On Tue, 2024-12-10 at 11:18 +0200, Nikolay Aleksandrov wrote: > On 12/9/24 00:18, Radu Rendec wrote: > > The bridge input code may drop frames for various reasons and at various > > points in the ingress handling logic. Currently kfree_skb() is used > > everywhere, and therefore no drop reason is specified. Add drop reasons > > to the most common drop points. > > > > The purpose of this patch is to address the most common drop points on > > the bridge ingress path. It does not exhaustively add drop reasons to > > the entire bridge code. The intention here is to incrementally add drop > > reasons to the rest of the bridge code in follow up patches. > > > > Most of the skb drop points that are addressed in this patch can be > > easily tested by sending crafted packets. The diagram below shows a > > simple test configuration, and some examples using `packit`(*) are > > also included. The bridge is set up with STP disabled. > > (*) https://github.com/resurrecting-open-source-projects/packit > > > > The following changes were *not* tested: > > * SKB_DROP_REASON_BRIDGE_NO_EGRESS_PORT in br_multicast_flood(). I could > > not find an easy way to make a crafted packet get there. > > * SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD in br_handle_frame_finish() > > when the port state is BR_STATE_DISABLED, because in that case the > > frame is already dropped in the switch/case block at the end of > > br_handle_frame(). > > > > +---+---+ > > | br0 | > > +---+---+ > > | > > +---+---+ veth pair +-------+ > > | veth0 +-------------+ xeth0 | > > +-------+ +-------+ > > > > SKB_DROP_REASON_MAC_INVALID_SOURCE - br_handle_frame() > > packit -t UDP -s 192.168.0.1 -d 192.168.0.2 -S 8000 -D 8000 \ > > -e 01:22:33:44:55:66 -E aa:bb:cc:dd:ee:ff -c 1 \ > > -p '0x de ad be ef' -i xeth0 > > > > SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL - br_handle_frame() > > packit -t UDP -s 192.168.0.1 -d 192.168.0.2 -S 8000 -D 8000 \ > > -e 02:22:33:44:55:66 -E 01:80:c2:00:00:01 -c 1 \ > > -p '0x de ad be ef' -i xeth0 > > > > SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD - br_handle_frame() > > bridge link set dev veth0 state 0 # disabled > > packit -t UDP -s 192.168.0.1 -d 192.168.0.2 -S 8000 -D 8000 \ > > -e 02:22:33:44:55:66 -E aa:bb:cc:dd:ee:ff -c 1 \ > > -p '0x de ad be ef' -i xeth0 > > > > SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD - br_handle_frame_finish() > > bridge link set dev veth0 state 2 # learning > > packit -t UDP -s 192.168.0.1 -d 192.168.0.2 -S 8000 -D 8000 \ > > -e 02:22:33:44:55:66 -E aa:bb:cc:dd:ee:ff -c 1 \ > > -p '0x de ad be ef' -i xeth0 > > > > SKB_DROP_REASON_BRIDGE_NO_EGRESS_PORT - br_flood() > > packit -t UDP -s 192.168.0.1 -d 192.168.0.2 -S 8000 -D 8000 \ > > -e 02:22:33:44:55:66 -E aa:bb:cc:dd:ee:ff -c 1 \ > > -p '0x de ad be ef' -i xeth0 > > > > Signed-off-by: Radu Rendec <rrendec@xxxxxxxxxx> > > --- > > include/net/dropreason-core.h | 18 ++++++++++++++++++ > > net/bridge/br_forward.c | 4 ++-- > > net/bridge/br_input.c | 24 +++++++++++++++--------- > > 3 files changed, 35 insertions(+), 11 deletions(-) > > > > Hi, > Thanks for working on this, a few comments below. Sure, thanks for reviewing! Please see my comments below. > > diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h > > index c29282fabae6..1f2ae5b387c1 100644 > > --- a/include/net/dropreason-core.h > > +++ b/include/net/dropreason-core.h > > @@ -108,6 +108,9 @@ > > FN(TUNNEL_TXINFO) \ > > FN(LOCAL_MAC) \ > > FN(ARP_PVLAN_DISABLE) \ > > + FN(MAC_IEEE_MAC_CONTROL) \ > > + FN(BRIDGE_INGRESS_PORT_NFWD) \ > > + FN(BRIDGE_NO_EGRESS_PORT) \ > > FNe(MAX) > > > > /** > > @@ -502,6 +505,21 @@ enum skb_drop_reason { > > * enabled. > > */ > > SKB_DROP_REASON_ARP_PVLAN_DISABLE, > > + /** > > + * @SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL: the destination MAC address > > + * is an IEEE MAC Control address. > > + */ > > + SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL, > > + /** > > + * @SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD: the STP state of the > > + * ingress bridge port does not allow frames to be forwarded. > > + */ > > + SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD, > > Since this is used only when the port