Add UMA histogram for Expect-CT header processing

Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignored because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871
Committed: https://crrev.com/d7ef7ecd31c1a7a6cbbe054445e96ca5130a0f1d
Cr-Commit-Position: refs/heads/master@{#414940}

[estark, 2016-08-25 23:27:22]

The CQ bit was checked by estark@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-25 23:27:59]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[estark, 2016-08-25 23:28:54]

estark@chromium.org changed reviewers:
+ eroman@chromium.org, jwd@chromium.org

[estark, 2016-08-25 23:28:55]

eroman, can you please review //net?
jwd, can you please review histograms.xml?

[estark, 2016-08-25 23:29:08]

estark@chromium.org changed reviewers:
+ eranm@chromium.org

[estark, 2016-08-25 23:29:08]

+eranm as well

[eroman, 2016-08-25 23:34:03]

nit in CL description " or it might be ignore because"  --> " or it might be
ignored because"

[estark, 2016-08-25 23:36:11]

Description was changed from

==========
Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignore because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871
==========

to

==========
Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignored because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871
==========

[estark, 2016-08-25 23:36:21]

On 2016/08/25 23:34:03, eroman wrote:
> nit in CL description " or it might be ignore because"  --> " or it might be
> ignored because"

Thanks, fixed.

[eroman, 2016-08-25 23:39:31]

lgtm

https://codereview.chromium.org/2272323004/diff/1/net/http/transport_security...
File net/http/transport_security_state.cc (right):

https://codereview.chromium.org/2272323004/diff/1/net/http/transport_security...
net/http/transport_security_state.cc:1298: // histogrammed, so do not reorder or
remove values.
Given this, can you assign values to *each* of the enums not just the first?

https://codereview.chromium.org/2272323004/diff/1/net/http/transport_security...
net/http/transport_security_state.cc:1319: EXPECT_CT_HEADER_MAX
I think it is more idiomatic to use a _LAST value and set it to the exact value
of last element (to prevent needing to handle this sentinel value inside of
switch statements).

Given this is only used locally in the function though, I guess it doesn't
really matter.

[commit-bot: I haz the power, 2016-08-26 01:50:52]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-26 01:50:52]

Dry run: This issue passed the CQ dry run.

[jwd, 2016-08-26 20:20:18]

LGTM with eroman@'s comments

[estark, 2016-08-27 15:20:05]

Thanks, both!

https://codereview.chromium.org/2272323004/diff/1/net/http/transport_security...
File net/http/transport_security_state.cc (right):

https://codereview.chromium.org/2272323004/diff/1/net/http/transport_security...
net/http/transport_security_state.cc:1298: // histogrammed, so do not reorder or
remove values.
On 2016/08/25 23:39:31, eroman wrote:
> Given this, can you assign values to *each* of the enums not just the first?

Done.

https://codereview.chromium.org/2272323004/diff/1/net/http/transport_security...
net/http/transport_security_state.cc:1319: EXPECT_CT_HEADER_MAX
On 2016/08/25 23:39:31, eroman wrote:
> I think it is more idiomatic to use a _LAST value and set it to the exact
value
> of last element (to prevent needing to handle this sentinel value inside of
> switch statements).
> 
> Given this is only used locally in the function though, I guess it doesn't
> really matter.

Done.

[estark, 2016-08-27 15:20:11]

The CQ bit was checked by estark@chromium.org

[estark, 2016-08-27 15:20:12]

The patchset sent to the CQ was uploaded after l-g-t-m from eroman@chromium.org,
jwd@chromium.org
Link to the patchset: https://codereview.chromium.org/2272323004/#ps20001
(title: "eroman comments")

[commit-bot: I haz the power, 2016-08-27 15:20:17]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-27 16:43:27]

Description was changed from

==========
Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignored because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871
==========

to

==========
Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignored because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871
==========

[commit-bot: I haz the power, 2016-08-27 16:43:28]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-08-27 16:45:07]

Description was changed from

==========
Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignored because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871
==========

to

==========
Add UMA histogram for Expect-CT header processing

This CL adds a histogram to record the result of processing an Expect-CT
header. (An Expect-CT header tells Chrome that the site wants to receive
reports whenever a connection does not comply with Chrome CT policy.)

For example, a header might be received but thrown out because the site
was not on the preload list, or it might be ignored because the site
complied with the CT policy. This histogram will help us sanity-check
server-side metrics. (In particular, we aren't receiving any reports --
we'd like to sanity check that that is because Chrome users are always
getting CT-compliant connections, and not because there is a bug in
report-sending or Expect-CT header-serving.) This will also give us an
easy way to estimate worst-case traffic on the report collection server
(if we know how many users are seeing Expect-CT headers, we can estimate
the number of reports that would be sent if a large-scale
misconfiguration made an Expect-CT site non-compliant.)

BUG=638871

Committed: https://crrev.com/d7ef7ecd31c1a7a6cbbe054445e96ca5130a0f1d
Cr-Commit-Position: refs/heads/master@{#414940}
==========

[commit-bot: I haz the power, 2016-08-27 16:45:08]

Patchset 2 (id:??) landed as
https://crrev.com/d7ef7ecd31c1a7a6cbbe054445e96ca5130a0f1d
Cr-Commit-Position: refs/heads/master@{#414940}