Hey all,
and here comes the third resubmission of my patches. I do still
believe that they are improvements. Even one year after writing
them, them do still apply cleanly on the master branch.
Best,
Dominik
Forwarded Message
From: Dominik Derigs
To: dnsmasq-discuss@lists.thekelleys.org.uk
, Simon Kelley
Subject: Fwd: [PATCH] Addressing hostsdir shortcomings
Date: Sat, 02 Apr 2022 21:32:30 +0200
Dear Simon,
Second resubmission of my patches.
They still apply cleanly to current master.
Best,
Dominik
Forwarded Message
From: Dominik Derigs
To: dnsmasq-discuss@lists.thekelleys.org.uk
, Simon Kelley
Subject: [PATCH] Addressing hostsdir shortcomings
Date: Sat, 08 Jan 2022 11:45:32 +0100
Hey Simon,
dnsmasq v2.73 added --hostsdir which is an efficient way of re-
loading only parts of the cache. When we tried to use hostsdir
yesterday, we identified three problems. They are described
below. Patches addressing them are attached.
--- ISSUE 1 --- Logging imprecision
Assume you have multiple files in hostsdir, dnsmasq can only log
the directory not the file that was the real source:
dnsmasq: read /home/test/hostsdir/hosts1 - 1 addresses
dnsmasq: read /home/test/hostsdir/hosts2 - 1 addresses
dnsmasq: read /home/test/hostsdir/hosts3 - 1 addresses
dnsmasq: 1 127.0.0.1/34170 query[A] aaa from 127.0.0.1
dnsmasq: 1 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 1 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.1
dnsmasq: 1 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
This happens because the cache entries all use the same index
that is the directory name.
--- ISSUE 2 --- Outdated entries are not removed
When hostsdir re-reads the file, it does not remove outdated
entries. Assume you modify "192.168.1.1 aaa" to "192.168.1.2
aaa", dnsmasq will now serve two A records for "aaa". This may be
considered okay, however, if I add "192.168.1.1 bbb", PTR
requests for this domain will still be replied with "aaa" which
might be completely outdated information.
--- ISSUE 3 --- Ever growing replies under certain situations
When a users uses an editor that creates (temporary) files during
editing (like "sed -i") or uses a script that writes files line
by line (like "echo '' >> file"), they can quickly end up with
strange things like
dnsmasq: 3 127.0.0.1/34170 query[A] aaa from 127.0.0.1
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.1
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
dnsmasq: 3 127.0.0.1/34170 /home/test/hostsdir aaa is 192.168.1.2
which is not very meaningful. We check for duplicates before
inserting into the cache, however, duplicate checking can be
foiled here: add_hosts_entry() calls cache_find_by_name() only
once (say it returned "192.168.1.1") so the memcmp() on the
address fails and we can add an arbitrary amount of 192.168.1.2
entries.
For addressing issue 1, I added a new struct *dyndir having a
linked list of struct *hostsfile. With this, cache_insert() can
get the correct index. If a file is newly added, we just add a
new *hostsfile entry to the list (index++).
Issue 2 is an easy one as we can selectively clean the cache when
we know the uid to be removed. This can be called before running
read_hostsfile() to insert new stuff. I added MOVE_FROM and
DELETE to inotify_add_watch() so we catch if a file was removed.
In this case, we only remove old entries.
Issue 3 is fixed by adding a loop over cache_find_by_name() in
add_hosts_entry() to check possible multiple records.
Best,
Dominik
[sent earlier as
https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2021q3/015704.html
,
resubmitting patches rebased on latest master]
From 7873cc3dbfce3edeb534bf4d0a0030894aaa152a Mon Sep 17 00:00:00 2001
From: Dominik Derigs
Date: Wed, 29 Sep 2021 08:22:05 +0200
Subject: [PATCH 1/3] Extend hostsdir to store the individual files as sources
for loggin
Signed-off-by: DL6ER
---
src/cache.c | 9 +++--
src/dnsmasq.h | 13 ++-
src/inotify.c | 103 ++
src/option.c | 40
4 files changed, 111 insertions(+), 54 deletions(-)
diff --git a/src/cache.c b/src/cache.c
index 246c3f2..e86d69b 100644
--- a/src/cache.c
+++ b/src/cache.c
@@ -1839,6 +1839,7 @@ void dump_cache(time_t now)
char *record_source(unsigned int index)
{
struct hostsfile *ah;
+ struct dyndir *dd;
if (index == SRC_CONFIG)
return "config";
@@ -1850,9 +1851,11 @@ char *record_source(unsigned int index)
return ah->fname;
#ifdef HAVE_INOTIFY
- for
