diff --git a/CHANGES b/CHANGES
index aa9dcb1..ee7f55b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -21,6 +21,12 @@ Corrections:
 	Mitigated race condition of quickly terminating SYSTEM or EXEC child
 	processes.
 
+	Option o-direct might require alignment of read/write buffer to, e.g.,
+	512 bytes, Socat now takes care of this when allocating the buffer.
+	With this fix read() succeeds, however, write() still might fail when
+	not writing complete pages.
+	Test: O_DIRECT
+
 Porting:
 	In gcc version 10 the default changed from -fcommon to -fno-common.
 	Consequently, linking filan and procan failed with error
diff --git a/config.h.in b/config.h.in
index 57de248..ecb8112 100644
--- a/config.h.in
+++ b/config.h.in
@@ -69,6 +69,9 @@
 /* Define if you have the socket function.  */
 #undef HAVE_SOCKET
 
+/* Define if you have the posix_memalign function.  */
+#undef HAVE_PROTOTYPE_LIB_posix_memalign
+
 /* Define if you have the strdup function.  */
 #undef HAVE_PROTOTYPE_LIB_strdup
 
diff --git a/configure.ac b/configure.ac
index f39081b..3d04cbb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -785,6 +785,7 @@ AC_CHECK_FUNCS(cfsetispeed cfgetispeed cfsetospeed cfgetospeed)
 ###################################
 # check for prototype and existence of functions that return a pointer
 # defines in config.h: HAVE_PROTOTYPE_LIB_$1
+AC_CHECK_PROTOTYPE_LIB(posix_memalign)
 AC_CHECK_PROTOTYPE_LIB(strdup)
 AC_CHECK_PROTOTYPE_LIB(strerror)
 AC_CHECK_PROTOTYPE_LIB(strstr)
@@ -794,7 +795,6 @@ AC_CHECK_PROTOTYPE_LIB(memrchr)
 AC_CHECK_PROTOTYPE_LIB(if_indextoname)
 AC_CHECK_PROTOTYPE_LIB(ptsname)
 
-
 AC_MSG_CHECKING(for long long)
 AC_CACHE_VAL(sc_cv_type_longlong,
 [AC_TRY_COMPILE([],[long long s;],
diff --git a/socat.c b/socat.c
index f6fe0fc..3e94c78 100644
--- a/socat.c
+++ b/socat.c
@@ -57,7 +57,7 @@ void socat_opt_hint(FILE *fd, char a, char b);
 void socat_version(FILE *fd);
 int socat(const char *address1, const char *address2);
 int _socat(void);
-int cv_newline(unsigned char **buff, ssize_t *bytes, int lineterm1, int lineterm2);
+int cv_newline(unsigned char *buff, ssize_t *bytes, int lineterm1, int lineterm2);
 void socat_signal(int sig);
 static int socat_sigchild(struct single *file);
 
@@ -708,7 +708,7 @@ int childleftdata(xiofile_t *xfd) {
 }
 
 int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
-		unsigned char **buff, size_t bufsiz, bool righttoleft);
+		unsigned char *buff, size_t bufsiz, bool righttoleft);
 
 bool mayrd1;		/* sock1 has read data or eof, according to poll() */
 bool mayrd2;		/* sock2 has read data or eof, according to poll() */
@@ -765,8 +765,21 @@ int _socat(void) {
       Error2("buffer size option (-b) to big - "F_Zu" (max is "F_Zu")", socat_opts.bufsiz, (SIZE_MAX-1)/2);
       socat_opts.bufsiz = (SIZE_MAX-1)/2;
    }
+
+#if HAVE_PROTOTYPE_LIB_posix_memalign
+   /* Operations on files with flag O_DIRECT might need buffer alignment.
+      Without this, eg.read() fails with "Invalid argument" */
+   {
+      int _errno;
+      if ((_errno = Posix_memalign((void **)&buff, getpagesize(), 2*socat_opts.bufsiz+1)) != 0) {
+	 Error1("posix_memalign(): %s", strerror(_errno));
+	 return -1;
+      }
+   }
+#else /* !HAVE_PROTOTYPE_LIB_posix_memalign */
    buff = Malloc(2*socat_opts.bufsiz+1);
    if (buff == NULL)  return -1;
+#endif /* !HAVE_PROTOTYPE_LIB_posix_memalign */
 
