Improve SendMsg performance.

SendMsg before this change would copy all the data over into a
new slice even if the underlying socket could only accept a
small amount of data. This is really inefficient with non-blocking
sockets and under high throughput where large writes could get
ErrWouldBlock or if there was say a timeout associated with the sendmsg()
syscall.

With this change we delay copying bytes in till they are needed and only
copy what can be potentially sent/held in the socket buffer. Reducing
the need to repeatedly copy data over.

Also a minor fix to change state FIN-WAIT-1 when shutdown(..., SHUT_WR) is called
instead of when we transmit the actual FIN. Otherwise the socket could remain in
CONNECTED state even though the user has called shutdown() on the socket.

Updates #627

PiperOrigin-RevId: 263430505

0 files changed, 0 insertions, 0 deletions