intialization when recording using the proc method

add new METADATA sections only if they differ from
the previous ones

fixes #347

Change-Id: I32ef9efa674e74c3a1263c0fd786a16562ea7838

Valid options are raw and eth. Default is raw as it was before last commit.
fixes #290

Change-Id: I8102144ab1508fe815be84d727f6fa3234fd0994

fixes #288

Change-Id: I628643914cd1f41081ffef0018628b1b38348719

Squashed commit of the following:

commit 1af3efd464
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Nov 7 11:10:22 2016 -0500

    save and restore call recording status to/from redis

    closes #254

    Change-Id: If3cd34fcfd64fa8164521a86eb1d1aa0eb327f3b

commit 460053a231
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Nov 4 14:09:08 2016 -0400

    restore libcurl build dependency

    Change-Id: Ia853f928caf9e443bb69c4015cbba805e6d24153

commit 5f5fd88fde
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Nov 4 11:22:27 2016 -0400

    ensure we are always decrypting SRTP when recording

    Change-Id: I2b75afefcadc55ebf1bf6a19a983134c87c41602

commit 69b4e9fa88
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Nov 4 09:56:47 2016 -0400

    remove redundant ng result=ok logic

    Change-Id: I84d7245f52dc12a4002b4dd2b736afea9ae733fa

commit 411213dd3d
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Nov 3 16:04:54 2016 -0400

    support the `start recording` command message

    Change-Id: I316e90fd3fe34f01b20826936ef620bcff785397

commit ae1910c68d
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Nov 3 15:01:57 2016 -0400

    move logic for `record call` flag to where it belongs

    Change-Id: I65a3b5d62f4360df4251faea1339b5a6355c0e6d

commit 217008d572
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Nov 3 12:49:48 2016 -0400

    support combining streams into one pcap in reference scripts

    Change-Id: Id82936ae7ef1b406acf3b4d3429ecc1cb6e2356e

commit 3fcafd9275
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Nov 3 11:40:00 2016 -0400

    output additional details to metafiles

    Change-Id: I0539a0617aff51c9c499bbd9586d61c7e7ca7e7c

commit e81f413f3b
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Nov 2 16:18:28 2016 -0400

    globalize kernel access variables

    Change-Id: Ie07e0ebb8705189c8b1e49f596080ff8bcaef64f

commit 5e74609c7c
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Nov 2 12:20:55 2016 -0400

    duplicate error messages to stderr when in foreground

    Change-Id: Iaf9d8d1392946046846cb6f2c0fb928a96893911

commit 032077bed4
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Nov 2 11:38:22 2016 -0400

    eliminate dummy virtual function

    Change-Id: I7cc2596f31350bf0d39253b3bd7e9fe1cec2b92d

commit 9177effc4e
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Nov 2 11:30:58 2016 -0400

    clean up recording code related to ng interface

    Change-Id: I69c6d953f8467e5154f000979c94f2dc3a79918a

commit ac0ec6a5e7
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Nov 2 10:57:15 2016 -0400

    output before/after sdp to metafiles

    Change-Id: I1d3177e40591d6b4c4789eb6e18132743a9eda45

commit 68b27fa964
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Nov 1 15:40:20 2016 -0400

    fix header length problems

    Change-Id: I896453f72df3ba146251f5d82ca1d02dd0ad08e9

commit ebbd942ad0
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Nov 1 14:14:08 2016 -0400

    support writing pcap files in reference intercept script

    Change-Id: I53502ba416426e9012a68c35cdf4b457d7c3eb69

commit fe82efa40a
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Nov 1 13:35:47 2016 -0400

    ensure we never make any calls that might sleep when holding locks

    Change-Id: I1ce6aeced1f61715374b80f6fb1fbeafc987ae7f

commit be5316e804
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Nov 1 13:08:19 2016 -0400

    fix math in auto_array_find_free_index

    Change-Id: I39c786b03dbafe59b88a1945ac27964c3852c9eb

commit 183d4939ca
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Nov 1 11:41:47 2016 -0400

    adding rudimentary lock debugging

    Change-Id: Iff541c58e5ea4c3fc2ec16e93396148f935bc4f3

commit 51a75c5022
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Oct 31 14:35:17 2016 -0400

    handle read errors in reference intercept script

    Change-Id: I047d763dbd498026a0d8db24c5532155c75fd6e6

commit 69a460de08
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Oct 31 14:34:54 2016 -0400

    changed locking semantics to avoid proc_clear deadlock

    Change-Id: I70dbc07aa8af7b9860beca86b4b82d8180d8a0ae

commit 62eae1459a
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Oct 31 12:50:26 2016 -0400

    additional debugging

    Change-Id: I81c93c2dd9007ed6a0d6e0b147de0deb44b7b023

commit fd36794740
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Oct 28 12:07:25 2016 -0400

    adding reference implementation using inotify

    Change-Id: Ibec73bdc4c7a576e4beaf5e749567dd2508be4df

commit f8fde6cc73
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Oct 27 15:55:10 2016 -0400

