Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge
Ingo Oeser wrote: > On Saturday 26 May 2007, Patrick McHardy wrote: > >>net/8021q ignores the VLAN header overhead, so we should probably do the >>same here for consistency. Using IS_VLAN_IP (and IS_PPPOE_IP for current >>-rc) looks fine, additionally we should probably also check for >>skb->nfct != NULL to make sure that at least without connection tracking >>the bridge doesn't perform fragmentation. > > > And could we separe the conditions for that into a static helper function > explaining each of these conditions? e.g. sth. like that: The MTU checks are self-explanatory. Just a comment above the function stating that it tries to find out whether a packet needs to be refragmented because it was defragmented by IPv4 connection tracking and exceeds the MTU should be enough. > static bool br_nf_need_fragment(struct sk_buff *skb) > { > /* Plain IP packet does not fit in MTU */ > if (!(skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu)) > return true; > > /* VLAN encapsulated IP packet does not fit in MTU */ > if (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN) > return true; > > /* PPPoE encapsulated IP packet does not fit in MTU */ > if (IS_PPPOE_IP(skb) && skb->len > skb->dev->mtu - PPPOE_SES_HLEN) > return true; > > return false; > } As I said, I don't think we should account for the VLAN header overhead, the VLAN code itself doesn't even do it. And we should exclude packets that don't have a connection tracking reference attached since we are only undoing the damage connection tracking did by defragmenting it and should avoid fragmenting other packets as good as possible. > and then br_nf_dev_queue_xmit() becomes: > > static int br_nf_dev_queue_xmit(struct sk_buff *skb) > { > if (br_nf_need_fragment(skb) && !skb_is_gso(skb)) > return ip_fragment(skb, br_dev_queue_push_xmit); > else > return br_dev_queue_push_xmit(skb); > } > > which is much more readable, more documented and doesn't contain a condition > monster :-) > > @Patrick: Could you check, wether the PPPoE case is correct? It looks OK. But there is another problem, ip_fragment doesn't care about the PPPoE overhead and produces a packet that will be too large after restoring the PPPoE header. A second __fake_rtable that accounts for the PPPoE overhead could probably fix that .. > What do you think? Should I submit a patch for that? Sure :) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge
On Saturday 26 May 2007, Patrick McHardy wrote: > Adam Osuchowski wrote: > > if (((skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu) || > > (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN)) && > > !skb_is_gso(skb)) > > return ip_fragment ... > > > net/8021q ignores the VLAN header overhead, so we should probably do the > same here for consistency. Using IS_VLAN_IP (and IS_PPPOE_IP for current > -rc) looks fine, additionally we should probably also check for > skb->nfct != NULL to make sure that at least without connection tracking > the bridge doesn't perform fragmentation. And could we separe the conditions for that into a static helper function explaining each of these conditions? e.g. sth. like that: static bool br_nf_need_fragment(struct sk_buff *skb) { /* Plain IP packet does not fit in MTU */ if (!(skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu)) return true; /* VLAN encapsulated IP packet does not fit in MTU */ if (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN) return true; /* PPPoE encapsulated IP packet does not fit in MTU */ if (IS_PPPOE_IP(skb) && skb->len > skb->dev->mtu - PPPOE_SES_HLEN) return true; return false; } and then br_nf_dev_queue_xmit() becomes: static int br_nf_dev_queue_xmit(struct sk_buff *skb) { if (br_nf_need_fragment(skb) && !skb_is_gso(skb)) return ip_fragment(skb, br_dev_queue_push_xmit); else return br_dev_queue_push_xmit(skb); } which is much more readable, more documented and doesn't contain a condition monster :-) @Patrick: Could you check, wether the PPPoE case is correct? What do you think? Should I submit a patch for that? Best Regards Ingo Oeser - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge
Adam Osuchowski wrote: > Stephen Hemminger wrote: > >>It would be better to account for the tag in the length check. >>Something like >> if (skb->protocol == htons(ETH_P_IP) && >> skb->len > skb->dev->mtu - (IS_VLAN_IP(skb) ? VLAN_HLEN : 0) && >> !skb_is_gso(skb)) >> return ip_fragment ... > > > It isn't good solution because one of IS_VLAN_IP() necessary condition is > > skb->protocol == htons(ETH_P_8021Q) > > which is, of course, mutually exclusive with > > skb->protocol == htons(ETH_P_IP) > > from br_nf_dev_queue_xmit(). IMHO, one should check length of ETH_P_IP > and ETH_P_8021Q frames separately: > > if (((skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu) || > (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN)) && > !skb_is_gso(skb)) > return ip_fragment ... net/8021q ignores the VLAN header overhead, so we should probably do the same here for consistency. Using IS_VLAN_IP (and IS_PPPOE_IP for current -rc) looks fine, additionally we should probably also check for skb->nfct != NULL to make sure that at least without connection tracking the bridge doesn't perform fragmentation. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge
Stephen Hemminger wrote: > It would be better to account for the tag in the length check. > Something like > if (skb->protocol == htons(ETH_P_IP) && > skb->len > skb->dev->mtu - (IS_VLAN_IP(skb) ? VLAN_HLEN : 0) && > !skb_is_gso(skb)) > return ip_fragment ... It isn't good solution because one of IS_VLAN_IP() necessary condition is skb->protocol == htons(ETH_P_8021Q) which is, of course, mutually exclusive with skb->protocol == htons(ETH_P_IP) from br_nf_dev_queue_xmit(). IMHO, one should check length of ETH_P_IP and ETH_P_8021Q frames separately: if (((skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu) || (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN)) && !skb_is_gso(skb)) return ip_fragment ... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge
On Fri, 25 May 2007 10:17:50 +0200 Adam Osuchowski <[EMAIL PROTECTED]> wrote: > There is a problem with fragmented IP packet sent within 802.1Q tagged > ethernet frame through bridge. Problem exists when conntrack is enabled > (i.e. nf_conntrack_ipv4 module is loaded). Then, such packets are not > fragmented again (after prior reassembling on bridge device) during > passing it to bridge enslaved NIC. It cause MTU exceeding and as a result > dropping packet. > > Problem exists from kernel version 2.6.17 to 2.6.21.3 inclusive. > > Below, there is a patch to fix it. > > Regards. > > > --- linux-2.6.21.3.orig/net/bridge/br_netfilter.c 2007-05-25 > 09:56:15.0 +0200 > +++ linux-2.6.21.3/net/bridge/br_netfilter.c 2007-05-25 10:11:42.0 > +0200 > @@ -731,7 +731,7 @@ > > static int br_nf_dev_queue_xmit(struct sk_buff *skb) > { > - if (skb->protocol == htons(ETH_P_IP) && > + if ((skb->protocol == htons(ETH_P_IP) || IS_VLAN_IP(skb)) && > skb->len > skb->dev->mtu && > !skb_is_gso(skb)) > return ip_fragment(skb, br_dev_queue_push_xmit); It would be better to account for the tag in the length check. Something like if (skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu - (IS_VLAN_IP(skb) ? VLAN_HLEN : 0) && !skb_is_gso(skb)) return ip_fragment ... -- Stephen Hemminger <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/