On Sun, Apr 04, 2021 at 07:49:03AM +0200, Oleksij Rempel wrote: > Am 04.04.21 um 01:21 schrieb Vladimir Oltean: > > On Sat, Apr 03, 2021 at 05:05:34PM +0300, Vladimir Oltean wrote: > >> On Sat, Apr 03, 2021 at 01:48:40PM +0200, Oleksij Rempel wrote: > >>> Some switches (for example ar9331) do not provide enough information > >>> about forwarded packets. If the switch decision was made based on IPv4 > >>> or IPv6 header, we need to analyze it and set proper flag. > >>> > >>> Potentially we can do it in existing rcv path, on other hand we can > >>> avoid part of duplicated work and let the dsa framework set skb header > >>> pointers and then use preprocessed skb one step later withing the rcv_post > >>> call back. > >>> > >>> This patch is needed for ar9331 switch. > >>> > >>> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> > >>> --- > >> > >> I don't necessarily disagree with this, perhaps we can even move > >> Florian's dsa_untag_bridge_pvid() call inside a rcv_post() method > >> implemented by the DSA_TAG_PROTO_BRCM_LEGACY, DSA_TAG_PROTO_BRCM_PREPEND > >> and DSA_TAG_PROTO_BRCM taggers. Or even better, because Oleksij's > >> rcv_post is already prototype-compatible with dsa_untag_bridge_pvid, we > >> can already do: > >> > >> .rcv_post = dsa_untag_bridge_pvid, > >> > >> This should be generally useful for stuff that DSA taggers need to do > >> which is easiest done after eth_type_trans() was called. > > > > I had some fun with an alternative method of parsing the frame for IGMP > > so that you can clear skb->offload_fwd_mark, which doesn't rely on the > > introduction of a new method in DSA. It should also have several other > > advantages compared to your solution such as the fact that it should > > work with VLAN-tagged packets. > > > > Background: we made Receive Packet Steering work on DSA master interfaces > > (echo 3 > /sys/class/net/eth0/queues/rx-1/rps_cpus) even when the DSA > > tag shifts to the right the IP headers and everything that comes > > afterwards. The flow dissector had to be patched for that, just grep for > > DSA in net/core/flow_dissector.c. > > > > The problem you're facing is that you can't parse the IP and IGMP > > headers in the tagger's rcv() method, since the network header, > > transport header offsets and skb->protocol are all messed up, since > > eth_type_trans hasn't been called yet. > > > > And that's the trick right there, you're between a rock and a hard > > place: too early because eth_type_trans wasn't called yet, and too late > > because skb->dev was changed and no longer points to the DSA master, so > > the flow dissector adjustment we made doesn't apply. > > > > But if you call the flow dissector _before_ you call "skb->dev = > > dsa_master_find_slave" (and yes, while the DSA tag is still there), then > > it's virtually as if you had called that while the skb belonged to the > > DSA master, so it should work with __skb_flow_dissect. > > > > In fact I prototyped this idea below. I wanted to check whether I can > > match something as fine-grained as an IGMPv2 Membership Report message, > > and I could. > > > > I prototyped it inside the ocelot tagging protocol driver because that's > > what I had handy. I used __skb_flow_dissect with my own flow dissector > > which had to be initialized at the tagger module_init time, even though > > I think I could have probably just called skb_flow_dissect_flow_keys > > with a standard dissector, and that would have removed the need for the > > custom module_init in tag_ocelot.c. One thing that is interesting is > > that I had to add the bits for IGMP parsing to the flow dissector > > myself (based on the existing ICMP code). I was too lazy to do that for > > MLD as well, but it is really not hard. Or even better, if you don't > > need to look at all inside the IGMP/MLD header, I think you can even > > omit adding this parsing code to the flow dissector and just look at > > basic.n_proto and basic.ip_proto. > > > > See the snippet below. Hope it helps. > > > > -----------------------------[ cut here ]----------------------------- > > diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h > > index ffd386ea0dbb..4c25fa47637a 100644 > > --- a/include/net/flow_dissector.h > > +++ b/include/net/flow_dissector.h > > @@ -190,6 +190,20 @@ struct flow_dissector_key_icmp { > > u16 id; > > }; > > > > +/** > > + * flow_dissector_key_igmp: > > + * type: indicates the message type, see include/uapi/linux/igmp.h > > + * code: Max Resp Code, the maximum time in 1/10 second > > + * increments before sending a responding report > > + * group: the multicast address being queried when sending a > > + * Group-Specific or Group-and-Source-Specific Query. > > + */ > > +struct flow_dissector_key_igmp { > > + u8 type; > > + u8 code; /* Max Resp Time in IGMPv2 */ > > + __be32 group; > > +}; > > + > > /** > > * struct flow_dissector_key_eth_addrs: > > * @src: source Ethernet address > > @@ -259,6 +273,7 @@ enum flow_dissector_key_id { > > FLOW_DISSECTOR_KEY_PORTS, /* struct flow_dissector_key_ports */ > > FLOW_DISSECTOR_KEY_PORTS_RANGE, /* struct flow_dissector_key_ports */ > > FLOW_DISSECTOR_KEY_ICMP, /* struct flow_dissector_key_icmp */ > > + FLOW_DISSECTOR_KEY_IGMP, /* struct flow_dissector_key_igmp */ > > FLOW_DISSECTOR_KEY_ETH_ADDRS, /* struct flow_dissector_key_eth_addrs */ > > FLOW_DISSECTOR_KEY_TIPC, /* struct flow_dissector_key_tipc */ > > FLOW_DISSECTOR_KEY_ARP, /* struct flow_dissector_key_arp */ > > @@ -314,6 +329,7 @@ struct flow_keys { > > struct flow_dissector_key_keyid keyid; > > struct flow_dissector_key_ports ports; > > struct flow_dissector_key_icmp icmp; > > + struct flow_dissector_key_igmp igmp; > > /* 'addrs' must be the last member */ > > struct flow_dissector_key_addrs addrs; > > }; > > diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c > > index 5985029e43d4..8cc8c34ea5cd 100644 > > --- a/net/core/flow_dissector.c > > +++ b/net/core/flow_dissector.c > > @@ -202,6 +202,30 @@ static void __skb_flow_dissect_icmp(const struct sk_buff *skb, > > skb_flow_get_icmp_tci(skb, key_icmp, data, thoff, hlen); > > } > > > > +static void __skb_flow_dissect_igmp(const struct sk_buff *skb, > > + struct flow_dissector *flow_dissector, > > + void *target_container, const void *data, > > + int thoff, int hlen) > > +{ > > + struct flow_dissector_key_igmp *key_igmp; > > + struct igmphdr *ih, _ih; > > + > > + if (!dissector_uses_key(flow_dissector, FLOW_DISSECTOR_KEY_IGMP)) > > + return; > > + > > + ih = __skb_header_pointer(skb, thoff, sizeof(_ih), data, hlen, &_ih); > > + if (!ih) > > + return; > > + > > + key_igmp = skb_flow_dissector_target(flow_dissector, > > + FLOW_DISSECTOR_KEY_IGMP, > > + target_container); > > + > > + key_igmp->type = ih->type; > > + key_igmp->code = ih->code; > > + key_igmp->group = ih->group; > > +} > > + > > void skb_flow_dissect_meta(const struct sk_buff *skb, > > struct flow_dissector *flow_dissector, > > void *target_container) > > @@ -1398,6 +1422,11 @@ bool __skb_flow_dissect(const struct net *net, > > data, nhoff, hlen); > > break; > > > > + case IPPROTO_IGMP: > > + __skb_flow_dissect_igmp(skb, flow_dissector, target_container, > > + data, nhoff, hlen); > > + break; > > + > > default: > > break; > > } > > diff --git a/net/dsa/tag_ocelot.c b/net/dsa/tag_ocelot.c > > index f9df9cac81c5..a2cc824ddeec 100644 > > --- a/net/dsa/tag_ocelot.c > > +++ b/net/dsa/tag_ocelot.c > > @@ -2,9 +2,51 @@ > > /* Copyright 2019 NXP Semiconductors > > */ > > #include <linux/dsa/ocelot.h> > > +#include <linux/igmp.h> > > #include <soc/mscc/ocelot.h> > > #include "dsa_priv.h" > > > > +static const struct flow_dissector_key ocelot_flow_keys[] = { > > + { > > + .key_id = FLOW_DISSECTOR_KEY_CONTROL, > > + .offset = offsetof(struct flow_keys, control), > > + }, > > + { > > + .key_id = FLOW_DISSECTOR_KEY_BASIC, > > + .offset = offsetof(struct flow_keys, basic), > > + }, > > + { > > + .key_id = FLOW_DISSECTOR_KEY_IGMP, > > + .offset = offsetof(struct flow_keys, igmp), > > + }, > > +}; > > + > > +static struct flow_dissector ocelot_flow_dissector __read_mostly; > > + > > +static struct sk_buff *ocelot_drop_igmp(struct sk_buff *skb) > > +{ > > + struct flow_keys fk; > > + > > + memset(&fk, 0, sizeof(fk)); > > + > > + if (!__skb_flow_dissect(NULL, skb, &ocelot_flow_dissector, > > + &fk, NULL, 0, 0, 0, 0)) > > + return skb; > > + > > + if (fk.basic.n_proto != htons(ETH_P_IP)) > > + return skb; > > + > > + if (fk.basic.ip_proto != IPPROTO_IGMP) > > + return skb; > > + > > + if (fk.igmp.type != IGMPV2_HOST_MEMBERSHIP_REPORT) > > + return skb; > > + > > + skb_dump(KERN_ERR, skb, true); > > + > > + return NULL; > > +} > > + > > static void ocelot_xmit_ptp(struct dsa_port *dp, void *injection, > > struct sk_buff *clone) > > { > > @@ -84,6 +126,10 @@ static struct sk_buff *ocelot_rcv(struct sk_buff *skb, > > u8 *extraction; > > u16 vlan_tpid; > > > > + skb = ocelot_drop_igmp(skb); > > + if (!skb) > > + return NULL; > > I probably like this idea, but i need more understanding :) > > In case of ocelot_drop_igmp() you wont to really drop it? Or it is just > example on how it may potentially work? > I ask, because IGMP should not be dropped. Uhm, yeah, it is just an example of 'how to do X with IGMP packets from the DSA receive path'. You don't have to drop them.