From 74e31ca850c1cddeca03503171dd145b6ce293b6 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Tue, 19 Feb 2019 19:53:02 +0100 Subject: [PATCH] bpf: add skb->queue_mapping write access from tc clsact The skb->queue_mapping already have read access, via __sk_buff->queue_mapping. This patch allow BPF tc qdisc clsact write access to the queue_mapping via tc_cls_act_is_valid_access. Also handle that the value NO_QUEUE_MAPPING is not allowed. It is already possible to change this via TC filter action skbedit tc-skbedit(8). Due to the lack of TC examples, lets show one: # tc qdisc add dev ixgbe1 clsact # tc filter add dev ixgbe1 ingress matchall action skbedit queue_mapping 5 # tc filter list dev ixgbe1 ingress The most common mistake is that XPS (Transmit Packet Steering) takes precedence over setting skb->queue_mapping. XPS is configured per DEVICE via /sys/class/net/DEVICE/queues/tx-*/xps_cpus via a CPU hex mask. To disable set mask=00. The purpose of changing skb->queue_mapping is to influence the selection of the net_device "txq" (struct netdev_queue), which influence selection of the qdisc "root_lock" (via txq->qdisc->q.lock) and txq->_xmit_lock. When using the MQ qdisc the txq->qdisc points to different qdiscs and associated locks, and HARD_TX_LOCK (txq->_xmit_lock), allowing for CPU scalability. Due to lack of TC examples, lets show howto attach clsact BPF programs: # tc qdisc add dev ixgbe2 clsact # tc filter add dev ixgbe2 egress bpf da obj XXX_kern.o sec tc_qmap2cpu # tc filter list dev ixgbe2 egress Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann --- net/core/filter.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index b584cb42a803..85749f6ec789 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6279,6 +6279,7 @@ static bool tc_cls_act_is_valid_access(int off, int size, case bpf_ctx_range(struct __sk_buff, tc_classid): case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]): case bpf_ctx_range(struct __sk_buff, tstamp): + case bpf_ctx_range(struct __sk_buff, queue_mapping): break; default: return false; @@ -6683,9 +6684,18 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, break; case offsetof(struct __sk_buff, queue_mapping): - *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, - bpf_target_off(struct sk_buff, queue_mapping, 2, - target_size)); + if (type == BPF_WRITE) { + *insn++ = BPF_JMP_IMM(BPF_JGE, si->src_reg, NO_QUEUE_MAPPING, 1); + *insn++ = BPF_STX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct sk_buff, + queue_mapping, + 2, target_size)); + } else { + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct sk_buff, + queue_mapping, + 2, target_size)); + } break; case offsetof(struct __sk_buff, vlan_present): -- 2.34.1