of old illumos-gate) then it looks like the issue is in new illumos.

I'll try to do some archaeology...

-- 
+-------------------------------------------+
| Marcel Telka   e-mail:   marcel@telka.sk  |
|                homepage: http://telka.sk/ |
+-------------------------------------------+

[-- Attachment #2: ethersend.c --]
[-- Type: text/plain, Size: 2727 bytes --]

#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <net/if.h>
#include <net/bpf.h>
#include <sys/socket.h>
#include <sys/sockio.h>

char packet[] =
	"\xff\xff\xff\xff\xff\xff"
	"\x00\x1c\x25\xa0\xb7\x2e"
	"\x08\x06\x00\x01"
	"\x08\x00\x06\x04\x00\x01"
	"\x00\x1c\x25\xa0\xb7\x2e"
	"\x0a\x00\x00\x0d"
	"\xff\xff\xff\xff\xff\xff"
	"\x0a\x00\x00\x3d"
	"\x00\x00\x00\x00\x00\x00"
	"\x00\x00\x00\x00\x00\x00"
	"\x00\x00\x00\x00\x00\x00"
;

int
send_bpf(const char *iface, char *data, size_t len)
{
	int fd = open("/dev/bpf", O_RDWR);
	if (fd < 0) {
		perror("open");
		return -1;
	}

	struct ifreq ifr;

	(void) memset(&ifr, 0, sizeof ifr);
	(void) memcpy(&ifr.ifr_name, iface, strlen(iface));
	if (ioctl(fd, BIOCSETIF, &ifr) < 0) {
		perror("BIOCSETIF");
		return -2;
	}

	int enable;
       
	enable = 1;
	if (ioctl(fd, BIOCIMMEDIATE, &enable) < 0) {
		perror("BIOCIMMEDIATE");
		return -3;
	}

	enable = 1;
	if (ioctl(fd, BIOCSHDRCMPLT, &enable) < 0) {
		perror("BIOCSHDRCMPLT");
		return -4;
	}

	size_t ret = write(fd, data, len);
	if (ret >= 0)
		printf("send_bpf sent %ld bytes\n", ret);
	if (ret != len) {
		fprintf(stderr, "write returned %ld, expected %ld\n", ret, len);
		return -5;
	}

	if (close(fd) < 0) {
		perror("close");
		return -6;
	}

	return 0;
}

int
send_socket(const char *iface, char *data, size_t len)
{
	int s = socket(AF_PACKET, SOCK_RAW, 0);
	if (s < 0) {
		perror("socket");
		return -1;
	}

	struct ifreq ifr;

	(void) memset(&ifr, 0, sizeof ifr);
	(void) memcpy(&ifr.ifr_name, iface, strlen(iface));
	if (ioctl(s, SIOCGIFINDEX, &ifr) < 0) {
		perror("SIOCGIFINDEX");
		return -2;
	}

	struct sockaddr_ll lls;
	(void) memset(&lls, 0, sizeof lls);
	lls.sll_family = AF_PACKET;
	lls.sll_protocol = 0;
	lls.sll_ifindex = ifr.ifr_index;

	if (bind(s, (struct sockaddr *)&lls, sizeof lls) < 0) {
		perror("bind");
		return -3;
	}

	size_t ret = send(s, data, len, 0);
	if (ret >= 0)
		printf("send_socket sent %ld bytes\n", ret);
	if (ret != len) {
		fprintf(stderr, "send returned %ld, expected %ld\n", ret, len);
		return -4;
	}

	if (close(s) < 0) {
		perror("close");
		return -5;
	}

	return 0;
}

int main(int argc, char *argv[])
{
	if (argc != 2) {
		fprintf(stderr, "Missing interface\n");
		return 1;
	}

	int ret;

	ret = send_bpf(argv[1], packet, sizeof packet - 1);
	if (ret != 0)
		fprintf(stderr, "send_bpf: %d\n", ret);

	ret = send_socket(argv[1], packet, sizeof packet - 1);
	if (ret != 0)
		fprintf(stderr, "send_socket: %d\n", ret);

	return 0;
}

[-- Attachment #3: ethersend.d --]
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#!/usr/sbin/dtrace -s

#pragma D option flowindent

fbt::send:entry
{
	self->t = 1;
}

fbt::write:entry
/execname == "ethersend" && arg0 > 2/
{
	self->t = 1;
}

fbt:::entry
/self->t/
{
}

fbt:::return
/self->t/
{
	trace(arg1);
}

mac_tx:entry
/self->t/
{
	trace(((mac_client_impl_t *)arg0)->mci_flent->fe_tx_srs);
}

fbt::send:return
{
	self->t = 0;
}

fbt::write:return
{
	self->t = 0;
}