| Message ID | 20230613-so-reuseport-v4-6-4ece76708bba@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: Wed, 28 Jun 2023 10:48:21 +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/ Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> I left minor comments below, but this series overall looks good. Thanks! > --- > include/net/inet6_hashtables.h | 56 ++++++++++++++++++++++++++++++++++++++---- > include/net/inet_hashtables.h | 49 ++++++++++++++++++++++++++++++++++-- > 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, 116 insertions(+), 22 deletions(-) > > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h > index a6722d6ef80f..7d677b89f269 100644 > --- a/include/net/inet6_hashtables.h > +++ b/include/net/inet6_hashtables.h > @@ -103,6 +103,46 @@ 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) nit: compiler might have optimised though, given here is the fast path, we can save reuse_sk == sk check. > + return sk; > + > + /* We've chosen a new reuseport sock which is never refcounted. This > + * implies that sk also isn't refcounted. > + */ > + WARN_ON_ONCE(*refcounted); > + > + 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 +150,20 @@ 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 c0532cc7587f..c6ae0af12ce0 100644 > --- a/include/net/inet_hashtables.h > +++ b/include/net/inet_hashtables.h > @@ -449,6 +449,46 @@ 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) Same here. > + return sk; > + > + /* We've chosen a new reuseport sock which is never refcounted. This > + * implies that sk also isn't refcounted. > + */ > + WARN_ON_ONCE(*refcounted); > + > + return reuse_sk; > +} > + > static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, > struct sk_buff *skb, > int doff, > @@ -457,13 +497,18 @@ 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: Lorenz Bauer <lmb@isovalent.com> Date: Wed, 28 Jun 2023 10:48:21 +0100 > diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h > index a6722d6ef80f..7d677b89f269 100644 > --- a/include/net/inet6_hashtables.h > +++ b/include/net/inet6_hashtables.h > @@ -103,6 +103,46 @@ 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. This > + * implies that sk also isn't refcounted. > + */ > + WARN_ON_ONCE(*refcounted); One more nit. WARN_ON_ONCE() should be tested before inet6?_lookup_reuseport() not to miss the !reuse_sk case. > + > + return reuse_sk; > +}
On Wed, Jun 28, 2023 at 7:50 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > + } else { > > + return sk; > > + } > > + > > + reuse_sk = inet6_lookup_reuseport(net, sk, skb, doff, > > + saddr, sport, daddr, ntohs(dport), > > + ehashfn); > > + if (!reuse_sk || reuse_sk == sk) > > nit: compiler might have optimised though, given here is the fast path, > we can save reuse_sk == sk check. Ack.
On Wed, Jun 28, 2023 at 7:54 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > + 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. This > > + * implies that sk also isn't refcounted. > > + */ > > + WARN_ON_ONCE(*refcounted); > > One more nit. > > WARN_ON_ONCE() should be tested before inet6?_lookup_reuseport() not to > miss the !reuse_sk case. I was just pondering that as well, but I came to the opposite conclusion. In the !reuse_sk case we don't really know anything about sk, except that it isn't part of a reuseport group. How can we be sure that it's not refcounted?
From: Lorenz Bauer <lmb@isovalent.com> Date: Mon, 3 Jul 2023 10:57:23 +0100 > On Wed, Jun 28, 2023 at 7:54 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > > > + 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. This > > > + * implies that sk also isn't refcounted. > > > + */ > > > + WARN_ON_ONCE(*refcounted); > > > > One more nit. > > > > WARN_ON_ONCE() should be tested before inet6?_lookup_reuseport() not to > > miss the !reuse_sk case. > > I was just pondering that as well, but I came to the opposite > conclusion. In the !reuse_sk case we don't really know anything about > sk, except that it isn't part of a reuseport group. How can we be sure > that it's not refcounted? Sorry for late reply. What we know about sk before inet6?_lookup_reuseport() are (1) sk was full socket in bpf_sk_assign() (2) sk had SOCK_RCU_FREE in bpf_sk_assign() (3) sk was TCP_LISTEN here if TCP After bpf_sk_assign(), reqsk is never converted to fullsock, and UDP never clears SOCK_RCU_FREE. If sk is TCP, now we are in the RCU grace period and confirmed sk->sk_state was TCP_LISTEN. Then, TCP_LISTEN sk cannot be reused and SOCK_RCU_FREE is never cleared. So, before/after inet6?_lookup_reuseport(), the fact that sk is not refcounted here should not change in spite of that reuse_sk is NULL. What do you think ?
