unix: add tcp_md5sig on Linux

This structure is used with setsockopt in BGP speaker implementations.

For more information, please see:
https://criticalindirection.com/2015/05/12/tcp_md5sig/.

Fixes golang/go#24830

Change-Id: Ic2137e843ad502dbe9a4227362b63164789c5877
Reviewed-on: https://go-review.googlesource.com/106656
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/unix/ztypes_linux_mipsle.go b/unix/ztypes_linux_mipsle.go
index 67ac81e..b9e57eb 100644
--- a/unix/ztypes_linux_mipsle.go
+++ b/unix/ztypes_linux_mipsle.go
@@ -1127,3 +1127,18 @@
 	CBitFieldMaskBit62 = 0x4000000000000000
 	CBitFieldMaskBit63 = 0x8000000000000000
 )
+
+type SockaddrStorage struct {
+	Family uint16
+	_      [122]int8
+	_      uint32
+}
+
+type TCPMD5Sig struct {
+	Addr      SockaddrStorage
+	Flags     uint8
+	Prefixlen uint8
+	Keylen    uint16
+	_         uint32
+	Key       [80]uint8
+}