    add stream info to metadata files

    Change-Id: I200df14a3e35c2c0077866444b96692de4303761

commit 5a8b4dd156
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Oct 27 14:47:49 2016 -0400

    pass intercepted packets to kernel and tie in kernel idx

    Change-Id: I33ff297c4a66276b05d0e5d537b0281f27116243

commit 0c0b97ea39
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Oct 27 12:29:02 2016 -0400

    abstractize fake packet header and support ipv6

    Change-Id: I6c1ad1cccad306f3d306fb3387efcb033a3574b2

commit e1b648b9ba
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Oct 27 09:32:40 2016 -0400

    support creating kernel intercept streams

    Change-Id: I1f9bdda61af52814f07f765a8b558a7491cfc0b9

commit b6737ec963
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Oct 26 14:46:13 2016 -0400

    get rid of call->record_call flag

    Change-Id: I04dcba49b07fc669b0bb4bcea8ccc2b52cb76e02

commit 6ed362c120
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Oct 26 12:53:04 2016 -0400

    add recorded call to /proc

    Change-Id: I1fe64b9fb8fe3604bb7d432899c43e3e37ea6a4f

commit 62d2508ecf
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Oct 26 10:10:05 2016 -0400

    simplify some code

    Change-Id: I2a27400e91f58aa8ea20d3e610a7509d2e9a0dfc

commit 0c811a8e91
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Oct 25 16:12:59 2016 -0400

    create separate ../tmp recording dir and clean up duplicate code

    Change-Id: I94e0c19a1e8fed5a30212b79930987333f5e6786

commit 16592a9230
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Oct 25 11:26:54 2016 -0400

    remove explicit libcurl dependency

    finally properly fixes #251

    Change-Id: I3feafe2d0086f6dd789175e6ec0079c54edd487a

commit c78ac5bbb7
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Oct 25 10:48:50 2016 -0400

    abstractize recording cleanup routine

    Change-Id: Ib9fc46542f273bab53f611a1456f02d67edfc966

commit d8358c9a2c
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Oct 25 10:07:44 2016 -0400

    use shorthand for function pointers

    Change-Id: Idf43949e20281a10317e22a5b68a6d133e398bd4

commit 9417437c10
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Oct 24 15:31:56 2016 -0400

    abstractize individual recording functions

    Change-Id: I0974696b6bb361fce39b24d6be91b5c052ee2b14

commit eb631cd876
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Oct 24 11:54:42 2016 -0400

    abstractize call recording mechanism

    Change-Id: If8672051227944544d9cf916d359c5db67235e3e

commit 70797ceb8f
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Jul 14 11:25:05 2016 -0400

    combine two mallocs into one for user-generated packets

    Change-Id: I585d129f10d379a5cb853382773f91a7cec9a98d

commit f62f71cee4
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 13 14:22:18 2016 -0400

    check for and avoid /proc file name collisions

    Change-Id: Ie9eb9ceef8f32de8aba816f0121e768c57fa7402

commit ec6b3d22fc
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 13 11:02:04 2016 -0400

    implement free list

    Change-Id: I3e7dc2325c937923d19ce6000f2cf1c011e51037

commit bd75a1cf25
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 13 09:30:36 2016 -0400

    make number of packets retained per stream configurable

    Change-Id: If1c87f80dd7367cbc274d13c15f94836ef9c8cb1

commit de259c3d64
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Jul 12 15:15:01 2016 -0400

    facilitate passing packets from kernel module out to userspace

    Change-Id: I2317a007084a1718e185ba04632c53a9ebe5f29d

commit 3aa88716fb
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Mon Jul 11 10:45:10 2016 -0400

    restructure calls and streams to global arrays

    Change-Id: Icfca615b21f2e51b1abda4422c4eeb8f4ac70a9b

commit 6cf9980f3e
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Jul 8 11:53:32 2016 -0400

    implement poll/select mechanism

    Change-Id: Ic10c017250f0991f691a887b078e80f694bba853

commit d95829e07b
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Jul 8 10:44:38 2016 -0400

    discard new/old packets as required

    Change-Id: If73ce77dcbc24addb6ce0931b90de0f5efae9f51

commit be1d769e44
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Fri Jul 8 10:25:38 2016 -0400

    implement EOF for stream readers

    Change-Id: I858dc1fdd7df3b65283e1d96457d87e7452840f5

commit ed2d98d55a
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Jul 7 15:02:58 2016 -0400

    blocking and nonblocking reads - incomplete

    Change-Id: I7cbfb09507ad8726773d6a28ddb98d5981decd04

commit 246709c7f4
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Jul 7 13:55:41 2016 -0400

    rudimentary packet reading/dequeuing

    Change-Id: I1a924e5cb2ef4e4f16aeff1f1dd90d0746f91da5

commit 4277493949
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Jul 7 12:40:31 2016 -0400

    use kzalloc where appropriate

    Change-Id: Icd6a109a69ab4f6dc9f7d35fd9e8fc9127f8e7e0

commit 5b07819217
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Jul 7 09:07:54 2016 -0400

