Android USB tethering相关代码

1. 代码位置

packages/apps/Settings/src/com/android/settings/TetherSettings.java
frameworks/base/services/java/com/android/server/connectivity/Tethering.java
frameworks/base/core/java/android/net/ConnectivityManager.java
frameworks/base/services/core/java/com/android/server/ConnectivityService.java
frameworks/base/services/java/com/android/server/NetworkManagementService.java
system/netd/CommandListener.cpp,TetherController.cpp,NatController.cpp

2. 调用流程
packages/apps/Settings/src/com/android/settings/TetherSettings.java
private void setUsbTethering(boolean enabled) {
ConnectivityManager cm =
(ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
mUsbTether.setChecked(false);
if (cm.setUsbTethering(enabled) != ConnectivityManager.TETHER_ERROR_NO_ERROR) {
mUsbTether.setSummary(R.string.usb_tethering_errored_subtext);
return;
}
mUsbTether.setSummary("");
}
调用关系
setUsbTethering(true);
cm.setUsbTethering(enabled)
mService.setUsbTethering(enable); frameworks/base/core/java/android/net/ConnectivityManager.java
mTethering.setUsbTethering(enable); frameworks/base/services/core/java/com/android/server/ConnectivityService.java

frameworks/base/services/core/java/com/android/server/connectivity/Tethering.java
setUsbTethering()
mUsbTetherRequested = true;
usbManager.setCurrentFunction(UsbManager.USB_FUNCTION_RNDIS, false);

onReceive()
if (action.equals(UsbManager.ACTION_USB_STATE)) {
if (usbConnected && mRndisEnabled && mUsbTetherRequested)
tetherUsb(true);
tether(iface) "Tethering rndis0"
sm.sendMessage(TetherInterfaceSM.CMD_TETHER_REQUESTED)
TetherInterfaceSM(InitialState): CMD_TETHER_REQUESTED (2)
sendMessage(TetherMasterSM.CMD_TETHER_MODE_REQUESTED 1)
transitionTo(mStartingState);
TetherInterfaceSM(mStartingState)
Tethering.this.configureUsbIface
ifcg.setInterfaceUp();
mNMService.setInterfaceConfig(iface, ifcg); INetworkManagementService:networkManagerService.java
CommandListener::setcfg() "CommandListener: Setting iface cfg" "CommandListener: Trying to bring up rndis0"
sendTetherStateChangedBroadcast();
"Tethering: sendTetherStateChangedBroadcast 0, 1, 0"
transitionTo(mTetheredState);
TetherInterfaceSM(mTetheredState)
mNMService.tetherInterface(mIfaceName);
tetherInterface() networkManagerService.java
CommandListener: TetherCmd::runCommand. argc: 4. argv[0]: tether
TetherController::tetherInterface() TetherController.cpp
addV6RtrAdvIface()
applyDnsInterfaces()
"Tethering: Tethered rndis0"

TetherMasterSM(InitialState): CMD_TETHER_MODE_REQUESTED(1)
transitionTo(mTetherModeAliveState);
TetherMasterSM(TetherModeAliveState)
turnOnMasterTetherSettings();
mNMService.setIpForwardingEnabled(true);
setIpFwdEnabled() TetherController.cpp
echo 1 > /proc/sys/net/ipv4/ip_forward
echo 2 > /proc/sys/net/ipv6/conf/all/proxy_ndp
echo 2 > /proc/sys/net/ipv6/conf/all/forwarding
mNMService.startTethering(mDhcpRange);
TetherCmd::runCommand. argc: 18. argv[0]: tether CommandListener.cpp
TetherController::startTethering "Starting tethering services"
exec("/system/bin/dnsmasq")
"dnsmasq : started, version 2.51 cachesize 150"
mNMService.setDnsForwarders(mDefaultDnsServers);
TetherController:setDnsForwarders "Sending update msg to dnsmasq"
update_dns:8.8.8.8:8.8.4.4
update_dns:123.123.123.123:123.123.123.124
chooseUpstreamType(mTryCell);
"chooseUpstreamType(true), preferredApn =5, got type=0"
notifyTetheredOfNewUpstreamIface
"notifying tethered with iface =rmnet0"
sendMessage(TetherInterfaceSM.CMD_TETHER_CONNECTION_CHANGED)
TetherInterfaceSM(TetheredState) CMD_TETHER_CONNECTION_CHANGED
mNMService.enableNat(mIfaceName, newUpstreamIfaceName);
"Enabling NAT - Tethered Iface = rndis0 newUpstreamIfaceName =rmnet0"
NatController: enableNat(intIface=<rndis0>, extIface=<rmnet0>)
/system/bin/iptables -t nat -A natctrl_nat_POSTROUTING -o rmnet0 -j MASQUERADE
/system/bin/iptables -A natctrl_FORWARD -i rmnet0 -o rndis0 -m state --state ESTABLISHED,RELATED -g natctrl_tether_counters
/system/bin/iptables -A natctrl_FORWARD -i rndis0 -o rmnet0 -m state --state INVALID -j DROP
/system/bin/iptables -A natctrl_FORWARD -i rndis0 -o rmnet0 -g natctrl_tether_counters
/system/bin/iptables -A natctrl_tether_counters -i rndis0 -o rmnet0 -j RETURN
/system/bin/iptables -A natctrl_tether_counters -i rmnet0 -o rndis0 -j RETURN
/system/bin/iptables -D natctrl_FORWARD -j DROP
/system/bin/iptables -A natctrl_FORWARD -j DROP

system/netd/CommandListener.cpp
setcfg
ifc_up() system/core/libnetutils/ifc_utils.c
ifc_set_flags(name, IFF_UP, 0);
ioctl(ifc_ctl_sock, SIOCSIFFLAGS, &ifr)

3.dnsmasq正常log

D CommandListener: TetherCmd::runCommand. argc: 16. argv[0]: tether
D TetherController: Starting tethering services
D TetherController: Sending update msg to dnsmasq [update_ifaces:rndis0]
D TetherController: Sending update msg to dnsmasq [update_dns:8.8.8.8:8.8.4.4]
I dnsmasq : started, version 2.51 cachesize 150
I dnsmasq : compile time options: no-IPv6 GNU-getopt no-DBus no-I18N DHCP no-scripts no-TFTP
W dnsmasq : warning: no upstream servers configured
I dnsmasq : DHCP, IP range 192.168.48.2 -- 192.168.48.254, lease time 1h
I dnsmasq : DHCP, IP range 192.168.47.2 -- 192.168.47.254, lease time 1h
I dnsmasq : DHCP, IP range 192.168.46.2 -- 192.168.46.254, lease time 1h
I dnsmasq : DHCP, IP range 192.168.45.2 -- 192.168.45.254, lease time 1h
I dnsmasq : DHCP, IP range 192.168.44.2 -- 192.168.44.254, lease time 1h
I dnsmasq : DHCP, IP range 192.168.43.2 -- 192.168.43.254, lease time 1h
I dnsmasq : DHCP, IP range 192.168.42.2 -- 192.168.42.254, lease time 1h
I dnsmasq : read /etc/hosts - 1 addresses
I dnsmasq : using nameserver 8.8.4.4#53
I dnsmasq : using nameserver 8.8.8.8#53
D TetherController: Sending update msg to dnsmasq [update_dns:221.130.33.52:221.130.33.60]
I dnsmasq : using nameserver 221.130.33.60#53
I dnsmasq : using nameserver 221.130.33.52#53
I dnsmasq : DHCPREQUEST(rndis0) 192.168.42.5 02:19:03:66:78:76
I dnsmasq : DHCPACK(rndis0) 192.168.42.5 02:19:03:66:78:76 pcname
W dnsmasq : Ignoring domain corpusers.net for DHCP host name pcname
I dnsmasq : DHCPREQUEST(rndis0) 192.168.42.5 02:19:03:66:78:76
I dnsmasq : DHCPACK(rndis0) 192.168.42.5 02:19:03:66:78:76 pcname
W dnsmasq : Ignoring domain corpusers.net for DHCP host name pcname
I dnsmasq : DHCPINFORM(rndis0) 192.168.42.5 02:19:03:66:78:76
I dnsmasq : DHCPACK(rndis0) 192.168.42.5 02:19:03:66:78:76 pcname

4. Debug方法

4.1. 手机端运行ip r l/netcfg检查rmnet0, rndis0是否up；如rndis0没有up,检查ifc_up()函数及usb kernel part
4.2. PC端运行ipconfig检查是否从手机分配到ip address（关闭PC端的其他网络，如局域网/WLAN）;如没有检查进程dnsmasq是否启动

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