GA pilot reported near midair collision with unreported traffic on transition through class C airspa...

Narrative:

I was coming back from ZZZ on an oakland transition through class charlie airspace. I was given an instruction to fly from coliseum to the 30 numbers of oak at 2000 feet as instructed. I passed over the coliseum and turned right to 30. Right before the handoff from north tower to south tower - an aircraft came direct head on at my 12 o'clock - passed underneath me way too close. Probably 100-200 feet. Scared the [expletive] out of me. I was never given a traffic advisory or any info about this aircraft; even though I was in the middle of the oak tower airspace pretty much right over the parallel runways. My guess is they were transitioning to the east; probably talking to the south tower - but they didn't give the north tower the memo. Very disconcerting. Ads-B wasn't too helpful there because I was right over the airport and there were a lot of targets (on ground and in air) - so it was hard to make any sense of traffic scope with the targets overlapping. I was about notify tower of the close encounter; but was then given another target at my 12 o'clock; but this time ahead of me and headed in the same direction over the bay. I focused on flying the airplane; and [continued to my destination] safely.

Original NASA ASRS Text

Title: GA pilot reported NMAC with unreported traffic on transition through Class C airspace.

Narrative: I was coming back from ZZZ on an Oakland transition through Class Charlie airspace. I was given an instruction to fly from Coliseum to the 30 numbers of OAK at 2000 feet as instructed. I passed over the coliseum and turned right to 30. Right before the handoff from north tower to south tower - an aircraft came direct head on at my 12 o'clock - passed underneath me way too close. Probably 100-200 feet. Scared the [expletive] out of me. I was never given a traffic advisory or any info about this aircraft; even though I was in the middle of the OAK tower airspace pretty much right over the parallel runways. My guess is they were transitioning to the east; probably talking to the south tower - but they didn't give the north tower the memo. Very disconcerting. ADS-B wasn't too helpful there because I was right over the airport and there were a lot of targets (on ground and in air) - so it was hard to make any sense of traffic scope with the targets overlapping. I was about notify tower of the close encounter; but was then given another target at my 12 o'clock; but this time ahead of me and headed in the same direction over the Bay. I focused on flying the airplane; and [continued to my destination] safely.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1612226
Time
Date	201901
Local Time Of Day	1801-2400
Place
Locale Reference	OAK.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Small Aircraft Low Wing 1 Eng Retractable Gear
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	VFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 91
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Commercial Flight Crew Instrument
Experience	Flight Crew Last 90 Days 3 Flight Crew Total 487 Flight Crew Type 155
Events
Anomaly	ATC Issue All Types Conflict NMAC
Miss Distance	Horizontal 0 Vertical 200

GA pilot reported near midair collision with unreported traffic on transition through class C airspace.