    more module referencing

    Change-Id: I2e34fe74f2edef9170a4558f6a24394240966d79

commit 1d8268f636
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 6 14:56:42 2016 -0400

    store delivered packets in queue

    Change-Id: Id349b75e06f9dd77c884196b7726027ac5cab7ae

commit 23c6a53f94
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 6 14:21:27 2016 -0400

    implement call for packet delivery

    Change-Id: Ibeb815bf2fedfdd644d324c65b58a24871d47d4a

commit c8fd855f32
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 6 10:28:18 2016 -0400

    automatic cleanup of objects upon free/delete

    Change-Id: If244905e2d074f491229316f3305c9b0b1451792

commit 282ef603a8
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jul 6 09:47:29 2016 -0400

    unify read/write functions

    Change-Id: I78b0dd05cd730e16655034994c74cbe23be23fce

commit e74c62cc6f
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Jul 5 15:36:00 2016 -0400

    rename _push to _put and _hold to _get

    Change-Id: I9b0ff5038b541bd3cfb961657c15a26f26ccdfb2

commit d71ce17529
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Jul 5 15:33:07 2016 -0400

    support creation and deletion of streams

    Change-Id: I7df05d232b5971c54ca50adce8144b5f1646fba0

commit 8be4e2c7c4
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Jul 5 11:54:39 2016 -0400

    create functions for redundant code

    Change-Id: Id3772f12294ee9891d22d833274e5935814cae0b

commit 47ce4ca8f5
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Thu Jun 30 12:12:19 2016 -0400

    support creation and deletion of calls objects

    Change-Id: Ie5f9aa978bac21fc30909f14d6a438494848dfd5

commit 8dab54209d
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jun 29 14:20:23 2016 -0400

    create /proc/.../calls directory

    Change-Id: I682a4bf23edbb72772d64963e3ba2cab2a521ff4

commit 1401ae8db5
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jun 29 14:02:11 2016 -0400

    rename kernel message enum

    Change-Id: I45d7aeae43df1fe6ecd6b6965dbd6ba7e7b715d8

commit ce44ff0dbe
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Jun 29 14:00:32 2016 -0400

    convert kernel message data to union

    Change-Id: I7cfd9fe81623efae0a828ba457aa0a4b1380ff03

Change-Id: I4bb0b7f6d29c1c7a2144e4735ed59f3dc0e37094

- The packet counter was accidentally a pointer, resulting in it
  incrementing by 8 instead of 1. That is fixed.
- Use proper formatting macro for uint64_t printing.
- Start PCAP packet indexing at 1 since that is what Wireshark does.

We write out what RTP packet number the SDP came before. When we receive
an SDP offer or answer, we write out the RTP packet number that the SDP
preceeded. This will let us split the RTP recording PCAP around SDP
renegotiation for things like hold/unhold.

Also write out whether the SDP was an offer or an answer.

In the recording metadata files, we now separate each logical section of
metadata by two blank lines. So, it goes:

1. the PCAP file URL
2. two blank lines
3. all answer SDP, each separated by one blank line
4. two blank lines
5. start timestamp
6. end timestamp (no blank line in between)
7. the rest of the file is unstructured metadata (any number of lines)

Added the answer SDP lines to the file format description.

We had initialization code for recording scattered through
"call_interfaces.c", "call.c", and "recording.c". I moved more of the
actual code into functions within recording.c under the parent function
`detect_setup_recording`. We call this function from "call_interfaces.c".
I moved the disjointed bit of PCAP initialization to occur right below
where we toggle recording on or off.

We want to be able to associate call files with a call without the
presence of identifying metadata within the metadata file. To accomplish
this, we prepend the call-id to the start of the pcap recording files
and the call metadata files.

Even though call-id is supposed to be unique, because of paranoia we
keep some of the random affix hex string, but we reduced it down to an
8-byte random value.

Also, some minor argument ordering and name refactoring for random
string generation functions.

Now that all RTP streams for a call go to the same PCAP file, we don't need a
list of multiple PCAP files. We still separate it from the timestamps by an
extra newline.

We should do some more checking to make sure we're using the correct values
for source and destination ip:port pairs.

This involved moving all code from fs.(c|h) to recording.(c|h).
We still spoof packets, so the UDP will look like all monologues are coming
over the same port and will probably look like they are all one stream if
you look at the PCAP file.

We log errors when filesystem operations fail, among other things.

Command line option is "--recording-dir".
Renamed inner recording spool "recordings" to "pcaps".
This is to avoid name sharing conflicts with the "--recording-dir" command
line option, which specifies the recordings spool directory, and the
"$RECORDING_DIR/recordings" inner directory. Changing the inner directory
name to "pcaps" removes this name collision.

In the process, I changed the function names in fs.h to be consistent with
other functions. The names are structure like "$OBJECT_$VERB".

File system code is now in fs.{h|c}. This includes:

    - spool directory setup
    - metadata file management
    - pcap file creation and writing

Random hex string generation is now in str.h.