add (untested) implementation of recvmsg in terms of WSARecvMsg

[catta] / src / compat / windows / wincompat.c

diff --git a/src/compat/windows/wincompat.c b/src/compat/windows/wincompat.c
index 3aa2b2e5d9b00ec7615cc830b32cc2eb6683b65a..d0d239cc7924f10542e8c81a37c785b85c5db86c 100644 (file)
--- a/src/compat/windows/wincompat.c
+++ b/src/compat/windows/wincompat.c
@@ -1,5 +1,113 @@
 #include "wincompat.h"
 #include <errno.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <stdint.h>
+
+// helper: convert WSAGetLastError() to an errno constant
+static int wsa_errno(void)
+{
+    switch(WSAGetLastError()) {
+        case WSAECONNRESET:     return ECONNRESET;
+        case WSAEFAULT:         return EFAULT;
+        case WSAEINPROGRESS:    return EINPROGRESS;
+        case WSAEINTR:          return EINTR;
+        case WSAEINVAL:         return EINVAL;
+        case WSAEMSGSIZE:       return EMSGSIZE;
+        case WSAENETDOWN:       return ENETDOWN;
+        case WSAENETRESET:      return ENETRESET;
+        case WSAENOTCONN:       return ENOTCONN;
+        case WSAENOTSOCK:       return ENOTSOCK;
+        case WSAEOPNOTSUPP:     return EOPNOTSUPP;
+        case WSAEWOULDBLOCK:    return EWOULDBLOCK;
+        default:
+            return EINVAL;
+    }
+}
+
+ssize_t recvmsg(int sockfd, struct msghdr *msg, int flags)
+{
+    LPFN_WSARECVMSG WSARecvMsg = NULL;
+    GUID wsaid = WSAID_WSARECVMSG;
+    DWORD b;
+
+    DWORD bytesrcvd;
+    WSAMSG wsamsg;
+    size_t i;
+    int r;
+
+    // size_t is larger than DWORD on 64bit
+    if(msg->msg_iovlen > UINT32_MAX) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    // obtain the function pointer to WSARecvMsg
+    r = WSAIoctl(sockfd, SIO_GET_EXTENSION_FUNCTION_POINTER,
+                 &wsaid, sizeof(wsaid), &WSARecvMsg, sizeof(WSARecvMsg),
+                 &b, NULL, NULL);
+    if(r == SOCKET_ERROR) {
+        errno = wsa_errno();
+        return -1;
+    }
+    assert(b == sizeof(WSARecvMsg));
+    assert(WSARecvMsg != NULL);
+
+    // convert msghdr to WSAMSG structure
+    wsamsg.name = msg->msg_name;
+    wsamsg.namelen = msg->msg_namelen;
+    wsamsg.lpBuffers = malloc(msg->msg_iovlen * sizeof(WSABUF));
+    wsamsg.dwBufferCount = msg->msg_iovlen;
+    wsamsg.Control.len = msg->msg_controllen;
+    wsamsg.Control.buf = msg->msg_control;
+    wsamsg.dwFlags = (DWORD)flags;
+
+    // all flags that fit into dwFlags also fit through the flags argument
+    assert(sizeof(DWORD) <= sizeof(flags));
+
+    if(wsamsg.lpBuffers == NULL) {
+        // malloc will have set errno
+        return -1;
+    }
+
+    // re-wrap iovecs as WSABUFs
+    for(i=0; i<msg->msg_iovlen; i++) {
+        // size_t vs. u_long
+        if(msg->msg_iov[i].iov_len > ULONG_MAX) {
+            free(wsamsg.lpBuffers);
+            errno = EINVAL;
+            return -1;
+        }
+
+        wsamsg.lpBuffers[i].len = msg->msg_iov[i].iov_len;
+        wsamsg.lpBuffers[i].buf = msg->msg_iov[i].iov_base;
+    }
+
+    r = WSARecvMsg(sockfd, &wsamsg, &bytesrcvd, NULL, NULL);
+
+    // the allocated WSABUF wrappers are no longer needed
+    free(wsamsg.lpBuffers);
+
+    if(r == SOCKET_ERROR) {
+        // XXX do we need special handling for ENETRESET, EMSGSIZE, ETIMEDOUT?
+        errno = wsa_errno();
+        return -1;
+    }
+
+    // DWORD has one bit more than ssize_t on 32bit
+    if(bytesrcvd > SSIZE_MAX) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    // transfer results from wsamsg to msg
+    // NB: the data and control buffers are shared
+    msg->msg_controllen = wsamsg.Control.len;
+    msg->msg_flags = (int)wsamsg.dwFlags;
+        // all flags that fit into dwFlags also fit into msg_flags (see above)
+
+    return bytesrcvd;
+}
 
 int uname(struct utsname *buf)
 {