If we want to write a service in the Android framework, how can we do ?
There are some things we should know before starting to implement.
– what is UID in Android ? what’s different with Linux UID ?
– what is the relationship between UID and PID ?
– how can we use libpcap for Applications in the embedded system ?
This article will answer those questions and point out a direction.
Overview:
Android framework | Linux space | Network stack |
An UID for an app <—–> maybe PIDs <—> Socket IP & Port
- What is UID in Android ? what’s different with Linux UID ?
UID := user ID (UID) is particular to each Android application.
Each Android package (.apk) installed will be given an unique Linux user ID, creating a kernel-level Application Sandbox.
Ref. https://stackoverflow.com/questions/5708906/what-is-uid-on-android - How can we get UID ?
– If you implement App or Framework service, using:PackageManagerandgetApplicationInfo().
– If you want to use adb for testing purpose, using
adb shell dumpsys package {package name} | grep userId=
e.g. adb shell dumpsys package com.android.phone | grep userId=
It will show an number larger than 10000. (UID >= 10000)
Ref. https://blog.csdn.net/zhao007z5/article/details/79973752
- What is the relationship between UID and PID ?
UID is user ID.
PID is process ID.
One UID may have multiple PIDs.
Get PID:
adb shell pidof -s {package name}
More information:
adb shell cat /proc/{pid}/status - How can we use libpcap for Applications in the embedded system ?
If you want to use tcpdump,
– find the local address of socket,netstat -tuporss -tup
–tcpdump -i wlan0 src <IP> and port <PORT>
If you want to use Iptables,
– find PIDs of APP.
– iptables -I OUTPUT -m owner –uid-owner -j LOG –log-level 7 –log-prefix ‘SNIFFER: ‘ –log-uid
If you want to use netstat,
– netstat -np –inet | grep “package name”
Ref.
netstat: https://unix.stackexchange.com/questions/375387/how-to-trace-networking-activity-of-a-command
How to view network traffic requested by a specific app?
