tcp: frto should not set snd_cwnd to 0
tcp: frto should not set snd_cwnd to 0

Commit 9dc274151a548 (tcp: fix ABC in tcp_slow_start())
uncovered a bug in FRTO code :
tcp_process_frto() is setting snd_cwnd to 0 if the number
of in flight packets is 0.

As Neal pointed out, if no packet is in flight we lost our
chance to disambiguate whether a loss timeout was spurious.

We should assume it was a proper loss.

Reported-by: Pasi Kärkkäinen <87bafea29b0c2826f639529a2dc5da76aef7d636@iki.fi>
Signed-off-by: Neal Cardwell <58d301c70203188c35d379474c26c9cc0636a189@google.com>
Signed-off-by: Eric Dumazet <312c7d941f03386814be517ffdb3e0eb6624e275@google.com>
Cc: Ilpo Järvinen <5801dcaebe162b451612454667e6a167cf0222c1@helsinki.fi>
Cc: Yuchung Cheng <5b5a0a360fa35167ac197fe6359c229fde284cf2@google.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs