| Message ID | 20230613-so-reuseport-v3-6-907b4cbb7b99@isovalent.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add SO_REUSEPORT support for TC bpf_sk_assign | expand |
From: Lorenz Bauer <lmb@isovalent.com> Date: Mon, 26 Jun 2023 16:09:03 +0100 > Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT > sockets. This means we can't use the helper to steer traffic to Envoy, > which configures SO_REUSEPORT on its sockets. In turn, we're blocked > from removing TPROXY from our setup. > > The reason that bpf_sk_assign refuses such sockets is that the > bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, > one of the reuseport sockets is selected by hash. This could cause > dispatch to the "wrong" socket: > > sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash > bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed > > Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup > helpers unfortunately. In the tc context, L2 headers are at the start > of the skb, while SK_REUSEPORT expects L3 headers instead. > > Instead, we execute the SK_REUSEPORT program when the assigned socket > is pulled out of the skb, further up the stack. This creates some > trickiness with regards to refcounting as bpf_sk_assign will put both > refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU > freed. We can infer that the sk_assigned socket is RCU freed if the > reuseport lookup succeeds, but convincing yourself of this fact isn't > straight forward. Therefore we defensively check refcounting on the > sk_assign sock even though it's probably not required in practice. > > Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") > Fixes: cf7fbe660f2d ("bpf: Add socket assign support") > Co-developed-by: Daniel Borkmann <daniel@iogearbox.net> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> > Signed-off-by: Lorenz Bauer <lmb@isovalent.com> > Cc: Joe Stringer <joe@cilium.io> > Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ > --- > include/net/inet6_hashtables.h | 59 ++++++++++++++++++++++++++++++++++++++---- > include/net/inet_hashtables.h | 52 +++++++++++++++++++++++++++++++++++-- > include/net/sock.h | 7 +++-- > include/uapi/linux/bpf.h | 3 --- > net/core/filter.c | 2 -- > net/ipv4/udp.c | 8 ++++-- > net/ipv6/udp.c | 10 ++++--- > tools/include/uapi/linux/bpf.h | 3 --- > 8 files changed, 122 insertions(+), 22 deletions(-) > > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h > index 4d2a1a3c0be7..4d300af6ccb6 100644 > --- a/include/net/inet6_hashtables.h > +++ b/include/net/inet6_hashtables.h > @@ -103,6 +103,49 @@ static inline struct sock *__inet6_lookup(struct net *net, > daddr, hnum, dif, sdif); > } > > +static inline > +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, > + const struct in6_addr *saddr, const __be16 sport, > + const struct in6_addr *daddr, const __be16 dport, > + bool *refcounted, inet6_ehashfn_t ehashfn) > +{ > + struct sock *sk, *reuse_sk; > + bool prefetched; > + > + sk = skb_steal_sock(skb, refcounted, &prefetched); > + if (!sk) > + return NULL; > + > + if (!prefetched) > + return sk; > + > + if (sk->sk_protocol == IPPROTO_TCP) { > + if (sk->sk_state != TCP_LISTEN) > + return sk; > + } else if (sk->sk_protocol == IPPROTO_UDP) { > + if (sk->sk_state != TCP_CLOSE) > + return sk; > + } else { > + return sk; > + } > + > + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, > + saddr, sport, daddr, ntohs(dport), > + ehashfn); > + if (!reuse_sk || reuse_sk == sk) > + return sk; > + > + /* We've chosen a new reuseport sock which is never refcounted. > + * sk might be refcounted however, drop the reference if necessary. > + */ > + if (*refcounted) { > + sock_put(sk); > + *refcounted = false; > + } As *refcounted should be false here (TCP_LISTEN and UDP sk have SOCK_RCU_FREE and other sk does not reach here), I prefer adding WARN_ON_ONCE() to catch a future bug: WARN_ON_ONCE(*refcounted); sock_put(sk); > + > + return reuse_sk; > +} > + > static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, > struct sk_buff *skb, int doff, > const __be16 sport, > @@ -110,14 +153,20 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, > int iif, int sdif, > bool *refcounted) > { > - struct sock *sk = skb_steal_sock(skb, refcounted); > - > + struct net *net = dev_net(skb_dst(skb)->dev); > + const struct ipv6hdr *ip6h = ipv6_hdr(skb); > + struct sock *sk; > + > + sk = inet6_steal_sock(net, skb, doff, &ip6h->saddr, sport, &ip6h->daddr, dport, > + refcounted, inet6_ehashfn); > + if (IS_ERR(sk)) > + return NULL; > if (sk) > return sk; > > - return __inet6_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, > - doff, &ipv6_hdr(skb)->saddr, sport, > - &ipv6_hdr(skb)->daddr, ntohs(dport), > + return __inet6_lookup(net, hashinfo, skb, > + doff, &ip6h->saddr, sport, > + &ip6h->daddr, ntohs(dport), > iif, sdif, refcounted); > } > > diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h > index aa02f1db1f86..2c405d9df300 100644 > --- a/include/net/inet_hashtables.h > +++ b/include/net/inet_hashtables.h > @@ -449,6 +449,49 @@ static inline struct sock *inet_lookup(struct net *net, > return sk; > } > > +static inline > +struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff, > + const __be32 saddr, const __be16 sport, > + const __be32 daddr, const __be16 dport, > + bool *refcounted, inet_ehashfn_t ehashfn) > +{ > + struct sock *sk, *reuse_sk; > + bool prefetched; > + > + sk = skb_steal_sock(skb, refcounted, &prefetched); > + if (!sk) > + return NULL; > + > + if (!prefetched) > + return sk; > + > + if (sk->sk_protocol == IPPROTO_TCP) { > + if (sk->sk_state != TCP_LISTEN) > + return sk; > + } else if (sk->sk_protocol == IPPROTO_UDP) { > + if (sk->sk_state != TCP_CLOSE) > + return sk; > + } else { > + return sk; > + } > + > + reuse_sk = inet_lookup_reuseport(net, sk, skb, doff, > + saddr, sport, daddr, ntohs(dport), > + ehashfn); > + if (!reuse_sk || reuse_sk == sk) > + return sk; > + > + /* We've chosen a new reuseport sock which is never refcounted. > + * sk might be refcounted however, drop the reference if necessary. > + */ > + if (*refcounted) { > + sock_put(sk); > + *refcounted = false; > + } > + > + return reuse_sk; > +} > + > static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, > struct sk_buff *skb, > int doff, > @@ -457,13 +500,18 @@ static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, > const int sdif, > bool *refcounted) > { > - struct sock *sk = skb_steal_sock(skb, refcounted); > + struct net *net = dev_net(skb_dst(skb)->dev); > const struct iphdr *iph = ip_hdr(skb); > + struct sock *sk; > > + sk = inet_steal_sock(net, skb, doff, iph->saddr, sport, iph->daddr, dport, > + refcounted, inet_ehashfn); > + if (IS_ERR(sk)) > + return NULL; > if (sk) > return sk; > > - return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, > + return __inet_lookup(net, hashinfo, skb, > doff, iph->saddr, sport, > iph->daddr, dport, inet_iif(skb), sdif, > refcounted); > diff --git a/include/net/sock.h b/include/net/sock.h > index 656ea89f60ff..5645570c2a64 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -2806,20 +2806,23 @@ sk_is_refcounted(struct sock *sk) > * skb_steal_sock - steal a socket from an sk_buff > * @skb: sk_buff to steal the socket from > * @refcounted: is set to true if the socket is reference-counted > + * @prefetched: is set to true if the socket was assigned from bpf > */ > static inline struct sock * > -skb_steal_sock(struct sk_buff *skb, bool *refcounted) > +skb_steal_sock(struct sk_buff *skb, bool *refcounted, bool *prefetched) > { > if (skb->sk) { > struct sock *sk = skb->sk; > > *refcounted = true; > - if (skb_sk_is_prefetched(skb)) > + *prefetched = skb_sk_is_prefetched(skb); > + if (*prefetched) > *refcounted = sk_is_refcounted(sk); > skb->destructor = NULL; > skb->sk = NULL; > return sk; > } > + *prefetched = false; > *refcounted = false; > return NULL; > } > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index a7b5e91dd768..d6fb6f43b0f3 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -4158,9 +4158,6 @@ union bpf_attr { > * **-EOPNOTSUPP** if the operation is not supported, for example > * a call from outside of TC ingress. > * > - * **-ESOCKTNOSUPPORT** if the socket type is not supported > - * (reuseport). > - * > * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) > * Description > * Helper is overloaded depending on BPF program type. This > diff --git a/net/core/filter.c b/net/core/filter.c > index 428df050d021..d4be0a1d754c 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -7278,8 +7278,6 @@ BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) > return -EOPNOTSUPP; > if (unlikely(dev_net(skb->dev) != sock_net(sk))) > return -ENETUNREACH; > - if (unlikely(sk_fullsock(sk) && sk->sk_reuseport)) > - return -ESOCKTNOSUPPORT; > if (sk_is_refcounted(sk) && > unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) > return -ENOENT; > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index eb79268f216d..b256f1f73b4d 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -2388,7 +2388,11 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > if (udp4_csum_init(skb, uh, proto)) > goto csum_error; > > - sk = skb_steal_sock(skb, &refcounted); > + sk = inet_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, > + &refcounted, udp_ehashfn); > + if (IS_ERR(sk)) > + goto no_sk; > + > if (sk) { > struct dst_entry *dst = skb_dst(skb); > int ret; > @@ -2409,7 +2413,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable); > if (sk) > return udp_unicast_rcv_skb(sk, skb, uh); > - > +no_sk: > if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) > goto drop; > nf_reset_ct(skb); > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c > index 8a6d94cabee0..2d4c05bc322a 100644 > --- a/net/ipv6/udp.c > +++ b/net/ipv6/udp.c > @@ -923,9 +923,9 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; > const struct in6_addr *saddr, *daddr; > struct net *net = dev_net(skb->dev); > + bool refcounted; > struct udphdr *uh; > struct sock *sk; > - bool refcounted; > u32 ulen = 0; > > if (!pskb_may_pull(skb, sizeof(struct udphdr))) > @@ -962,7 +962,11 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > goto csum_error; > > /* Check if the socket is already available, e.g. due to early demux */ > - sk = skb_steal_sock(skb, &refcounted); > + sk = inet6_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, > + &refcounted, udp6_ehashfn); > + if (IS_ERR(sk)) > + goto no_sk; > + > if (sk) { > struct dst_entry *dst = skb_dst(skb); > int ret; > @@ -996,7 +1000,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, > goto report_csum_error; > return udp6_unicast_rcv_skb(sk, skb, uh); > } > - > +no_sk: > reason = SKB_DROP_REASON_NO_SOCKET; > > if (!uh->check) > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > index a7b5e91dd768..d6fb6f43b0f3 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -4158,9 +4158,6 @@ union bpf_attr { > * **-EOPNOTSUPP** if the operation is not supported, for example > * a call from outside of TC ingress. > * > - * **-ESOCKTNOSUPPORT** if the socket type is not supported > - * (reuseport). > - * > * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) > * Description > * Helper is overloaded depending on BPF program type. This > > -- > 2.40.1
From: Kuniyuki Iwashima <kuniyu@amazon.com> Date: Mon, 26 Jun 2023 14:08:46 -0700 > From: Lorenz Bauer <lmb@isovalent.com> > Date: Mon, 26 Jun 2023 16:09:03 +0100 > > Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT > > sockets. This means we can't use the helper to steer traffic to Envoy, > > which configures SO_REUSEPORT on its sockets. In turn, we're blocked > > from removing TPROXY from our setup. > > > > The reason that bpf_sk_assign refuses such sockets is that the > > bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, > > one of the reuseport sockets is selected by hash. This could cause > > dispatch to the "wrong" socket: > > > > sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash > > bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed > > > > Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup > > helpers unfortunately. In the tc context, L2 headers are at the start > > of the skb, while SK_REUSEPORT expects L3 headers instead. > > > > Instead, we execute the SK_REUSEPORT program when the assigned socket > > is pulled out of the skb, further up the stack. This creates some > > trickiness with regards to refcounting as bpf_sk_assign will put both > > refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU > > freed. We can infer that the sk_assigned socket is RCU freed if the > > reuseport lookup succeeds, but convincing yourself of this fact isn't > > straight forward. Therefore we defensively check refcounting on the > > sk_assign sock even though it's probably not required in