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Rework UDP parsing, particularly around IP addresses.

This originally started as trying to put a consistent space between
the UDP header information and the payload parsing, but while doing
that I noticed inconsistent IPv4 vs IPv6 handling.

Apart from the default "srcip.srcport > dstip.dstpor" output, all
the other places that IP addresses were printed assumed IPv4. It
looks like it is possible that udp_print() can be called without
an IP header, which made these blind IPv4 prints turn into NULL
derefs.

This fixes the problem above by only having a single place that
prints the addresses out, and makes sure to get the difference
between IPv4, IPv6 and no IP correct.

This changes how the checksum is calculated. It incrementally builds
the UDP checksum by feeding the IPv4 and v6 addresses in separately,
then using common code for the rest of the pseudo header and actual
payload.

Lastly, this does make printing the space between the UDP header
and its payload consistent. The UDP code is now responsible for
adding a space after itself so the payload parsers don't have to.
They got it wrong in some cases anyway, so this should be a lot
more uniform.

help and ok sthen@

/*	$OpenBSD: print-iapp.c,v 1.6 2018/07/06 05:47:22 dlg Exp $	*/

/*
 * Copyright (c) 2005 Reyk Floeter <reyk@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/time.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>

#include <net/if.h>

#include <netinet/in.h>
#include <netinet/if_ether.h>

#include <net80211/ieee80211.h>

#include <pcap.h>
#include <stdio.h>
#include <string.h>

#include "addrtoname.h"
#include "interface.h"
#include "iapp.h"

const char *ieee80211_iapp_frame_type_name[] =
    IEEE80211_IAPP_FRAME_TYPE_NAME;

extern int ieee80211_encap;

void
iapp_print(const u_char *p, u_int len)
{
	struct ieee80211_iapp_frame *wf = (struct ieee80211_iapp_frame *)p;
	struct ieee80211_iapp_add_notify *add;
	struct pcap_pkthdr fakeh;
	const u_char *data;

	TCHECK2(*wf, sizeof(struct ieee80211_iapp_frame));

	/* Print common IAPP information */
	printf("IAPPv%u ", wf->i_version);
	if (wf->i_command & 0xf0)
		printf("unknown: 0x%0x ", wf->i_command);
	else
		printf("%s ", ieee80211_iapp_frame_type_name[wf->i_command]);
	printf("(id %u) %u: ", wf->i_identifier, wf->i_length);


	data = p + sizeof(struct ieee80211_iapp_frame);

	switch (wf->i_command) {
	case IEEE80211_IAPP_FRAME_ADD_NOTIFY:
		/*
		 * Print details about the IAPP ADD.notify message.
		 */
		TCHECK2(*data, sizeof(struct ieee80211_iapp_add_notify));
		add = (struct ieee80211_iapp_add_notify *)data;

		printf("octets %u, ", add->a_length);
		if (add->a_reserved)
			printf("reserved %u, ", add->a_reserved);
		if (add->a_length == IEEE80211_ADDR_LEN)
			printf("lladdr %s, ", etheraddr_string(add->a_macaddr));
		printf("seq %u", add->a_seqnum);
		break;
	case IEEE80211_IAPP_FRAME_HOSTAPD_RADIOTAP:
	case IEEE80211_IAPP_FRAME_HOSTAPD_PCAP:
		/*
		 * hostapd(8) uses its own subtypes to send IEEE 802.11
		 * frame dumps to the IAPP group (either with or without
		 * radiotap header). Decode it using the IEEE 802.11
		 * printer.
		 */
		bzero(&fakeh, sizeof(fakeh));
		fakeh.len = wf->i_length;
		fakeh.caplen = snapend - data;

		ieee80211_encap = 1;
		if (wf->i_command == IEEE80211_IAPP_FRAME_HOSTAPD_RADIOTAP)
			ieee802_11_radio_if_print(NULL, &fakeh, data);
		else
			ieee802_11_if_print(NULL, &fakeh, data);
		ieee80211_encap = 0;
		break;
	}
	return;

trunc:
	printf("[|IAPP]");
}