robust reentrant buffers

Author: capocasa

lib/pure/nativesockets.nim

@@ -25,6 +25,8 @@ when hostOS == "solaris":
 const useWinVersion = defined(windows) or defined(nimdoc)
 const useNimNetLite = defined(nimNetLite) or defined(freertos) or defined(zephyr) or
     defined(nuttx)
+const smallBufInitSize = when defined(testReentrantBufs): 1 else: 1024
+const largeBufInitSize = when defined(testReentrantBufs): 1 else: 4096
 
 when useWinVersion:
   import std/winlean
@@ -223,13 +225,12 @@ proc getProtoByName*(name: string): int {.since: (1, 3, 5).} =
                           res: ptr ptr posix.Protoent): cint
       {.importc, header: "<netdb.h>".}
     var pe: posix.Protoent
-    var bufSize = 1024
+    var buf = newString(smallBufInitSize)
     while true:
-      var buf = newSeq[char](bufSize)
       let ret = getprotobyname_r(name.cstring, addr pe,
-          cast[cstring](addr buf[0]), csize_t(bufSize), addr protoent)
+          buf.cstring, csize_t(buf.len), addr protoent)
       if ret != ERANGE: break
-      bufSize *= 2
+      buf.setLen(buf.len * 2)
     {.emit: ";\n#else".}
     protoent = posix.getprotobyname(name.cstring)
     {.emit: ";\n#endif".}
@@ -392,13 +393,12 @@ when not useNimNetLite:
     elif defined(linux) and not defined(android):
       var se: posix.Servent
       var s: ptr posix.Servent
-      var bufSize = 1024
+      var buf = newString(smallBufInitSize)
       while true:
-        var buf = newSeq[char](bufSize)
         let ret = getservbyname_r(name.cstring, proto.cstring, addr se,
-            cast[cstring](addr buf[0]), csize_t(bufSize), addr s)
+            buf.cstring, csize_t(buf.len), addr s)
         if ret != ERANGE: break
-        bufSize *= 2
+        buf.setLen(buf.len * 2)
     else:
       var s = posix.getservbyname(name, proto)
     if s == nil: raiseOSError(osLastError(), "Service not found.")
@@ -420,13 +420,12 @@ when not useNimNetLite:
     elif defined(linux) and not defined(android):
       var se: posix.Servent
       var s: ptr posix.Servent
-      var bufSize = 1024
+      var buf = newString(smallBufInitSize)
       while true:
-        var buf = newSeq[char](bufSize)
         let ret = getservbyport_r(uint16(port).cint, proto.cstring, addr se,
-            cast[cstring](addr buf[0]), csize_t(bufSize), addr s)
+            buf.cstring, csize_t(buf.len), addr s)
         if ret != ERANGE: break
-        bufSize *= 2
+        buf.setLen(buf.len * 2)
     else:
       var s = posix.getservbyport(uint16(port).cint, proto)
     if s == nil: raiseOSError(osLastError(), "Service not found.")
@@ -466,21 +465,20 @@ when not useNimNetLite:
       var he: posix.Hostent
       var h_errnop: cint
       var s: ptr posix.Hostent
-      var bufSize = 4096
+      var buf = newString(largeBufInitSize)
       while true:
-        var buf = newSeq[char](bufSize)
         when defined(android4):
           let ret = gethostbyaddr_r(cast[cstring](myAddr), addrLen.SockLen,
                                   cint(family), addr he,
-                                  cast[cstring](addr buf[0]), csize_t(bufSize),
+                                  buf.cstring, csize_t(buf.len),
                                   addr s, addr h_errnop)
         else:
           let ret = gethostbyaddr_r(myAddr, addrLen.SockLen,
                                   cint(family), addr he,
-                                  cast[cstring](addr buf[0]), csize_t(bufSize),
+                                  buf.cstring, csize_t(buf.len),
                                   addr s, addr h_errnop)
         if ret != ERANGE: break
-        bufSize *= 2
+        buf.setLen(buf.len * 2)
       if s == nil:
         raiseOSError(osLastError(), $hstrerror(h_errnop))
     else:
@@ -534,14 +532,13 @@ when not useNimNetLite:
       var he: posix.Hostent
       var h_errnop: cint
       var s: ptr posix.Hostent
-      var bufSize = 4096
+      var buf = newString(largeBufInitSize)
       while true:
-        var buf = newSeq[char](bufSize)
         let ret = gethostbyname_r(name.cstring, addr he,
-            cast[cstring](addr buf[0]), csize_t(bufSize),
+            buf.cstring, csize_t(buf.len),
             addr s, addr h_errnop)
         if ret != ERANGE: break
-        bufSize *= 2
+        buf.setLen(buf.len * 2)
       if s == nil:
         raiseOSError(osLastError(), $hstrerror(h_errnop))
     else:

tests/stdlib/tnativesockets_reentrant.nim

@@ -0,0 +1,35 @@
+discard """
+  matrix: "--mm:refc -d:testReentrantBufs; --mm:orc -d:testReentrantBufs"
+  joinable: false
+"""
+
+## Tests that the _r network calls handle ERANGE buffer resizing correctly.
+## Compiled with -d:testReentrantBufs which sets initial buffers to 1 byte,
+## forcing the while-loop to grow buffers through several ERANGE iterations.
+
+import std/nativesockets
+import std/assertions
+
+when defined(linux):
+  block: # getProtoByName
+    doAssert getProtoByName("tcp") == 6
+    doAssert getProtoByName("udp") == 17
+
+  block: # getServByName
+    let s = getServByName("http", "tcp")
+    doAssert s.name == "http"
+    doAssert s.proto == "tcp"
+
+  block: # getServByPort
+    let s = getServByPort(Port(htons(80)), "tcp")
+    doAssert s.name == "http"
+    doAssert s.proto == "tcp"
+
+  block: # getHostByName
+    let he = getHostByName("localhost")
+    doAssert he.name.len > 0
+    doAssert he.addrList.len > 0
+
+  block: # getHostByAddr
+    let he = getHostByAddr("127.0.0.1")
+    doAssert he.name.len > 0