[PATCH 3/3] socket: prevent recvfrom from returning garbage

[Alexander Turenko]

On Fri, Aug 24, 2018 at 04:07:48PM +0300, Vladimir Davydov wrote:
> On Fri, Aug 24, 2018 at 05:47:39AM +0300, Alexander Turenko wrote:
> > In C recvfrom function sets addrlen parameter to zero when called on TCP
> > socket (at least on Linux). The src_addr parameter can contain garbage
> > in the case, so we should not dereference it.
> > 
> > Before this commit socket:recvfrom() can return 'from' table with only
> > family field (don't sure why, but addr->sa_family often contain PF_INET
> > value in my case) or return nil depending on the garbage at the address.
> > Now it always return nil.
> > ---
> >  src/lua/socket.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> 
> Could you please add a test case?

Added in the previous commit ('case: recvfrom truncate the message with
tcp'). The main purpose of the test case is another, but when added I
found the flakiness ('from' could be {family = 'AF_INET'} or nil from
time to time) and fixed it here.

How to better handle this? I suppose I should add a comment to the test
case that it also test this case?

WBR, Alexander Turenko.