The channels {cancel,resCh} have roughly the same lifetime and are used for
roughly the same purpose as an entry's waiters; we can unify the state
management of the two mechanisms, while also reducing unncessary mutex locking
and unlocking.
Made some cosmetic changes while I'm here.
PiperOrigin-RevId: 218343915
Change-Id: Ic69546a2b7b390162b2231f07f335dd6199472d7
Previously, if address resolution for UDP or Ping sockets required sending
packets using Write in Transport layer, Resolve would return ErrWouldBlock
and Write would return ErrNoLinkAddress. Meanwhile startAddressResolution
would run in background. Further calls to Write using same address would also
return ErrNoLinkAddress until resolution has been completed successfully.
Since Write is not allowed to block and System Calls need to be
interruptible in System Call layer, the caller to Write is responsible for
blocking upon return of ErrWouldBlock.
Now, when startAddressResolution is called a notification channel for
the completion of the address resolution is returned.
The channel will traverse up to the calling function of Write as well as
ErrNoLinkAddress. Once address resolution is complete (success or not) the
channel is closed. The caller would call Write again to send packets and
check if address resolution was compeleted successfully or not.
Fixesgoogle/gvisor#5
Change-Id: Idafaf31982bee1915ca084da39ae7bd468cebd93
PiperOrigin-RevId: 214962200
Tamir Duberstein
Ian Gudger
Sepehr Raissian
Zhaozhong Ni
Nicolas Lacasse
Googler