swrap: Add swrap_msghdr_add_cmsghdr().

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>
Pair-Programmed-With: Michael Adam <obnox@samba.org>
Signed-off-by: Andreas Schneider <asn@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Michael Adam <obnox@samba.org>

diff --git a/lib/socket_wrapper/socket_wrapper.c b/lib/socket_wrapper/socket_wrapper.c
index e1b69fa94b1d2cb6e83819432ad70890d8aed090..d3824597810fcafda7bf8e3dccb2e5521cf91020 100644 (file)
--- a/lib/socket_wrapper/socket_wrapper.c
+++ b/lib/socket_wrapper/socket_wrapper.c
@@ -2964,6 +2964,77 @@ int ioctl(int s, unsigned long int r, ...)
        return rc;
 }
 
+/*****************
+ * CMSG
+ *****************/
+
+#ifdef HAVE_STRUCT_MSGHDR_MSG_CONTROL
+/**
+ * @brief Add a cmsghdr to a msghdr.
+ *
+ * This is an function to add any type of cmsghdr. It will operate on the
+ * msg->msg_control and msg->msg_controllen you pass in by adapting them to
+ * the buffer position after the added cmsg element. Hence, this function is
+ * intended to be used with an intermediate msghdr and not on the original
+ * one handed in by the client.
+ *
+ * @param[in]  msg      The msghdr to which to add the cmsg.
+ *
+ * @param[in]  level    The cmsg level to set.
+ *
+ * @param[in]  type     The cmsg type to set.
+ *
+ * @param[in]  data     The cmsg data to set.
+ *
+ * @param[in]  len      the length of the data to set.
+ */
+static void swrap_msghdr_add_cmsghdr(struct msghdr *msg,
+                                    int level,
+                                    int type,
+                                    const void *data,
+                                    size_t len)
+{
+       size_t cmlen = CMSG_LEN(len);
+       size_t cmspace = CMSG_SPACE(len);
+       uint8_t cmbuf[cmspace];
+       struct cmsghdr *cm = (struct cmsghdr *)cmbuf;
+       uint8_t *p;
+
+       memset(cmbuf, 0, cmspace);
+
+       if (msg->msg_controllen < cmlen) {
+               cmlen = msg->msg_controllen;
+               msg->msg_flags |= MSG_CTRUNC;
+       }
+
+       if (msg->msg_controllen < cmspace) {
+               cmspace = msg->msg_controllen;
+       }
+
+       /*
+        * We copy the full input data into an intermediate cmsghdr first
+        * in order to more easily cope with truncation.
+        */
+       cm->cmsg_len = cmlen;
+       cm->cmsg_level = level;
+       cm->cmsg_type = type;
+       memcpy(CMSG_DATA(cm), data, len);
+
+       /*
+        * We now copy the possibly truncated buffer.
+        * We copy cmlen bytes, but consume cmspace bytes,
+        * leaving the possible padding uninitialiazed.
+        */
+       p = (uint8_t *)msg->msg_control;
+       memcpy(p, cm, cmlen);
+       p += cmspace;
+       msg->msg_control = p;
+       msg->msg_controllen -= cmspace;
+
+       return;
+}
+#endif /* HAVE_STRUCT_MSGHDR_MSG_CONTROL */
+
 static ssize_t swrap_sendmsg_before(int fd,
                                    struct socket_info *si,
                                    struct msghdr *msg,