From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yan Zheng Subject: Re: [PATCH 2/2][MCAST] Fix for add_grec(...) Date: Thu, 10 Nov 2005 09:20:33 +0800 Message-ID: <4372A061.2030106@21cn.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: To: David Stevens In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org David Stevens wrote: > Yan, > I think your patch has some problems. > > Yan Zheng wrote on 11/09/2005 03:58:20 AM: > > >>+#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. > > >> 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) : > > >>+ (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.)