practice. > > > > Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") > > Fixes: cf7fbe660f2d ("bpf: Add socket assign support") > > Co-developed-by: Daniel Borkmann <daniel@iogearbox.net> > > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> > > Signed-off-by: Lorenz Bauer <lmb@isovalent.com> > > Cc: Joe Stringer <joe@cilium.io> > > Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ > > --- > > include/net/inet6_hashtables.h | 59 ++++++++++++++++++++++++++++++++++++++---- > > include/net/inet_hashtables.h | 52 +++++++++++++++++++++++++++++++++++-- > > include/net/sock.h | 7 +++-- > > include/uapi/linux/bpf.h | 3 --- > > net/core/filter.c | 2 -- > > net/ipv4/udp.c | 8 ++++-- > > net/ipv6/udp.c | 10 ++++--- > > tools/include/uapi/linux/bpf.h | 3 --- > > 8 files changed, 122 insertions(+), 22 deletions(-) > > > > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h > > index 4d2a1a3c0be7..4d300af6ccb6 100644 > > --- a/include/net/inet6_hashtables.h > > +++ b/include/net/inet6_hashtables.h > > @@ -103,6 +103,49 @@ static inline struct sock *__inet6_lookup(struct net *net, > > daddr, hnum, dif, sdif); > > } > > > > +static inline > > +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, > > + const struct in6_addr *saddr, const __be16 sport, > > + const struct in6_addr *daddr, const __be16 dport, > > + bool *refcounted, inet6_ehashfn_t ehashfn) > > +{ > > + struct sock *sk, *reuse_sk; > > + bool prefetched; > > + > > + sk = skb_steal_sock(skb, refcounted, &prefetched); > > + if (!sk) > > + return NULL; > > + > > + if (!prefetched) > > + return sk; > > + > > + if (sk->sk_protocol == IPPROTO_TCP) { > > + if (sk->sk_state != TCP_LISTEN) > > + return sk; > > + } else if (sk->sk_protocol == IPPROTO_UDP) { > > + if (sk->sk_state != TCP_CLOSE) > > + return sk; > > + } else { > > + return sk; > > + } > > + > > + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, > > + saddr, sport, daddr, ntohs(dport), > > + ehashfn); > > + if (!reuse_sk || reuse_sk == sk) > > + return sk; > > + > > + /* We've chosen a new reuseport sock which is never refcounted. > > + * sk might be refcounted however, drop the reference if necessary. > > + */ > > + if (*refcounted) { > > + sock_put(sk); > > + *refcounted = false; > > + } > > As *refcounted should be false here (TCP_LISTEN and UDP sk have > SOCK_RCU_FREE and other sk does not reach here), I prefer adding > WARN_ON_ONCE() to catch a future bug: > > WARN_ON_ONCE(*refcounted); > sock_put(sk); Sorry, sock_put(sk) is not needed here.
diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h index 4d2a1a3c0be7..4d300af6ccb6 100644 --- a/include/net/inet6_hashtables.h +++ b/include/net/inet6_hashtables.h @@ -103,6 +103,49 @@ static inline struct sock *__inet6_lookup(struct net *net, daddr, hnum, dif, sdif); } +static inline +struct sock *inet6_steal_sock(struct net *net, struct sk_buff *skb, int doff, + const struct in6_addr *saddr, const __be16 sport, + const struct in6_addr *daddr, const __be16 dport, + bool *refcounted, inet6_ehashfn_t ehashfn) +{ + struct sock *sk, *reuse_sk; + bool prefetched; + + sk = skb_steal_sock(skb, refcounted, &prefetched); + if (!sk) + return NULL; + + if (!prefetched) + return sk; + + if (sk->sk_protocol == IPPROTO_TCP) { + if (sk->sk_state != TCP_LISTEN) + return sk; + } else if (sk->sk_protocol == IPPROTO_UDP) { + if (sk->sk_state != TCP_CLOSE) + return sk; + } else { + return sk; + } + + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, + saddr, sport, daddr, ntohs(dport), + ehashfn); + if (!reuse_sk || reuse_sk == sk) + return sk; + + /* We've chosen a new reuseport sock which is never refcounted. + * sk might be refcounted however, drop the reference if necessary. + */ + if (*refcounted) { + sock_put(sk); + *refcounted = false; + } + + return reuse_sk; +} + static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, struct sk_buff *skb, int doff, const __be16 sport, @@ -110,14 +153,20 @@ static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo, int iif, int sdif, bool *refcounted) { - struct sock *sk = skb_steal_sock(skb, refcounted); - + struct net *net = dev_net(skb_dst(skb)->dev); + const struct ipv6hdr *ip6h = ipv6_hdr(skb); + struct sock *sk; + + sk = inet6_steal_sock(net, skb, doff, &ip6h->saddr, sport, &ip6h->daddr, dport, + refcounted, inet6_ehashfn); + if (IS_ERR(sk)) + return NULL; if (sk) return sk; - return __inet6_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, - doff, &ipv6_hdr(skb)->saddr, sport, - &ipv6_hdr(skb)->daddr, ntohs(dport), + return __inet6_lookup(net, hashinfo, skb, + doff, &ip6h->saddr, sport, + &ip6h->daddr, ntohs(dport), iif, sdif, refcounted); } diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h index aa02f1db1f86..2c405d9df300 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -449,6 +449,49 @@ static inline struct sock *inet_lookup(struct net *net, return sk; } +static inline +struct sock *inet_steal_sock(struct net *net, struct sk_buff *skb, int doff, + const __be32 saddr, const __be16 sport, + const __be32 daddr, const __be16 dport, + bool *refcounted, inet_ehashfn_t ehashfn) +{ + struct sock *sk, *reuse_sk; + bool prefetched; + + sk = skb_steal_sock(skb, refcounted, &prefetched); + if (!sk) + return NULL; + + if (!prefetched) + return sk; + + if (sk->sk_protocol == IPPROTO_TCP) { + if (sk->sk_state != TCP_LISTEN) + return sk; + } else if (sk->sk_protocol == IPPROTO_UDP) { + if (sk->sk_state != TCP_CLOSE) + return sk; + } else { + return sk; + } + + reuse_sk = inet_lookup_reuseport(net, sk, skb, doff, + saddr, sport, daddr, ntohs(dport), + ehashfn); + if (!reuse_sk || reuse_sk == sk) + return sk; + + /* We've chosen a new reuseport sock which is never refcounted. + * sk might be refcounted however, drop the reference if necessary. + */ + if (*refcounted) { + sock_put(sk); + *refcounted = false; + } + + return reuse_sk; +} + static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, struct sk_buff *skb, int doff, @@ -457,13 +500,18 @@ static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, const int sdif, bool *refcounted) { - struct sock *sk = skb_steal_sock(skb, refcounted); + struct net *net = dev_net(skb_dst(skb)->dev); const struct iphdr *iph = ip_hdr(skb); + struct sock *sk; + sk = inet_steal_sock(net, skb, doff, iph->saddr, sport, iph->daddr, dport, + refcounted, inet_ehashfn); + if (IS_ERR(sk)) + return NULL; if (sk) return sk; - return __inet_lookup(dev_net(skb_dst(skb)->dev), hashinfo, skb, + return __inet_lookup(net, hashinfo, skb, doff, iph->saddr, sport, iph->daddr, dport, inet_iif(skb), sdif, refcounted); diff --git a/include/net/sock.h b/include/net/sock.h index 656ea89f60ff..5645570c2a64 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2806,20 +2806,23 @@ sk_is_refcounted(struct sock *sk) * skb_steal_sock - steal a socket from an sk_buff * @skb: sk_buff to steal the socket from * @refcounted: is set to true if the socket is reference-counted + * @prefetched: is set to true if the socket was assigned from bpf */ static inline struct sock * -skb_steal_sock(struct sk_buff *skb, bool *refcounted) +skb_steal_sock(struct sk_buff *skb, bool *refcounted, bool *prefetched) { if (skb->sk) { struct sock *sk = skb->sk; *refcounted = true; - if (skb_sk_is_prefetched(skb)) + *prefetched = skb_sk_is_prefetched(skb); + if (*prefetched) *refcounted = sk_is_refcounted(sk); skb->destructor = NULL; skb->sk = NULL; return sk; } + *prefetched = false; *refcounted = false; return NULL; } diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index a7b5e91dd768..d6fb6f43b0f3 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -4158,9 +4158,6 @@ union bpf_attr { * **-EOPNOTSUPP** if the operation is not supported, for example * a call from outside of TC ingress. * - * **-ESOCKTNOSUPPORT** if the socket type is not supported - * (reuseport). - * * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) * Description * Helper is overloaded depending on BPF program type. This diff --git a/net/core/filter.c b/net/core/filter.c index 428df050d021..d4be0a1d754c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7278,8 +7278,6 @@ BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) return -EOPNOTSUPP; if (unlikely(dev_net(skb->dev) != sock_net(sk))) return -ENETUNREACH; - if (unlikely(sk_fullsock(sk) && sk->sk_reuseport)) - return -ESOCKTNOSUPPORT; if (sk_is_refcounted(sk) && unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) return -ENOENT; diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index eb79268f216d..b256f1f73b4d 