/*
 * netsniff-ng - the packet sniffing beast
 * Copyright 2012 Markus Amend <markus@netsniff-ng.org>, Deutsche Flugsicherung GmbH
 * Subject to the GPL, version 2.
 *
 * IPv6 Hop-By-Hop Header described in RFC2460
 */

#include <stdio.h>
#include <stdint.h>
#include <netinet/in.h>    /* for ntohs() */

#include "proto.h"
#include "dissector_eth.h"
#include "built_in.h"
#include "pkt_buff.h"

struct hop_by_hophdr {
	uint8_t h_next_header;
	uint8_t hdr_len;
} __packed;

static void dissect_opt_hop(struct pkt_buff *pkt __maybe_unused,
			    ssize_t *opt_len)
{
	/* Have to been upgraded.
	 * http://tools.ietf.org/html/rfc2460#section-4.2
	 * Look also for proto_ipv6_dest_opts.h, it needs
	 * dissect_opt(), too.
	 */
	if (*opt_len)
		tprintf(", Option(s) recognized ");

	/* If adding dissector reduce opt_len for each using of pkt_pull
	 * to the same size.
	 */
}

static void hop_by_hop(struct pkt_buff *pkt)
{
	uint16_t hdr_ext_len;
	ssize_t opt_len;
	struct hop_by_hophdr *hop_ops;

	hop_ops = (struct hop_by_hophdr *) pkt_pull(pkt, sizeof(*hop_ops));
	if (hop_ops == NULL)
		return;

	/* Total Header Length in Bytes */
	hdr_ext_len = (hop_ops->hdr_len + 1) * 8;
	/* Options length in Bytes */
	opt_len = hdr_ext_len - sizeof(*hop_ops);

	tprintf("\t [ Hop-by-Hop Options ");
	tprintf("NextHdr (%u), ", hop_ops->h_next_header);
	if (opt_len > pkt_len(pkt) || opt_len < 0){
		tprintf("HdrExtLen (%u, %u Bytes, %s)", hop_ops->hdr_len,
		      hdr_ext_len, colorize_start_full(black, red)
		      "invalid" colorize_end());
		      return;
	}
	tprintf("HdrExtLen (%u, %u Bytes)", hop_ops->hdr_len,
		hdr_ext_len);

	dissect_opt_hop(pkt, &opt_len);

	tprintf(" ]\n");

	pkt_pull(pkt, opt_len);
	pkt_set_dissector(pkt, &eth_lay3, hop_ops->h_next_header);
}

static void hop_by_hop_less(struct pkt_buff *pkt)
{
	uint16_t hdr_ext_len;
	ssize_t opt_len;
	struct hop_by_hophdr *hop_ops;

	hop_ops = (struct hop_by_hophdr *) pkt_pull(pkt, sizeof(*hop_ops));
	if (hop_ops == NULL)
		return;

	/* Total Header Length in Bytes */
	hdr_ext_len = (hop_ops->hdr_len + 1) * 8;
	/* Options length in Bytes */
	opt_len = hdr_ext_len - sizeof(*hop_ops);
	if (opt_len > pkt_len(pkt) || opt_len < 0)
		return;

	tprintf(" Hop Ops");

	pkt_pull(pkt, opt_len);
	pkt_set_dissector(pkt, &eth_lay3, hop_ops->h_next_header);
}

struct protocol ipv6_hop_by_hop_ops = {
	.key = 0x0,
	.print_full = hop_by_hop,
	.print_less = hop_by_hop_less,
};
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<div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Filipe Manana &lt;fdmanana@suse.com&gt;</td><td class='right'>2016-05-12 13:53:36 +0100</td></tr>
<tr><th>committer</th><td>Filipe Manana &lt;fdmanana@suse.com&gt;</td><td class='right'>2016-05-13 01:59:36 +0100</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af'>5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af</a> (<a href='/cgit.cgi/linux/net-next.git/patch/?id=5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af'>d97a7f5d321694e09c3046e9027c23a02d6a5878</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=f78c436c3931e7df713688028f2b4faf72bf9f2a'>f78c436c3931e7df713688028f2b4faf72bf9f2a</a> (<a href='/cgit.cgi/linux/net-next.git/diff/?id=5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af&amp;id2=f78c436c3931e7df713688028f2b4faf72bf9f2a'>diff</a>)</td></tr></table>
<div class='commit-subject'>Btrfs: add semaphore to synchronize direct IO writes with fsync</div><div class='commit-msg'>Due to the optimization of lockless direct IO writes (the inode's i_mutex
is not held) introduced in commit 38851cc19adb ("Btrfs: implement unlocked
dio write"), we started having races between such writes with concurrent
fsync operations that use the fast fsync path. These races were addressed
in the patches titled "Btrfs: fix race between fsync and lockless direct
IO writes" and "Btrfs: fix race between fsync and direct IO writes for
prealloc extents". The races happened because the direct IO path, like
every other write path, does create extent maps followed by the
corresponding ordered extents while the fast fsync path collected first
ordered extents and then it collected extent maps. This made it possible
to log file extent items (based on the collected extent maps) without
waiting for the corresponding ordered extents to complete (get their IO
done). The two fixes mentioned before added a solution that consists of
making the direct IO path create first the ordered extents and then the
extent maps, while the fsync path attempts to collect any new ordered
extents once it collects the extent maps. This was simple and did not
require adding any synchonization primitive to any data structure (struct
btrfs_inode for example) but it makes things more fragile for future
development endeavours and adds an exceptional approach compared to the
other write paths.

This change adds a read-write semaphore to the btrfs inode structure and
makes the direct IO path create the extent maps and the ordered extents
while holding read access on that semaphore, while the fast fsync path
collects extent maps and ordered extents while holding write access on
that semaphore. The logic for direct IO write path is encapsulated in a
new helper function that is used both for cow and nocow direct IO writes.

Signed-off-by: Filipe Manana &lt;fdmanana@suse.com&gt;
Reviewed-by: Josef Bacik &lt;jbacik@fb.com&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af'>Diffstat</a></div><table summary='diffstat' class='diffstat'>