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Improve behaviour of SetReadBuffer / SetWriteBuffer #165

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merged 4 commits into from
May 11, 2020
Merged

Improve behaviour of SetReadBuffer / SetWriteBuffer #165

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64b9c1f
Use SO_RCVBUFFORCE to set read buffer size (see issue #164)
MarkusBauer Mar 24, 2020
74e9b55
Add methods to read back the actual read / send buffer size
MarkusBauer Mar 24, 2020
4e92b43
(fix return value of SetReadBuffer)
MarkusBauer Mar 24, 2020
e4e6787
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May 11, 2020
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70 changes: 66 additions & 4 deletions conn_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ type socket interface {
SetWriteDeadline(t time.Time) error
SetSockoptSockFprog(level, opt int, fprog *unix.SockFprog) error
SetSockoptInt(level, opt, value int) error
GetSockoptInt(level, opt int) (int, error)
}

// dial is the entry point for Dial. dial opens a netlink socket using
Expand Down Expand Up @@ -276,21 +277,67 @@ func (c *conn) SetWriteDeadline(t time.Time) error {
// SetReadBuffer sets the size of the operating system's receive buffer
// associated with the Conn.
func (c *conn) SetReadBuffer(bytes int) error {
return os.NewSyscallError("setsockopt", c.s.SetSockoptInt(
// First try SO_RCVBUFFORCE. Given necessary permissions this syscall ignores limits.
err := os.NewSyscallError("setsockopt", c.s.SetSockoptInt(
unix.SOL_SOCKET,
unix.SO_RCVBUF,
unix.SO_RCVBUFFORCE,
bytes,
))
if err != nil {
// If SO_SNDBUFFORCE fails, try SO_RCVBUF
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Is there a specific syscall error we could inspect to determine if fallback is needed? Would something like os.IsPermission be sufficient?

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The man page does not require a specific error for that case, but the kernel uses EPERM (which is the only logical one of course). Also the permission check is the first thing to happen. I don't think it will ever make a difference if we check for permission errors or not, libnfnetlink does not check for it. Your choice.

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I'm good with leaving it be then, thanks for the info.

err = os.NewSyscallError("setsockopt", c.s.SetSockoptInt(
unix.SOL_SOCKET,
unix.SO_RCVBUF,
bytes,
))
}
return err
}

// SetReadBuffer sets the size of the operating system's transmit buffer
// associated with the Conn.
func (c *conn) SetWriteBuffer(bytes int) error {
return os.NewSyscallError("setsockopt", c.s.SetSockoptInt(
// First try SO_SNDBUFFORCE. Given necessary permissions this syscall ignores limits.
err := os.NewSyscallError("setsockopt", c.s.SetSockoptInt(
unix.SOL_SOCKET,
unix.SO_SNDBUF,
unix.SO_SNDBUFFORCE,
bytes,
))
if err != nil {
// If SO_SNDBUFFORCE fails, try SO_SNDBUF
err = os.NewSyscallError("setsockopt", c.s.SetSockoptInt(
unix.SOL_SOCKET,
unix.SO_SNDBUF,
bytes,
))
}
return err
}

// GetReadBuffer retrieves the size of the operating system's receive buffer
// associated with the Conn.
func (c *conn) GetReadBuffer() (int, error) {
value, err := c.s.GetSockoptInt(
unix.SOL_SOCKET,
unix.SO_RCVBUF,
)
if err != nil {
return 0, os.NewSyscallError("getsockopt", err)
}
return value, nil
}

// GetWriteBuffer retrieves the size of the operating system's transmit buffer
// associated with the Conn.
func (c *conn) GetWriteBuffer() (int, error) {
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value, err := c.s.GetSockoptInt(
unix.SOL_SOCKET,
unix.SO_SNDBUF,
)
if err != nil {
return 0, os.NewSyscallError("getsockopt", err)
}
return value, nil
}

// linuxOption converts a ConnOption to its Linux value.
Expand Down Expand Up @@ -597,6 +644,21 @@ func (s *sysSocket) SetSockoptInt(level, opt, value int) error {
return err
}

func (s *sysSocket) GetSockoptInt(level, opt int) (int, error) {
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var (
value int
err error
)
doErr := s.control(func(fd int) {
value, err = unix.GetsockoptInt(fd, level, opt)
})
if doErr != nil {
return 0, doErr
}

return value, err
}

func (s *sysSocket) SetSockoptSockFprog(level, opt int, fprog *unix.SockFprog) error {
var err error
doErr := s.control(func(fd int) {
Expand Down
14 changes: 12 additions & 2 deletions conn_linux_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -449,12 +449,12 @@ func TestLinuxConnSetBuffers(t *testing.T) {
want := []setSockopt{
{
level: unix.SOL_SOCKET,
opt: unix.SO_RCVBUF,
opt: unix.SO_RCVBUFFORCE,
value: n,
},
{
level: unix.SOL_SOCKET,
opt: unix.SO_SNDBUF,
opt: unix.SO_SNDBUFFORCE,
value: n,
},
}
Expand Down Expand Up @@ -679,6 +679,16 @@ func (s *testSocket) SetSockoptInt(level, opt, value int) error {
return nil
}

func (s *testSocket) GetSockoptInt(level, opt int) (int, error) {
for i := len(s.setSockopt)-1; i >= 0; i-- {
if s.setSockopt[i].level == level && s.setSockopt[i].opt == opt {
return s.setSockopt[i].value, nil
}
}

return 0, errors.New("getsockopt without preceding setsockopt")
}

func (s *testSocket) SetSockoptSockFprog(_, _ int, _ *unix.SockFprog) error {
panic("netlink: testSocket.SetSockoptSockFprog not currently implemented")
}