xref: /src/usr.sbin/ndbootd/config/ndbootd-bpf.c

/*	$NetBSD: ndbootd-bpf.c,v 1.2 2001/05/22 14:41:59 fredette Exp $	*/

/* ndbootd-bpf.c - the Sun Network Disk (nd) daemon BPF component: */

/*
 * Copyright (c) 2001 Matthew Fredette.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *   3. All advertising materials mentioning features or use of this software
 *      must display the following acknowledgement:
 *        This product includes software developed by Matthew Fredette.
 *   4. The name of Matthew Fredette may not be used to endorse or promote
 *      products derived from this software without specific prior written
 *      permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

/* <<Header: /data/home/fredette/project/THE-WEIGHT-CVS/ndbootd/config/ndbootd-bpf.c,v 1.3 2001/05/22 13:13:24 fredette Exp >> */

/*
 * <<Log: ndbootd-bpf.c,v >>
 * Revision 1.3  2001/05/22 13:13:24  fredette
 * Ran indent(1) with NetBSD's KNF-approximating profile.
 *
 * Revision 1.2  2001/05/09 20:50:46  fredette
 * Removed an unnecessary comment.
 *
 * Revision 1.1  2001/01/29 15:12:13  fredette
 * Added.
 *
 */

static const char _ndbootd_bpf_c_rcsid[] = "<<Id: ndbootd-bpf.c,v 1.3 2001/05/22 13:13:24 fredette Exp >>";

/* includes: */
#include <net/bpf.h>

/* structures: */
struct _ndbootd_interface_bpf {

	/* the size of the packet buffer for the interface: */
	size_t _ndbootd_interface_bpf_buffer_size;

	/* the packet buffer for the interface: */
	char *_ndbootd_interface_bpf_buffer;

	/* the next offset within the packet buffer, and the end of the data
	 * in the packet buffer: */
	size_t _ndbootd_interface_bpf_buffer_offset;
	size_t _ndbootd_interface_bpf_buffer_end;
};

/* the BPF program to capture ND packets: */
static struct bpf_insn ndboot_bpf_filter[] = {

	/* drop this packet if its ethertype isn't ETHERTYPE_IP: */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, NDBOOTD_OFFSETOF(struct ether_header, ether_type)),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 9),

	/* drop this packet if its IP protocol isn't IPPROTO_ND: */
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, sizeof(struct ether_header) + NDBOOTD_OFFSETOF(struct ip, ip_p)),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_ND, 0, 7),

	/* drop this packet if it's a fragment: */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, sizeof(struct ether_header) + NDBOOTD_OFFSETOF(struct ip, ip_off)),
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x3fff, 5, 0),

	/* drop this packet if it is carrying data (we only want requests,
	 * which have no data): */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, sizeof(struct ether_header) + NDBOOTD_OFFSETOF(struct ip, ip_len)),
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, sizeof(struct ether_header)),
	BPF_STMT(BPF_ALU + BPF_SUB + BPF_X, 0),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct ndboot_packet), 0, 1),

	/* accept this packet: */
	BPF_STMT(BPF_RET + BPF_K, (u_int) -1),

	/* drop this packet: */
	BPF_STMT(BPF_RET + BPF_K, 0),
};

/* this opens a raw socket using BPF. */
int
ndbootd_raw_open(struct ndbootd_interface * interface)
{
	int network_fd;
#define DEV_BPF_FORMAT "/dev/bpf%d"
	char dev_bpf_filename[sizeof(DEV_BPF_FORMAT) + (sizeof(int) * 3) + 1];
	int minor;
	int saved_errno;
	u_int bpf_opt;
	struct bpf_version version;
	u_int packet_buffer_size;
	struct bpf_program program;
	struct _ndbootd_interface_bpf *interface_bpf;

	/* loop trying to open a /dev/bpf device: */
	for (minor = 0;; minor++) {

		/* form the name of the next device to try, then try opening
		 * it. if we succeed, we're done: */
		sprintf(dev_bpf_filename, DEV_BPF_FORMAT, minor);
		_NDBOOTD_DEBUG((fp, "bpf: trying %s", dev_bpf_filename));
		if ((network_fd = open(dev_bpf_filename, O_RDWR)) >= 0) {
			_NDBOOTD_DEBUG((fp, "bpf: opened %s", dev_bpf_filename));
			break;
		}
		/* we failed to open this device.  if this device was simply
		 * busy, loop: */
		_NDBOOTD_DEBUG((fp, "bpf: failed to open %s: %s", dev_bpf_filename, strerror(errno)));
		if (errno == EBUSY) {
			continue;
		}
		/* otherwise, we have failed: */
		return (-1);
	}

