mirror of
https://gitlab.isc.org/isc-projects/bind9
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58bd26b6cf
This commit converts the license handling to adhere to the REUSE specification. It specifically: 1. Adds used licnses to LICENSES/ directory 2. Add "isc" template for adding the copyright boilerplate 3. Changes all source files to include copyright and SPDX license header, this includes all the C sources, documentation, zone files, configuration files. There are notes in the doc/dev/copyrights file on how to add correct headers to the new files. 4. Handle the rest that can't be modified via .reuse/dep5 file. The binary (or otherwise unmodifiable) files could have license places next to them in <foo>.license file, but this would lead to cluttered repository and most of the files handled in the .reuse/dep5 file are system test files.
127 lines
4.0 KiB
Plaintext
127 lines
4.0 KiB
Plaintext
<!--
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Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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SPDX-License-Identifier: MPL-2.0
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This Source Code Form is subject to the terms of the Mozilla Public
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License, v. 2.0. If a copy of the MPL was not distributed with this
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file, you can obtain one at https://mozilla.org/MPL/2.0/.
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See the COPYRIGHT file distributed with this work for additional
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information regarding copyright ownership.
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-->
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You are lost in a maze of twisty little pointers, all alike...
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ADB |-> 0 |-> handle ---> handle ---> 0
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|-lists of names --------> name -------> name -------> 0
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| namehook namehook
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| | 0 0 -> fetch
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| V
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|-lists of elements -----> element ----> element ----> element ---> 0
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| | | |
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| |-> zoneinfo |-> 0 |-> zoneinfo
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|-lists of dead handles
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...
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A handle contains a task, taskaction, and event argument, and is linkable
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in two ways. One, for the list returned to the caller, and two to be
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attached to either a name (so events can be generated) or to the dead handle
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list, where no events are generated.
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HANDLE
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|--- addrinfo ---> addrinfo ---> 0
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| |-> entry |-> entry
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|--- task, action, arg
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V
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HANDLE
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V
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0
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Notes and questions:
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o If a handle is on the dead handle list, it is only waiting for
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the caller to dns_adb_done() it.
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o If a handle is on a name list, it will generate at most one
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event, and then be moved to the dead handle list.
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o If events are not requested, it is NEVER placed on the name's
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list, even though fetches for that name may be started.
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o Names will have to have a reference count for each fetch
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in progress. They will also have a bit that says some
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previous fetches failed. XXX How in the world would I
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"refresh" the data? If I only got 2 of 9 A6 chains to converge,
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when and how do I restart them later?
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o The caller will give us a name, and we will return two items:
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a handle and a list of addresses. If the list was non-empty when
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it was given to us, we will append (unique) addrinfo's to the list.
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o How in the world do you shut this thing down?
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If you cancel the fetches first:
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1. The handles are sent an event saying "no more
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names are coming."
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2. The handles are moved to the dead handle list.
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If you cancel the handles first:
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1. The handles are moved to the dead handle list.
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It would therefore seem simpler to cancel/done all handles first,
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then all fetches.
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o If a fetch returns a CNAME, what do we do?
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o If a fetch returns a DNAME, what do we do?
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o If a fetch returns 4 ipv4 addresses, we will have to allocate
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3 more (total of 4) namehooks, 4 entries, and fill them in.
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What happens if only some of these can be allocated?
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o ipv6 raises the memory problem to a new level. What if we
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have to fork into multiple chains, but we run out of memory?
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----------------------------------------------------------------------
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Looking up entries via names:
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Look for the name in the database.
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FOUND:
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For each complete address, allocate an addrinfo structure
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and add it to the handle.
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If any fetches are in progress for this name, attach this
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handle to this name so events can be posted to the handle,
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if the handle wants events.
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If no fetches are in progress and the name is incomplete,
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see if we can start a fetch for this name.
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NOT FOUND:
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Create a new adbname structure.
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Create a new namehook structure.
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Start a fetch on this name.
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If more data is coming (fetches are in progress) attach
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the handle to the name, so it can get notification of
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new data.
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If the name is incomplete (due to fetches in progress,
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recently failed fetches, or the inability to start new
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fetches) copy the incomplete flag to the handle, so the
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caller can know this.
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