[nuttx] 01/02: mm/iob: Fix IOB length in `iob_reserve`

[xi...@apache.org]

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xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/nuttx.git

commit e2c9aa65883780747ca00625a1452dddc6f8a138
Author: Zhe Weng <we...@xiaomi.com>
AuthorDate: Thu Aug 17 15:55:32 2023 +0800

    mm/iob: Fix IOB length in `iob_reserve`
    
    If we apply `iob_reserve` on an IOB with `io_offset != 0`, the `head->io_pktlen` and `iob->io_len` will become wrong value, because we only need to trim `offset - iob->io_offset`.
    
    Signed-off-by: Zhe Weng <we...@xiaomi.com>
---
 mm/iob/iob_reserve.c | 32 +++++++++++++-------------------
 mm/iob/iob_test.c    | 20 ++++++++++++++++++++
 2 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/mm/iob/iob_reserve.c b/mm/iob/iob_reserve.c
index 2f459de3aa..e1964d5d14 100644
--- a/mm/iob/iob_reserve.c
+++ b/mm/iob/iob_reserve.c
@@ -41,20 +41,11 @@
 
 void iob_reserve(FAR struct iob_s *iob, unsigned int reserved)
 {
+  FAR struct iob_s *head = iob;
   unsigned int offset;
+  int trimlen;
 
-  /* Empty iob buffer is allowed, update packet length. */
-
-  if (iob->io_pktlen > reserved)
-    {
-      iob->io_pktlen -= reserved;
-    }
-  else
-    {
-      iob->io_pktlen = 0;
-    }
-
-  /* Update offset and reducing the tail room */
+  /* Update offset and adjust packet length. */
 
   while (iob != NULL && reserved > 0)
     {
@@ -67,16 +58,19 @@ void iob_reserve(FAR struct iob_s *iob, unsigned int reserved)
           offset = reserved;
         }
 
-      if (iob->io_len > offset)
-        {
-          iob->io_len -= offset;
-        }
-      else
+      trimlen = offset - iob->io_offset;
+
+      /* At most trim iob->io_len to 0. */
+
+      if ((int)(iob->io_len - trimlen) < 0)
         {
-          iob->io_len = 0;
+          trimlen = iob->io_len;
         }
 
-      iob->io_offset = offset;
+      head->io_pktlen -= trimlen;
+      iob->io_len     -= trimlen;
+      iob->io_offset   = offset;
+
       iob = iob->io_flink;
       reserved -= offset;
     }
diff --git a/mm/iob/iob_test.c b/mm/iob/iob_test.c
index 78122c0768..f865326385 100644
--- a/mm/iob/iob_test.c
+++ b/mm/iob/iob_test.c
@@ -161,6 +161,26 @@ int main(int argc, char **argv)
       fprintf(stderr, "Buffer1 does not match buffer2\n");
     }
 
+  nbytes = iob->io_pktlen;
+
+  iob_reserve(iob, 55);
+  printf("Reserve: adjust offset to 55\n");
+  dump_chain(iob);
+
+  if (iob->io_offset != 55 || iob->io_pktlen + 55 != nbytes)
+    {
+      fprintf(stderr, "Offset or packet length wrong\n");
+    }
+
+  iob_reserve(iob, 28);
+  printf("Reserve: adjust offset to 28\n");
+  dump_chain(iob);
+
+  if (iob->io_offset != 28 || iob->io_pktlen + 28 != nbytes)
+    {
+      fprintf(stderr, "Offset or packet length wrong\n");
+    }
+
   while (iob) iob = iob_free(iob);
   return EXIT_SUCCESS;
 }