Re: [PATCH 2/2][MCAST] Fix for add_grec(...)

David Stevens wrote:

Yan,
        I think your patch has some problems.

Yan Zheng [off-list ref] wrote on 11/09/2005 03:58:20 AM:

quoted

+#if 0
   if (!*psf_list) {
      if (type == MLD2_ALLOW_NEW_SOURCES ||
          type == MLD2_BLOCK_OLD_SOURCES)

@@ -1474,12 +1477,15 @@ static struct sk_buff *add_grec(struct s
      }
      return skb;
   }
+#endif

        This code is the only place in the current code where you
can generate a group header with an empty source list (what it is
checking for). Your patch has added an add_grhead() for change
and EXCLUDE records, but it isn't checking mca_crcount or isquery.
I need to check, but I'm concerned this will create a group header
in a report for cases where it should not.

ischange implicits mca_crcount has already been ckecked in mld_send_cr(...)
Actually, check mca_crcount directly will get mode change report sent one times less 
than you intend, because mca_crcount has decreased by one before call add_grec(...).


Now We only have MLD2_MODE_IS_INCLUDE left. but "mode is include and source list is empty"
is an impossible event.

quoted

   pmr = skb ? (struct mld2_report *)skb->h.raw : NULL;

   /* EX and TO_EX get a fresh packet, if needed */
-   if (truncate) {
-      if (pmr && pmr->ngrec &&
-          AVAILABLE(skb) < grec_size(pmc, type, gdeleted, sdeleted)) {
+   if (truncate || ischange) {
+      int min_len;
+      min_len   = truncate ? grec_size(pmc, type, gdeleted, sdeleted) : 

quoted

+           (sizeof(struct mld2_grec) + sizeof(struct in6_addr));
+      if (pmr && pmr->ngrec && AVAILABLE(skb) < min_len) {
         if (skb)
            mld_sendpack(skb);
         skb = mld_newpack(dev, dev->mtu);

        This "truncate" code is to handle exclude records that may be
truncated. It gets a new packet when adding this record and the whole
thing won't fit in a single packet. This is not appropriate for anything
but IS_EX and TO_EX, but "ischange" in your patch will be true for
TO_IN. So, I think this will waste space in a report that could hold
some of these TO_IN sources.

When type is MLD2_MODE_IS_INCLUDE, min_len is equal to "sizeof(struct mld2_grec) + 
sizeof(struct in6_addr)". it satisfies the comment above. (make sure we have room 
for group header and at least one source.)