[ovs-dev] [PATCH] tun-metadata: Use correct offset when accessing fragmented metadata.

[Jesse Gross]

Since tunnel metadata is stored in a fixed area in the flow match field, we
must allocate space for options as they are registered with the switch. In order
to avoid exposing implementation complexity to the controller, we support
fragmentation when we run out of contiguous blocks that are large enough to
handle new requests.

When reading or writing to these fragmented blocks, there is a bug that would
cause us to keep on using the area after the allocated space rather than moving
to the next offset. This corrects that to use the offset for each block.

Unfortunately, while we did have a test for this exact use case, since the same
bug was present in both reading and writing code, everything appeared to work
as normal from the outside.

Signed-off-by: Jesse Gross <jesse at kernel.org>
---
 lib/tun-metadata.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/tun-metadata.c b/lib/tun-metadata.c
index a773aea..7a2a84f 100644
--- a/lib/tun-metadata.c
+++ b/lib/tun-metadata.c
@@ -490,7 +490,7 @@ memcpy_to_metadata(struct tun_metadata *dst, const void *src,
     int addr = 0;
 
     while (chain) {
-        memcpy(dst->opts.u8 + loc->c.offset + addr, (uint8_t *)src + addr,
+        memcpy(dst->opts.u8 + chain->offset, (uint8_t *)src + addr,
                chain->len);
         addr += chain->len;
         chain = chain->next;
@@ -507,7 +507,7 @@ memcpy_from_metadata(void *dst, const struct tun_metadata *src,
     int addr = 0;
 
     while (chain) {
-        memcpy((uint8_t *)dst + addr, src->opts.u8 + loc->c.offset + addr,
+        memcpy((uint8_t *)dst + addr, src->opts.u8 + chain->offset,
                chain->len);
         addr += chain->len;
         chain = chain->next;
-- 
2.5.0