state causes the packet to drop, why not > rename it to something that suggests it was the state? Yes, Ido had a similar suggestion [1], so it's clear that it must be renamed. I will go with SKB_DROP_REASON_BRIDGE_INGRESS_STP_STATE in the next version, unless you have a better idea. > > + /** > > + * SKB_DROP_REASON_BRIDGE_NO_EGRESS_PORT: no eligible egress port was > > + * found while attempting to flood the frame. > > + */ > > + SKB_DROP_REASON_BRIDGE_NO_EGRESS_PORT, > > /** > > * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which > > * shouldn't be used as a real 'reason' - only for tracing code gen > > diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c > > index e19b583ff2c6..e33e2f4fc3d9 100644 > > --- a/net/bridge/br_forward.c > > +++ b/net/bridge/br_forward.c > > @@ -249,7 +249,7 @@ void br_flood(struct net_bridge *br, struct sk_buff *skb, > > > > out: > > if (!local_rcv) > > - kfree_skb(skb); > > + kfree_skb_reason(skb, SKB_DROP_REASON_BRIDGE_NO_EGRESS_PORT); > > This is not entirely correct, we can get here if we had an error forwarding > the packet to some port, but it may already have been forwarded to others. > The reason should distinguish between those two cases. I will follow Ido's suggestion [2] and rename SKB_DROP_REASON_VXLAN_NO_REMOTE to SKB_DROP_REASON_NO_TX_TARGET, and then use that. But it will only cover the case when there are no errors, so I still need a different reason for the error case. I looked, and I couldn't find an existing one that's close enough, so I think I should create a new one. How about SKB_DROP_REASON_TX_ERROR? I would not use "BRIDGE" in the name because I'm thinking it may be reused elsewhere, outside the bridge module. > > } > > > > #ifdef CONFIG_BRIDGE_IGMP_SNOOPING > > @@ -349,6 +349,6 @@ void br_multicast_flood(struct net_bridge_mdb_entry *mdst, > > > > out: > > if (!local_rcv) > > - kfree_skb(skb); > > + kfree_skb_reason(skb, SKB_DROP_REASON_BRIDGE_NO_EGRESS_PORT); > > Same comment as above (br_flood). > > > } > > #endif > > diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c > > index ceaa5a89b947..fc00e172e1e1 100644 > > --- a/net/bridge/br_input.c > > +++ b/net/bridge/br_input.c > > @@ -96,8 +96,10 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb > > if (br_mst_is_enabled(br)) { > > state = BR_STATE_FORWARDING; > > } else { > > - if (p->state == BR_STATE_DISABLED) > > - goto drop; > > + if (p->state == BR_STATE_DISABLED) { > > + kfree_skb_reason(skb, SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD); > > + return 0; > > + } > > > > state = p->state; > > } > > @@ -155,8 +157,10 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb > > } > > } > > > > - if (state == BR_STATE_LEARNING) > > - goto drop; > > + if (state == BR_STATE_LEARNING) { > > + kfree_skb_reason(skb, SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD); > > + return 0; > > + }> > > BR_INPUT_SKB_CB(skb)->brdev = br->dev; > > BR_INPUT_SKB_CB(skb)->src_port_isolated = !!(p->flags & BR_ISOLATED); > > @@ -331,8 +335,10 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb) > > if (unlikely(skb->pkt_type == PACKET_LOOPBACK)) > > return RX_HANDLER_PASS; > > > > - if (!is_valid_ether_addr(eth_hdr(skb)->h_source)) > > - goto drop; > > + if (!is_valid_ether_addr(eth_hdr(skb)->h_source)) { > > + kfree_skb_reason(skb, SKB_DROP_REASON_MAC_INVALID_SOURCE); > > + return RX_HANDLER_CONSUMED; > > + } > > > > skb = skb_share_check(skb, GFP_ATOMIC); > > if (!skb) > > @@ -374,7 +380,8 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb) > > return RX_HANDLER_PASS; > > > > case 0x01: /* IEEE MAC (Pause) */ > > - goto drop; > > + kfree_skb_reason(skb, SKB_DROP_REASON_MAC_IEEE_MAC_CONTROL); > > + return RX_HANDLER_CONSUMED; > > > > case 0x0E: /* 802.1AB LLDP */ > > fwd_mask |= p->br->group_fwd_mask; > > @@ -423,8 +430,7 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb) > > > > return nf_hook_bridge_pre(skb, pskb); > > default: > > -drop: > > - kfree_skb(skb); > > + kfree_skb_reason(skb, SKB_DROP_REASON_BRIDGE_INGRESS_PORT_NFWD); > > } > > return RX_HANDLER_CONSUMED; > > } [1] https://lore.kernel.org/bridge/Z1sLyqZQCjbcCOde@shredder/ [2] https://lore.kernel.org/bridge/Z1sUsSFfBC9GoiIA@shredder/ -- Best regards, Radu