On Thu, Jul 6, 2023 at 1:41 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > Sorry for late reply. > > What we know about sk before inet6?_lookup_reuseport() are > > (1) sk was full socket in bpf_sk_assign() > (2) sk had SOCK_RCU_FREE in bpf_sk_assign() > (3) sk was TCP_LISTEN here if TCP Are we looking at the same bpf_sk_assign? Confusingly there are two very similarly named functions. The one we care about is: BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) { if (!sk || flags != 0) return -EINVAL; if (!skb_at_tc_ingress(skb)) return -EOPNOTSUPP; if (unlikely(dev_net(skb->dev) != sock_net(sk))) return -ENETUNREACH; if (sk_is_refcounted(sk) && unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) return -ENOENT; skb_orphan(skb); skb->sk = sk; skb->destructor = sock_pfree; return 0; } From this we can't tell what state the socket is in or whether it is RCU freed or not. Thanks Lorenz
From: Lorenz Bauer <lmb@isovalent.com> Date: Thu, 6 Jul 2023 09:11:15 +0100 > On Thu, Jul 6, 2023 at 1:41 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > > > Sorry for late reply. > > > > What we know about sk before inet6?_lookup_reuseport() are > > > > (1) sk was full socket in bpf_sk_assign() > > (2) sk had SOCK_RCU_FREE in bpf_sk_assign() > > (3) sk was TCP_LISTEN here if TCP > > Are we looking at the same bpf_sk_assign? Confusingly there are two > very similarly named functions. The one we care about is: > > BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) > { > if (!sk || flags != 0) > return -EINVAL; > if (!skb_at_tc_ingress(skb)) > return -EOPNOTSUPP; > if (unlikely(dev_net(skb->dev) != sock_net(sk))) > return -ENETUNREACH; > if (sk_is_refcounted(sk) && > unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) > return -ENOENT; > > skb_orphan(skb); > skb->sk = sk; > skb->destructor = sock_pfree; > > return 0; > } > > From this we can't tell what state the socket is in or whether it is > RCU freed or not. But we can in inet6?_steal_sock() by calling sk_is_refcounted() again via skb_steal_sock(). In inet6?_steal_sock(), we call inet6?_lookup_reuseport() only for sk that was a TCP listener or UDP non-connected socket until just before the sk_state checks. Then, we know *refcounted should be false for such sockets even before inet6?_lookup_reuseport(). After the checks, sk might be poped out of the reuseport group before inet6?_lookup_reuseport() and reuse_sk might be NULL, but it's not related because *refcounted is a value for sk, not for reuse_sk.
On Thu, Jul 6, 2023 at 8:33 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > From: Lorenz Bauer <lmb@isovalent.com> > Date: Thu, 6 Jul 2023 09:11:15 +0100 > > On Thu, Jul 6, 2023 at 1:41 AM Kuniyuki Iwashima <kuniyu@amazon.com> wrote: > > > > > > Sorry for late reply. > > > > > > What we know about sk before inet6?_lookup_reuseport() are > > > > > > (1) sk was full socket in bpf_sk_assign() > > > (2) sk had SOCK_RCU_FREE in bpf_sk_assign() > > > (3) sk was TCP_LISTEN here if TCP > > > > Are we looking at the same bpf_sk_assign? Confusingly there are two > > very similarly named functions. The one we care about is: > > > > BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) > > { > > if (!sk || flags != 0) > > return -EINVAL; > > if (!skb_at_tc_ingress(skb)) > > return -EOPNOTSUPP; > > if (unlikely(dev_net(skb->dev) != sock_net(sk))) > > return -ENETUNREACH; > > if (sk_is_refcounted(sk) && > > unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) > > return -ENOENT; > > > > skb_orphan(skb); > > skb->sk = sk; > > skb->destructor = sock_pfree; > > > > return 0; > > } > > > > From this we can't tell what state the socket is in or whether it is > > RCU freed or not. > > But we can in inet6?_steal_sock() by calling sk_is_refcounted() again > via skb_steal_sock(). > > In inet6?_steal_sock(), we call inet6?_lookup_reuseport() only for > sk that was a TCP listener or UDP non-connected socket until just before > the sk_state checks. Then, we know *refcounted should be false for such > sockets even before inet6?_lookup_reuseport(). > > After the checks, sk might be poped out of the reuseport group before > inet6?_lookup_reuseport() and reuse_sk might be NULL, but it's not > related because *refcounted is a value for sk, not for reuse_sk. I was about to apply v5 before I noticed this discussion on v4. Sounds like v6 will be needed. Next time please continue discussion in the latest version.
diff --git a/include/net/inet6_hashtables.h b/include/net/inet6_hashtables.h index a6722d6ef80f..7d677b89f269 100644 --- a/include/net/inet6_hashtables.h +++ b/include/net/inet6_hashtables.h @@ -103,6 +103,46 @@ 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. This + * implies that sk also isn't refcounted. + */ + WARN_ON_ONCE(*refcounted); + + 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 +150,20 @@ 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 c0532cc7587f..c6ae0af12ce0 100644 --- a/include/net/inet_hashtables.h +++ b/include/net/inet_hashtables.h @@ -449,6 +449,46 @@ 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. This + * implies that sk also isn't refcounted. + */ + WARN_ON_ONCE(*refcounted); + + return reuse_sk; +} + static inline struct sock *__inet_lookup_skb(struct inet_hashinfo *hashinfo, struct sk_buff *skb, int doff, @@ -457,13 +497,18 @@ 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 | 56 ++++++++++++++++++++++++++++++++++++++---- include/net/inet_hashtables.h | 49 ++++++++++++++++++++++++++++++++++-- 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, 116 insertions(+), 22 deletions(-)