    if (socat_opts.logopt == 'm' && xioinqopt('l', NULL, 0) == 'm') {
       Info("switching to syslog");
@@ -988,7 +1001,7 @@ int _socat(void) {
 
       if (mayrd1 && maywr2) {
 	 mayrd1 = false;
-	 if ((bytes1 = xiotransfer(sock1, sock2, &buff, socat_opts.bufsiz, false))
+	 if ((bytes1 = xiotransfer(sock1, sock2, buff, socat_opts.bufsiz, false))
 	     < 0) {
 	    if (errno != EAGAIN) {
 	       closing = MAX(closing, 1);
@@ -1020,7 +1033,7 @@ int _socat(void) {
 
       if (mayrd2 && maywr1) {
 	 mayrd2 = false;
-	 if ((bytes2 = xiotransfer(sock2, sock1, &buff, socat_opts.bufsiz, true))
+	 if ((bytes2 = xiotransfer(sock2, sock1, buff, socat_opts.bufsiz, true))
 	     < 0) {
 	    if (errno != EAGAIN) {
 	       closing = MAX(closing, 1);
@@ -1106,7 +1119,7 @@ int _socat(void) {
    xioclose(sock1);
    xioclose(sock2);
 
-		  free(buff);
+   free(buff);
    return 0;
 }
 
@@ -1194,10 +1207,10 @@ static int
    */
 /* inpipe, outpipe must be single descriptors (not dual!) */
 int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
-		unsigned char **buff, size_t bufsiz, bool righttoleft) {
+		unsigned char *buff, size_t bufsiz, bool righttoleft) {
    ssize_t bytes, writt = 0;
 
-	 bytes = xioread(inpipe, *buff, bufsiz);
+	 bytes = xioread(inpipe, buff, bufsiz);
 	 if (bytes < 0) {
 	    if (errno != EAGAIN)
 	       XIO_RDSTREAM(inpipe)->eof = 2;
@@ -1215,7 +1228,7 @@ int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
 	    /* handle escape char */
 	    if (XIO_RDSTREAM(inpipe)->escape != -1) {
 	       /* check input data for escape char */
-	       unsigned char *ptr = *buff;
+	       unsigned char *ptr = buff;
 	       size_t ctr = 0;
 	       while (ctr < bytes) {
 		  if (*ptr == XIO_RDSTREAM(inpipe)->escape) {
@@ -1251,8 +1264,8 @@ int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
 	       size_t j;
 	       size_t N = 16;
 	       const unsigned char *end, *s, *t;
-	       s = *buff;
-	       end = (*buff)+bytes;
+	       s = buff;
+	       end = buff+bytes;
 	       xioprintblockheader(stderr, bytes, righttoleft);
 	       while (s < end) {
 		  /*! prefix? */
@@ -1298,8 +1311,8 @@ int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
 	       size_t i = 0;
 	       xioprintblockheader(stderr, bytes, righttoleft);
 	       while (i < (size_t)bytes) {
-		  int c = (*buff)[i];
-		  if (i > 0 && (*buff)[i-1] == '\n')
+		  int c = buff[i];
+		  if (i > 0 && buff[i-1] == '\n')
 		     /*! prefix? */;
 		  switch (c) {
 		  case '\a' : fputs("\\a", stderr); break;
@@ -1323,12 +1336,12 @@ int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
 	       /* print prefix */
 	       xioprintblockheader(stderr, bytes, righttoleft);
 	       for (i = 0; i < bytes; ++i) {
-		  fprintf(stderr, " %02x", (*buff)[i]);
+		  fprintf(stderr, " %02x", buff[i]);
 	       }
 	       fputc('\n', stderr);
 	    }
 
