On 2019/01/18 4:19, Cong Wang wrote: > On Thu, Jan 17, 2019 at 12:59 AM Toshiaki Makita > <makita.toshiaki@xxxxxxxxxxxxx> wrote: >> On 2019/01/17 17:17, Zahari Doychev wrote: >>> On Tue, Jan 15, 2019 at 03:11:28PM +0900, Toshiaki Makita wrote: >>>> On 2019/01/13 22:59, Zahari Doychev wrote: >>>>> Use the skb->mac_len instead of using the ETH_HLEN when pushing the skb >>>>> data pointer. This fixes sending incorrect packets when more than one >>>>> vlan tags are pushed by tc-vlan and the mac header length is bigger than >>>>> ETH_HLEN. In this way the vlan tagged contained in the skb is inserted at >>>>> right offset in the packet payload before sending the packet. >>>>> >>>>> Signed-off-by: Zahari Doychev <zahari.doychev@xxxxxxxxx> >>>>> --- >>>>> net/bridge/br_forward.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c >>>>> index 5372e2042adf..55f928043f77 100644 >>>>> --- a/net/bridge/br_forward.c >>>>> +++ b/net/bridge/br_forward.c >>>>> @@ -39,7 +39,7 @@ int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb >>>>> if (!is_skb_forwardable(skb->dev, skb)) >>>>> goto drop; >>>>> >>>>> - skb_push(skb, ETH_HLEN); >>>>> + skb_push(skb, skb->mac_len); >>>>> br_drop_fake_rtable(skb); >>>>> >>>>> if (skb->ip_summed == CHECKSUM_PARTIAL && >>>>> >>>> >>>> I guess you mean skb->data points to mac_header + ETH_HLEN + VLAN_HLEN >>>> when bridge receives skbs in br_handle_frame()? >>> >>> yes, this is what I see. >>> >>>> If so, the behavior of act_vlan is odd. Normal double tagged skbs from >>>> hardware devices should have skb->data pointing to mac_header + ETH_HLEN >>>> because they just call eth_type_trans() before entering >>>> netif_receive_skb()... >>>> I think act_vlan needs some fix. >>> >>> The act_valn is using the skb_vlan_push(...) to add the vlan tags and in this >>> way increasing the skb->data and mac_len. So I think I can add a fix there to >>> set the skb->data to point to mac_header + ETH_HLEN when more tags are added. >> >> As skb->data always points to mac_header after calling skb_vlan_push(), >> we probably need to remember mac_len before invocation of it? >> >> The problem should be this part in tcf_vlan_act(): >> >>> out: >>> if (skb_at_tc_ingress(skb)) >>> skb_pull_rcsum(skb, skb->mac_len); >> >> skb->mac_len should not be used here. > > I am confused. This code is to push skb->data back to network header. > If skb_vlan_push() pushes skb->data to mac header, then this code > is correct for pulling it back to network header, as skb->mac_len is > updated accordingly inside skb_vlan_push() too. > > What goes wrong here? skb->mac_len isn't correct for double tagging? Bridge and VLAN code (skb_vlan_untag in __netif_receive_skb_core) expects skb->data to point to the start of VLAN header, not the next (network) header. After calling tcf_vlan_act() on ingress filter, skb->data points to the next of VLAN header (network header), while non-hwaccel VLAN packets (including double tagged ones) from NIC drivers have skb->data pointing to the start of VLAN header as expected. I'm not sure if mac_len should or should not be updated in skb_vlan_push(). Anyway IIRC skb_vlan_untag() and bridge code do not rely on mac_len so mac_len should not cause problems there. -- Toshiaki Makita
