From 3bd0b15281af776650e1550be4ea655b8cfa10c8 Mon Sep 17 00:00:00 2001 From: Peter Oskolkov Date: Wed, 13 Feb 2019 11:53:39 -0800 Subject: bpf: add handling of BPF_LWT_REROUTE to lwt_bpf.c This patch builds on top of the previous patch in the patchset, which added BPF_LWT_ENCAP_IP mode to bpf_lwt_push_encap. As the encapping can result in the skb needing to go via a different interface/route/dst, bpf programs can indicate this by returning BPF_LWT_REROUTE, which triggers a new route lookup for the skb. v8 changes: fix kbuild errors when LWTUNNEL_BPF is builtin, but IPV6 is a module: as LWTUNNEL_BPF can only be either Y or N, call IPV6 routing functions only if they are built-in. v9 changes: - fixed a kbuild test robot compiler warning; - call IPV6 routing functions via ipv6_stub. v10 changes: removed unnecessary IS_ENABLED and pr_warn_once. v11 changes: fixed a potential dst leak. Signed-off-by: Peter Oskolkov Signed-off-by: Alexei Starovoitov --- net/core/lwt_bpf.c | 126 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 124 insertions(+), 2 deletions(-) (limited to 'net/core') diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c index 079871fc020f..32251f3fcda0 100644 --- a/net/core/lwt_bpf.c +++ b/net/core/lwt_bpf.c @@ -17,6 +17,7 @@ #include #include #include +#include struct bpf_lwt_prog { struct bpf_prog *prog; @@ -56,6 +57,7 @@ static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt, switch (ret) { case BPF_OK: + case BPF_LWT_REROUTE: break; case BPF_REDIRECT: @@ -88,6 +90,30 @@ static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt, return ret; } +static int bpf_lwt_input_reroute(struct sk_buff *skb) +{ + int err = -EINVAL; + + if (skb->protocol == htons(ETH_P_IP)) { + struct iphdr *iph = ip_hdr(skb); + + err = ip_route_input_noref(skb, iph->daddr, iph->saddr, + iph->tos, skb_dst(skb)->dev); + } else if (skb->protocol == htons(ETH_P_IPV6)) { + err = ipv6_stub->ipv6_route_input(skb); + } else { + err = -EAFNOSUPPORT; + } + + if (err) + goto err; + return dst_input(skb); + +err: + kfree_skb(skb); + return err; +} + static int bpf_input(struct sk_buff *skb) { struct dst_entry *dst = skb_dst(skb); @@ -99,11 +125,11 @@ static int bpf_input(struct sk_buff *skb) ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT); if (ret < 0) return ret; + if (ret == BPF_LWT_REROUTE) + return bpf_lwt_input_reroute(skb); } if (unlikely(!dst->lwtstate->orig_input)) { - pr_warn_once("orig_input not set on dst for prog %s\n", - bpf->out.name); kfree_skb(skb); return -EINVAL; } @@ -148,6 +174,91 @@ static int xmit_check_hhlen(struct sk_buff *skb) return 0; } +static int bpf_lwt_xmit_reroute(struct sk_buff *skb) +{ + struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev); + int oif = l3mdev ? l3mdev->ifindex : 0; + struct dst_entry *dst = NULL; + struct sock *sk; + struct net *net; + bool ipv4; + int err; + + if (skb->protocol == htons(ETH_P_IP)) + ipv4 = true; + else if (skb->protocol == htons(ETH_P_IPV6)) + ipv4 = false; + else + return -EAFNOSUPPORT; + + sk = sk_to_full_sk(skb->sk); + if (sk) { + if (sk->sk_bound_dev_if) + oif = sk->sk_bound_dev_if; + net = sock_net(sk); + } else { + net = dev_net(skb_dst(skb)->dev); + } + + if (ipv4) { + struct iphdr *iph = ip_hdr(skb); + struct flowi4 fl4 = {}; + struct rtable *rt; + + fl4.flowi4_oif = oif; + fl4.flowi4_mark = skb->mark; + fl4.flowi4_uid = sock_net_uid(net, sk); + fl4.flowi4_tos = RT_TOS(iph->tos); + fl4.flowi4_flags = FLOWI_FLAG_ANYSRC; + fl4.flowi4_proto = iph->protocol; + fl4.daddr = iph->daddr; + fl4.saddr = iph->saddr; + + rt = ip_route_output_key(net, &fl4); + if (IS_ERR(rt)) + return -EINVAL; + dst = &rt->dst; + } else { + struct ipv6hdr *iph6 = ipv6_hdr(skb); + struct flowi6 fl6 = {}; + + fl6.flowi6_oif = oif; + fl6.flowi6_mark = skb->mark; + fl6.flowi6_uid = sock_net_uid(net, sk); + fl6.flowlabel = ip6_flowinfo(iph6); + fl6.flowi6_proto = iph6->nexthdr; + fl6.daddr = iph6->daddr; + fl6.saddr = iph6->saddr; + + err = ipv6_stub->ipv6_dst_lookup(net, skb->sk, &dst, &fl6); + if (err || IS_ERR(dst)) + return -EINVAL; + } + if (unlikely(dst->error)) { + dst_release(dst); + return -EINVAL; + } + + /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it + * was done for the previous dst, so we are doing it here again, in + * case the new dst needs much more space. The call below is a noop + * if there is enough header space in skb. + */ + err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev)); + if (unlikely(err)) + return err; + + skb_dst_drop(skb); + skb_dst_set(skb, dst); + + err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb); + if (unlikely(err)) + return err; + + /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */ + return LWTUNNEL_XMIT_DONE; +} + static int bpf_xmit(struct sk_buff *skb) { struct dst_entry *dst = skb_dst(skb); @@ -155,11 +266,20 @@ static int bpf_xmit(struct sk_buff *skb) bpf = bpf_lwt_lwtunnel(dst->lwtstate); if (bpf->xmit.prog) { + __be16 proto = skb->protocol; int ret; ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT); switch (ret) { case BPF_OK: + /* If the header changed, e.g. via bpf_lwt_push_encap, + * BPF_LWT_REROUTE below should have been used if the + * protocol was also changed. + */ + if (skb->protocol != proto) { + kfree_skb(skb); + return -EINVAL; + } /* If the header was expanded, headroom might be too * small for L2 header to come, expand as needed. */ @@ -170,6 +290,8 @@ static int bpf_xmit(struct sk_buff *skb) return LWTUNNEL_XMIT_CONTINUE; case BPF_REDIRECT: return LWTUNNEL_XMIT_DONE; + case BPF_LWT_REROUTE: + return bpf_lwt_xmit_reroute(skb); default: return ret; } -- cgit