-	    writt = xiowrite(outpipe, *buff, bytes);
+	    writt = xiowrite(outpipe, buff, bytes);
 	    if (writt < 0) {
 	       /* EAGAIN when nonblocking but a mandatory lock is on file.
 		  the problem with EAGAIN is that the read cannot be repeated,
@@ -1355,11 +1368,9 @@ int xiotransfer(xiofile_t *inpipe, xiofile_t *outpipe,
 /* converts the newline characters (or character sequences) from the one
    specified in lineterm1 to that of lineterm2. Possible values are
    LINETERM_CR, LINETERM_CRNL, LINETERM_RAW.
-   buff points to the malloc()'ed data, input and output. It may be subject to
-   realloc(). bytes specifies the number of bytes input and output */
-int cv_newline(unsigned char **buff, ssize_t *bufsiz,
+   bytes specifies the number of bytes input and output */
+int cv_newline(unsigned char *buff, ssize_t *bytes,
 	       int lineterm1, int lineterm2) {
-   ssize_t *bytes = bufsiz;
    /* must perform newline changes */
    if (lineterm1 <= LINETERM_CR && lineterm2 <= LINETERM_CR) {
       /* no change in data length */
@@ -1369,23 +1380,23 @@ int cv_newline(unsigned char **buff, ssize_t *bufsiz,
       } else {
 	 from = '\r'; to = '\n';
       }
-      z = *buff + *bytes;
-      p = *buff;
+      z = buff + *bytes;
+      p = buff;
       while (p < z) {
 	 if (*p == from)  *p = to;
 	 ++p;
       }
 
    } else if (lineterm1 == LINETERM_CRNL) {
-      /* buffer becomes shorter */
+      /* buffer might become shorter */
       unsigned char to,  *s, *t, *z;
       if (lineterm2 == LINETERM_RAW) {
 	 to = '\n';
       } else {
 	 to = '\r';
       }
-      z = *buff + *bytes;
-      s = t = *buff;
+      z = buff + *bytes;
+      s = t = buff;
       while (s < z) {
 	 if (*s == '\r') {
 	    ++s;
@@ -1397,20 +1408,24 @@ int cv_newline(unsigned char **buff, ssize_t *bufsiz,
 	    *t++ = *s++;
 	 }
       }
-      *bufsiz = t - *buff;
+      *bytes = t - buff;
    } else {
-      /* buffer becomes longer, must alloc another space */
-      unsigned char *buf2;
+      /* buffer becomes longer (up to double length), must alloc another space */
+      static unsigned char *buf2;	/*! not threadsafe */
       unsigned char from;  unsigned char *s, *t, *z;
+
       if (lineterm1 == LINETERM_RAW) {
 	 from = '\n';
       } else {
 	 from = '\r';
       }
-      if ((buf2 = Malloc(2*socat_opts.bufsiz/*sic!*/+1)) == NULL) {
-	 return -1;
+      if (buf2 == NULL) {
+	 if ((buf2 = Malloc(socat_opts.bufsiz)) == NULL) {
+	    return -1;
+	 }
       }
-      s = *buff;  t = buf2;  z = *buff + *bytes;
+      memcpy(buf2, buff, *bytes);
+      s = buf2;  t = buff;  z = buf2 + *bytes;
       while (s < z) {
 	 if (*s == from) {
 	    *t++ = '\r'; *t++ = '\n';
@@ -1420,9 +1435,7 @@ int cv_newline(unsigned char **buff, ssize_t *bufsiz,
 	    *t++ = *s++;
 	 }
       }
-      free(*buff);
-      *buff = buf2;
-      *bufsiz = t - buf2;;
+      *bytes = t - buff;;
    }
    return 0;
 }
diff --git a/sycls.c b/sycls.c
index 0767f57..60d3682 100644
--- a/sycls.c
+++ b/sycls.c
@@ -23,6 +23,16 @@
 
 #if WITH_SYCLS
 
+#if HAVE_PROTOTYPE_LIB_posix_memalign
+int Posix_memalign(void **memptr, size_t alignment, size_t size) {
+   int result;
+   Debug3("posix_memalign(%p, "F_Zu", F_Zu)", memptr, alignment, size);
+   result = posix_memalign(memptr, alignment, size);
+   Debug1("posix_memalign(...) -> %d", result);
+   return result;
+}
+#endif /* HAVE_PROTOTYPE_LIB_posix_memalign */
+
 mode_t Umask(mode_t mask) {
    mode_t result;
    int _errno;
diff --git a/sycls.h b/sycls.h
index 2d5e706..8bbcc45 100644
--- a/sycls.h
+++ b/sycls.h
@@ -11,6 +11,7 @@ struct utsname;
 struct flock;
 struct addrinfo;
 
