From 486cdf21583e5b1fad488a3e4f0a5242a31c0ffa Mon Sep 17 00:00:00 2001 From: Mathieu Xhonneux Date: Thu, 26 Jul 2018 02:10:40 +0000 Subject: bpf: add End.DT6 action to bpf_lwt_seg6_action helper The seg6local LWT provides the End.DT6 action, which allows to decapsulate an outer IPv6 header containing a Segment Routing Header (SRH), full specification is available here: https://tools.ietf.org/html/draft-filsfils-spring-srv6-network-programming-05 This patch adds this action now to the seg6local BPF interface. Since it is not mandatory that the inner IPv6 header also contains a SRH, seg6_bpf_srh_state has been extended with a pointer to a possible SRH of the outermost IPv6 header. This helps assessing if the validation must be triggered or not, and avoids some calls to ipv6_find_hdr. v3: s/1/true, s/0/false for boolean values v2: - changed true/false -> 1/0 - preempt_enable no longer called in first conditional block Signed-off-by: Mathieu Xhonneux Signed-off-by: Daniel Borkmann --- net/ipv6/seg6_local.c | 50 ++++++++++++++++++++++++++++++++------------------ 1 file changed, 32 insertions(+), 18 deletions(-) (limited to 'net/ipv6') diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c index e1025b493a18..60325dbfe88b 100644 --- a/net/ipv6/seg6_local.c +++ b/net/ipv6/seg6_local.c @@ -459,36 +459,57 @@ drop: DEFINE_PER_CPU(struct seg6_bpf_srh_state, seg6_bpf_srh_states); +bool seg6_bpf_has_valid_srh(struct sk_buff *skb) +{ + struct seg6_bpf_srh_state *srh_state = + this_cpu_ptr(&seg6_bpf_srh_states); + struct ipv6_sr_hdr *srh = srh_state->srh; + + if (unlikely(srh == NULL)) + return false; + + if (unlikely(!srh_state->valid)) { + if ((srh_state->hdrlen & 7) != 0) + return false; + + srh->hdrlen = (u8)(srh_state->hdrlen >> 3); + if (!seg6_validate_srh(srh, (srh->hdrlen + 1) << 3)) + return false; + + srh_state->valid = true; + } + + return true; +} + static int input_action_end_bpf(struct sk_buff *skb, struct seg6_local_lwt *slwt) { struct seg6_bpf_srh_state *srh_state = this_cpu_ptr(&seg6_bpf_srh_states); - struct seg6_bpf_srh_state local_srh_state; struct ipv6_sr_hdr *srh; - int srhoff = 0; int ret; srh = get_and_validate_srh(skb); - if (!srh) - goto drop; + if (!srh) { + kfree_skb(skb); + return -EINVAL; + } advance_nextseg(srh, &ipv6_hdr(skb)->daddr); /* preempt_disable is needed to protect the per-CPU buffer srh_state, * which is also accessed by the bpf_lwt_seg6_* helpers */ preempt_disable(); + srh_state->srh = srh; srh_state->hdrlen = srh->hdrlen << 3; - srh_state->valid = 1; + srh_state->valid = true; rcu_read_lock(); bpf_compute_data_pointers(skb); ret = bpf_prog_run_save_cb(slwt->bpf.prog, skb); rcu_read_unlock(); - local_srh_state = *srh_state; - preempt_enable(); - switch (ret) { case BPF_OK: case BPF_REDIRECT: @@ -500,24 +521,17 @@ static int input_action_end_bpf(struct sk_buff *skb, goto drop; } - if (unlikely((local_srh_state.hdrlen & 7) != 0)) - goto drop; - - if (ipv6_find_hdr(skb, &srhoff, IPPROTO_ROUTING, NULL, NULL) < 0) - goto drop; - srh = (struct ipv6_sr_hdr *)(skb->data + srhoff); - srh->hdrlen = (u8)(local_srh_state.hdrlen >> 3); - - if (!local_srh_state.valid && - unlikely(!seg6_validate_srh(srh, (srh->hdrlen + 1) << 3))) + if (srh_state->srh && !seg6_bpf_has_valid_srh(skb)) goto drop; + preempt_enable(); if (ret != BPF_REDIRECT) seg6_lookup_nexthop(skb, NULL, 0); return dst_input(skb); drop: + preempt_enable(); kfree_skb(skb); return -EINVAL; } -- cgit v1.2.3-59-g8ed1b