	/* this macro helps in closing the BPF socket on error: */
#define _NDBOOTD_RAW_OPEN_ERROR(x) saved_errno = errno; x; errno = saved_errno

	/* check the BPF version: */
	if (ioctl(network_fd, BIOCVERSION, &version) < 0) {
		_NDBOOTD_DEBUG((fp, "bpf: failed to get the BPF version on %s: %s",
			dev_bpf_filename, strerror(errno)));
		_NDBOOTD_RAW_OPEN_ERROR(close(network_fd));
		return (-1);
	}
	if (version.bv_major != BPF_MAJOR_VERSION
	    || version.bv_minor < BPF_MINOR_VERSION) {
		_NDBOOTD_DEBUG((fp, "bpf: kernel BPF version is %d.%d, my BPF version is %d.%d",
			version.bv_major, version.bv_minor,
			BPF_MAJOR_VERSION, BPF_MINOR_VERSION));
		close(network_fd);
		errno = ENXIO;
		return (-1);
	}
	/* put the BPF device into immediate mode: */
	bpf_opt = TRUE;
	if (ioctl(network_fd, BIOCIMMEDIATE, &bpf_opt) < 0) {
		_NDBOOTD_DEBUG((fp, "bpf: failed to put %s into immediate mode: %s",
			dev_bpf_filename, strerror(errno)));
		_NDBOOTD_RAW_OPEN_ERROR(close(network_fd));
		return (-1);
	}
	/* tell the BPF device we're providing complete Ethernet headers: */
	bpf_opt = TRUE;
	if (ioctl(network_fd, BIOCSHDRCMPLT, &bpf_opt) < 0) {
		_NDBOOTD_DEBUG((fp, "bpf: failed to put %s into complete-headers mode: %s",
			dev_bpf_filename, strerror(errno)));
		_NDBOOTD_RAW_OPEN_ERROR(close(network_fd));
		return (-1);
	}
	/* point the BPF device at the interface we're using: */
	if (ioctl(network_fd, BIOCSETIF, interface->ndbootd_interface_ifreq) < 0) {
		_NDBOOTD_DEBUG((fp, "bpf: failed to point BPF socket at %s: %s",
			interface->ndbootd_interface_ifreq->ifr_name, strerror(errno)));
		saved_errno = errno;
		close(network_fd);
		errno = saved_errno;
		return (-1);
	}
	/* set the filter on the BPF device: */
	program.bf_len = sizeof(ndboot_bpf_filter) / sizeof(ndboot_bpf_filter[0]);
	program.bf_insns = ndboot_bpf_filter;
	if (ioctl(network_fd, BIOCSETF, &program) < 0) {
		_NDBOOTD_DEBUG((fp, "bpf: failed to set the filter on %s: %s",
			dev_bpf_filename, strerror(errno)));
		_NDBOOTD_RAW_OPEN_ERROR(close(network_fd));
		return (-1);
	}
	/* get the BPF read buffer size: */
	if (ioctl(network_fd, BIOCGBLEN, &packet_buffer_size) < 0) {
		_NDBOOTD_DEBUG((fp, "bpf: failed to read the buffer size for %s: %s",
			dev_bpf_filename, strerror(errno)));
		_NDBOOTD_RAW_OPEN_ERROR(close(network_fd));
		return (-1);
	}
	_NDBOOTD_DEBUG((fp, "bpf: buffer size for %s is %u",
		dev_bpf_filename, packet_buffer_size));

	/* allocate our private interface information and we're done: */
	interface->ndbootd_interface_fd = network_fd;
	interface_bpf = ndbootd_new0(struct _ndbootd_interface_bpf, 1);
	interface_bpf->_ndbootd_interface_bpf_buffer_size = packet_buffer_size;
	interface_bpf->_ndbootd_interface_bpf_buffer = ndbootd_new(char, packet_buffer_size);
	interface->_ndbootd_interface_raw_private = interface_bpf;
	return (0);
#undef _NDBOOTD_RAW_OPEN_ERROR
}

/* this reads a raw packet: */
int
ndbootd_raw_read(struct ndbootd_interface * interface, void *packet_buffer, size_t packet_buffer_size)
{
	struct _ndbootd_interface_bpf *interface_bpf;
	ssize_t buffer_end;
	struct bpf_hdr the_bpf_header;
	fd_set fdset_read;

	/* recover our state: */
	interface_bpf = (struct _ndbootd_interface_bpf *) interface->_ndbootd_interface_raw_private;

	/* loop until we have something to return: */
	for (;;) {

		/* if the buffer is empty, fill it: */
		if (interface_bpf->_ndbootd_interface_bpf_buffer_offset
		    >= interface_bpf->_ndbootd_interface_bpf_buffer_end) {