+int Posix_memalign(void **memptr, size_t alignment, size_t size);
 mode_t Umask(mode_t mask);
 #endif /* WITH_SYCLS */
 int Open(const char *pathname, int flags, mode_t mode);
@@ -175,6 +176,7 @@ void Add_history(const char *string);
 
 #else /* !WITH_SYCLS */
 
+#define Posix_memalign(m,a,s) posix_memalign(m,a,s)
 #define Umask(m) umask(m)
 #define Creat(p,m) creat(p,m)
 #define Lseek(f,o,w) lseek(f,o,w)
diff --git a/test.sh b/test.sh
index a775122..25cbae0 100755
--- a/test.sh
+++ b/test.sh
@@ -13614,7 +13614,7 @@ NAME=SCTP_SERVICENAME
 case "$TESTS" in
 *%$N%*|*%functions%*|*%socket%*|*%sctp%*|*%$NAME%*)
 TEST="$NAME: Service name resolution works with SCTP"
-# invoke socat with address SCTP4-CONNECT:$LOCALHOST:http; when this does fails with
+# invoke socat with address SCTP4-CONNECT:$LOCALHOST:http; when this fails with
 # "Connection refused", or does not fail at all, the test succeeded
 if ! eval $NUMCOND; then :;
 elif ! runssctp4 "$((PORT))" >/dev/null; then
@@ -13647,6 +13647,62 @@ esac
 N=$((N+1))
 
 
+# Test the o-direct option on reading
+NAME=O_DIRECT
+case "$TESTS" in
+*%$N%*|*%functions%*|*%engine%*|*%file%*|*%$NAME%*)
+TEST="$NAME: echo via file with o-direct"
+# Write data to a file and read it with options o-direct (and ignoreeof)
+# When the data read is the same as the data written the test succeeded.
+if ! eval $NUMCOND; then :;
+elif ! testoptions o-direct >/dev/null; then
+    $PRINTF "test $F_n $TEST... ${YELLOW}o-direct not available${NORMAL}\n" $N
+    numCANT=$((numCANT+1))
+    listCANT="$listCANT $N"
+else
+tf="$td/test$N.file"
+to="$td/test$N.stdout"
+te="$td/test$N.stderr"
+tdiff="$td/test$N.diff"
+da="test$N $(date) $RANDOM"
+$PRINTF "test $F_n $TEST... " $N
+CMD="$TRACE $SOCAT $opts - $tf,o-direct,ignoreeof!!$tf"
+echo "$da" |$CMD >"$to" 2>"$te"
+rc=$?
+if [ $rc -ne 0 ] && grep -q "Invalid argument" "$te" && [ $UNAME = Linux ]; then
+    case $(stat -f /tmp/gerhard/ |grep -o "Type: [^[:space:]]*" |cut -c 7-) in
+	ext2/ext3|xfs|reiserfs)
+	    $PRINTF "${FAILED}\n"
+	    echo "$CMD" >&2
+	    cat "$te" >&2
+	    numFAIL=$((numFAIL+1))
+	    listFAIL="$listFAIL $N" ;;
+	*) $PRINTF "${YELLOW}inable file system${NORMAL}\n"
+	    numCANT=$((numCANT+1))
+	    listCANT="$listCANT $N" ;;
+    esac
+elif [ $rc -ne 0 ]; then
+    $PRINTF "${FAILED}:\n"
+    echo "$CMD" >&2
+    cat "$te" >&2
+    numFAIL=$((numFAIL+1))
+    listFAIL="$listFAIL $N"
+elif ! echo "$da" |diff - "$to" >$tdiff; then
+    $PRINTF "${FAILED}\n"
+    echo "$CMD" >&2
+    cat "$te" >&2
+    cat "$tdiff" >&2
+    numFAIL=$((numFAIL+1))
+    listFAIL="$listFAIL $N"
+else
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+fi # command ok
+fi ;; # NUMCOND, feats
+esac
+N=$((N+1))
+
+
 ##################################################################################
 #=================================================================================
 # here come tests that might affect your systems integrity. Put normal tests