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -2388,7 +2388,11 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, if (udp4_csum_init(skb, uh, proto)) goto csum_error; - sk = skb_steal_sock(skb, &refcounted); + sk = inet_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, + &refcounted, udp_ehashfn); + if (IS_ERR(sk)) + goto no_sk; + if (sk) { struct dst_entry *dst = skb_dst(skb); int ret; @@ -2409,7 +2413,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable); if (sk) return udp_unicast_rcv_skb(sk, skb, uh); - +no_sk: if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) goto drop; nf_reset_ct(skb); diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 8a6d94cabee0..2d4c05bc322a 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -923,9 +923,9 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; const struct in6_addr *saddr, *daddr; struct net *net = dev_net(skb->dev); + bool refcounted; struct udphdr *uh; struct sock *sk; - bool refcounted; u32 ulen = 0; if (!pskb_may_pull(skb, sizeof(struct udphdr))) @@ -962,7 +962,11 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, goto csum_error; /* Check if the socket is already available, e.g. due to early demux */ - sk = skb_steal_sock(skb, &refcounted); + sk = inet6_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest, + &refcounted, udp6_ehashfn); + if (IS_ERR(sk)) + goto no_sk; + if (sk) { struct dst_entry *dst = skb_dst(skb); int ret; @@ -996,7 +1000,7 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable, goto report_csum_error; return udp6_unicast_rcv_skb(sk, skb, uh); } - +no_sk: reason = SKB_DROP_REASON_NO_SOCKET; if (!uh->check) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index a7b5e91dd768..d6fb6f43b0f3 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -4158,9 +4158,6 @@ union bpf_attr { * **-EOPNOTSUPP** if the operation is not supported, for example * a call from outside of TC ingress. * - * **-ESOCKTNOSUPPORT** if the socket type is not supported - * (reuseport). - * * long bpf_sk_assign(struct bpf_sk_lookup *ctx, struct bpf_sock *sk, u64 flags) * Description * Helper is overloaded depending on BPF program type. This
Currently the bpf_sk_assign helper in tc BPF context refuses SO_REUSEPORT sockets. This means we can't use the helper to steer traffic to Envoy, which configures SO_REUSEPORT on its sockets. In turn, we're blocked from removing TPROXY from our setup. The reason that bpf_sk_assign refuses such sockets is that the bpf_sk_lookup helpers don't execute SK_REUSEPORT programs. Instead, one of the reuseport sockets is selected by hash. This could cause dispatch to the "wrong" socket: sk = bpf_sk_lookup_tcp(...) // select SO_REUSEPORT by hash bpf_sk_assign(skb, sk) // SK_REUSEPORT wasn't executed Fixing this isn't as simple as invoking SK_REUSEPORT from the lookup helpers unfortunately. In the tc context, L2 headers are at the start of the skb, while SK_REUSEPORT expects L3 headers instead. Instead, we execute the SK_REUSEPORT program when the assigned socket is pulled out of the skb, further up the stack. This creates some trickiness with regards to refcounting as bpf_sk_assign will put both refcounted and RCU freed sockets in skb->sk. reuseport sockets are RCU freed. We can infer that the sk_assigned socket is RCU freed if the reuseport lookup succeeds, but convincing yourself of this fact isn't straight forward. Therefore we defensively check refcounting on the sk_assign sock even though it's probably not required in practice. Fixes: 8e368dc72e86 ("bpf: Fix use of sk->sk_reuseport from sk_assign") Fixes: cf7fbe660f2d ("bpf: Add socket assign support") Co-developed-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Lorenz Bauer <lmb@isovalent.com> Cc: Joe Stringer <joe@cilium.io> Link: https://lore.kernel.org/bpf/CACAyw98+qycmpQzKupquhkxbvWK4OFyDuuLMBNROnfWMZxUWeA@mail.gmail.com/ --- include/net/inet6_hashtables.h | 59 ++++++++++++++++++++++++++++++++++++++---- include/net/inet_hashtables.h | 52 +++++++++++++++++++++++++++++++++++-- include/net/sock.h | 7 +++-- include/uapi/linux/bpf.h | 3 --- net/core/filter.c | 2 -- net/ipv4/udp.c | 8 ++++-- net/ipv6/udp.c | 10 ++++--- tools/include/uapi/linux/bpf.h | 3 --- 8 files changed, 122 insertions(+), 22 deletions(-)