			/* select on the BPF socket: */
			_NDBOOTD_DEBUG((fp, "bpf: calling select"));
			FD_ZERO(&fdset_read);
			FD_SET(interface->ndbootd_interface_fd, &fdset_read);
			switch (select(interface->ndbootd_interface_fd + 1, &fdset_read, NULL, NULL, NULL)) {
			case 0:
				_NDBOOTD_DEBUG((fp, "bpf: select returned zero"));
				continue;
			case 1:
				break;
			default:
				if (errno == EINTR) {
					_NDBOOTD_DEBUG((fp, "bpf: select got EINTR"));
					continue;
				}
				_NDBOOTD_DEBUG((fp, "bpf: select failed: %s", strerror(errno)));
				return (-1);
			}
			assert(FD_ISSET(interface->ndbootd_interface_fd, &fdset_read));

			/* read the BPF socket: */
			_NDBOOTD_DEBUG((fp, "bpf: calling read"));
			buffer_end = read(interface->ndbootd_interface_fd,
			    interface_bpf->_ndbootd_interface_bpf_buffer,
			    interface_bpf->_ndbootd_interface_bpf_buffer_size);
			if (buffer_end <= 0) {
				_NDBOOTD_DEBUG((fp, "bpf: failed to read packets: %s", strerror(errno)));
				return (-1);
			}
			_NDBOOTD_DEBUG((fp, "bpf: read %d bytes of packets", buffer_end));
			interface_bpf->_ndbootd_interface_bpf_buffer_offset = 0;
			interface_bpf->_ndbootd_interface_bpf_buffer_end = buffer_end;
		}
		/* if there's not enough for a BPF header, flush the buffer: */
		if ((interface_bpf->_ndbootd_interface_bpf_buffer_offset
			+ sizeof(the_bpf_header))
		    > interface_bpf->_ndbootd_interface_bpf_buffer_end) {
			_NDBOOTD_DEBUG((fp, "bpf: flushed garbage BPF header bytes"));
			interface_bpf->_ndbootd_interface_bpf_buffer_end = 0;
			continue;
		}
		/* get the BPF header and check it: */
		memcpy(&the_bpf_header,
		    interface_bpf->_ndbootd_interface_bpf_buffer
		    + interface_bpf->_ndbootd_interface_bpf_buffer_offset,
		    sizeof(the_bpf_header));
		interface_bpf->_ndbootd_interface_bpf_buffer_offset += the_bpf_header.bh_hdrlen;

		/* if we're missing some part of the packet: */
		if (the_bpf_header.bh_caplen != the_bpf_header.bh_datalen
		    || ((interface_bpf->_ndbootd_interface_bpf_buffer_offset + the_bpf_header.bh_datalen)
			> interface_bpf->_ndbootd_interface_bpf_buffer_end)) {
			_NDBOOTD_DEBUG((fp, "bpf: flushed truncated BPF packet"));
			interface_bpf->_ndbootd_interface_bpf_buffer_offset += the_bpf_header.bh_datalen;
			continue;
		}
		/* silently ignore packets that don't even have Ethernet
		 * headers, and those packets that we transmitted: */
		if (the_bpf_header.bh_datalen < sizeof(struct ether_header)
		    || !memcmp(((struct ether_header *)
			    (interface_bpf->_ndbootd_interface_bpf_buffer
				+ interface_bpf->_ndbootd_interface_bpf_buffer_offset))->ether_shost,
			interface->ndbootd_interface_ether,
			ETHER_ADDR_LEN)) {
			/* silently ignore packets from us: */
			interface_bpf->_ndbootd_interface_bpf_buffer_offset += the_bpf_header.bh_datalen;
			continue;
		}
		/* if the caller hasn't provided a large enough buffer: */
		if (packet_buffer_size < the_bpf_header.bh_datalen) {
			errno = EIO;
			interface_bpf->_ndbootd_interface_bpf_buffer_offset += the_bpf_header.bh_datalen;
			return (-1);
		}
		/* return this captured packet to the user: */
		memcpy(packet_buffer,
		    interface_bpf->_ndbootd_interface_bpf_buffer
		    + interface_bpf->_ndbootd_interface_bpf_buffer_offset,
		    the_bpf_header.bh_datalen);
		interface_bpf->_ndbootd_interface_bpf_buffer_offset += the_bpf_header.bh_datalen;
		return (the_bpf_header.bh_datalen);
	}
	/* NOTREACHED */
}

/* this writes a raw packet: */
int
ndbootd_raw_write(struct ndbootd_interface * interface, void *packet_buffer, size_t packet_buffer_size)
{
	return (write(interface->ndbootd_interface_fd, packet_buffer, packet_buffer_size));
}