code review 6852085: net: never return -1 bytes read from netFD.Read

net: never return -1 bytes read from netFD.Read

If the a network read would block, and a packet arrived just before the timeout expired, then the number of bytes from the previous (blocking) read, -1, would be returned.

This change restores the previous logic, where n would be unconditionally set to 0 if err != nil, but was skipped due to a change in CL 6851096.

The test for this change is CL 6851061.

[dave_cheney.net, 2012-11-25 11:43:18]

Hello bradfitz@golang.org, mikioh.mikioh@gmail.com, dvyukov@google.com (cc:
golang-dev@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go

[rsc, 2012-11-25 16:18:11]

LGTM

[bradfitz, 2012-11-25 17:19:17]

LGTM

nice, thanks!


On Sun, Nov 25, 2012 at 3:43 AM, <dave@cheney.net> wrote:

> Reviewers: bradfitz, mikio, dvyukov,
>
> Message:
> Hello bradfitz@golang.org, mikioh.mikioh@gmail.com, dvyukov@google.com
> (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change to
> https://code.google.com/p/go
>
>
> Description:
> net: never return -1 bytes read from netFD.Read
>
> If the a network read would block, and a packet arrived just before the
> timeout expired, then the number of bytes from the previous (blocking)
> read, -1, would be returned.
>
> This change restores the previous logic, where n would be
> unconditionally set to 0 if err != nil, but was skipped due to a change
> in CL 6851096.
>
> The test for this change is CL 6851061.
>
> Please review this at
http://codereview.appspot.com/**6852085/<http://codereview.appspot.com/6852085/>
>
> Affected files:
>   M src/pkg/net/fd_unix.go
>
>
> Index: src/pkg/net/fd_unix.go
> ==============================**==============================**=======
> --- a/src/pkg/net/fd_unix.go
> +++ b/src/pkg/net/fd_unix.go
> @@ -431,6 +431,7 @@
>                 }
>                 n, err = syscall.Read(int(fd.sysfd), p)
>                 if err == syscall.EAGAIN {
> +                       n = 0
>                         err = errTimeout
>                         if fd.rdeadline >= 0 {
>                                 if err = fd.pollServer.WaitRead(fd); err
> == nil {
> @@ -467,6 +468,7 @@
>                 }
>                 n, sa, err = syscall.Recvfrom(fd.sysfd, p, 0)
>                 if err == syscall.EAGAIN {
> +                       n = 0
>                         err = errTimeout
>                         if fd.rdeadline >= 0 {
>                                 if err = fd.pollServer.WaitRead(fd); err
> == nil {
> @@ -501,6 +503,7 @@
>                 }
>                 n, oobn, flags, sa, err = syscall.Recvmsg(fd.sysfd, p,
> oob, 0)
>                 if err == syscall.EAGAIN {
> +                       n = 0
>                         err = errTimeout
>                         if fd.rdeadline >= 0 {
>                                 if err = fd.pollServer.WaitRead(fd); err
> == nil {
>
>
>

[dave_cheney.net, 2012-11-25 23:59:51]

*** Submitted as http://code.google.com/p/go/source/detail?r=03a6b8c9c396 ***

net: never return -1 bytes read from netFD.Read

If the a network read would block, and a packet arrived just before the timeout
expired, then the number of bytes from the previous (blocking) read, -1, would
be returned.

This change restores the previous logic, where n would be unconditionally set to
0 if err != nil, but was skipped due to a change in CL 6851096.

The test for this change is CL 6851061.

R=bradfitz, mikioh.mikioh, dvyukov, rsc
CC=golang-dev
http://codereview.appspot.com/6852085