From: Joe Stringer Date: Sun, 29 Mar 2020 22:53:38 +0000 (-0700) Subject: bpf: Add socket assign support X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449;p=linux.git bpf: Add socket assign support Add support for TPROXY via a new bpf helper, bpf_sk_assign(). This helper requires the BPF program to discover the socket via a call to bpf_sk*_lookup_*(), then pass this socket to the new helper. The helper takes its own reference to the socket in addition to any existing reference that may or may not currently be obtained for the duration of BPF processing. For the destination socket to receive the traffic, the traffic must be routed towards that socket via local route. The simplest example route is below, but in practice you may want to route traffic more narrowly (eg by CIDR): $ ip route add local default dev lo This patch avoids trying to introduce an extra bit into the skb->sk, as that would require more invasive changes to all code interacting with the socket to ensure that the bit is handled correctly, such as all error-handling cases along the path from the helper in BPF through to the orphan path in the input. Instead, we opt to use the destructor variable to switch on the prefetch of the socket. Signed-off-by: Joe Stringer Signed-off-by: Alexei Starovoitov Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20200329225342.16317-2-joe@wand.net.nz --- diff --git a/include/net/sock.h b/include/net/sock.h index b5cca7bae69bb..dc398cee78739 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1659,6 +1659,7 @@ void sock_rfree(struct sk_buff *skb); void sock_efree(struct sk_buff *skb); #ifdef CONFIG_INET void sock_edemux(struct sk_buff *skb); +void sock_pfree(struct sk_buff *skb); #else #define sock_edemux sock_efree #endif @@ -2526,6 +2527,16 @@ void sock_net_set(struct sock *sk, struct net *net) write_pnet(&sk->sk_net, net); } +static inline bool +skb_sk_is_prefetched(struct sk_buff *skb) +{ +#ifdef CONFIG_INET + return skb->destructor == sock_pfree; +#else + return false; +#endif /* CONFIG_INET */ +} + static inline struct sock *skb_steal_sock(struct sk_buff *skb) { if (skb->sk) { diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index f1fbc36f58d32..9f786a5a44ac3 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2983,6 +2983,28 @@ union bpf_attr { * **bpf_get_current_cgroup_id**\ (). * Return * The id is returned or 0 in case the id could not be retrieved. + * + * int bpf_sk_assign(struct sk_buff *skb, struct bpf_sock *sk, u64 flags) + * Description + * Assign the *sk* to the *skb*. When combined with appropriate + * routing configuration to receive the packet towards the socket, + * will cause *skb* to be delivered to the specified socket. + * Subsequent redirection of *skb* via **bpf_redirect**\ (), + * **bpf_clone_redirect**\ () or other methods outside of BPF may + * interfere with successful delivery to the socket. + * + * This operation is only valid from TC ingress path. + * + * The *flags* argument must be zero. + * Return + * 0 on success, or a negative errno in case of failure. + * + * * **-EINVAL** Unsupported flags specified. + * * **-ENOENT** Socket is unavailable for assignment. + * * **-ENETUNREACH** Socket is unreachable (wrong netns). + * * **-EOPNOTSUPP** Unsupported operation, for example a + * call from outside of TC ingress. + * * **-ESOCKTNOSUPPORT** Socket type not supported (reuseport). */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3108,7 +3130,8 @@ union bpf_attr { FN(get_ns_current_pid_tgid), \ FN(xdp_output), \ FN(get_netns_cookie), \ - FN(get_current_ancestor_cgroup_id), + FN(get_current_ancestor_cgroup_id), \ + FN(sk_assign), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/net/core/filter.c b/net/core/filter.c index bb4a196c88096..ac5c1633f8d27 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5918,6 +5918,35 @@ static const struct bpf_func_proto bpf_tcp_gen_syncookie_proto = { .arg5_type = ARG_CONST_SIZE, }; +BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags) +{ + if (flags != 0) + return -EINVAL; + if (!skb_at_tc_ingress(skb)) + return -EOPNOTSUPP; + if (unlikely(dev_net(skb->dev) != sock_net(sk))) + return -ENETUNREACH; + if (unlikely(sk->sk_reuseport)) + return -ESOCKTNOSUPPORT; + if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt))) + return -ENOENT; + + skb_orphan(skb); + skb->sk = sk; + skb->destructor = sock_pfree; + + return 0; +} + +static const struct bpf_func_proto bpf_sk_assign_proto = { + .func = bpf_sk_assign, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_PTR_TO_SOCK_COMMON, + .arg3_type = ARG_ANYTHING, +}; + #endif /* CONFIG_INET */ bool bpf_helper_changes_pkt_data(void *func) @@ -6249,6 +6278,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_skb_ecn_set_ce_proto; case BPF_FUNC_tcp_gen_syncookie: return &bpf_tcp_gen_syncookie_proto; + case BPF_FUNC_sk_assign: + return &bpf_sk_assign_proto; #endif default: return bpf_base_func_proto(func_id); diff --git a/net/core/sock.c b/net/core/sock.c index 0fc8937a7ff4c..87e3a03c90563 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2071,6 +2071,17 @@ void sock_efree(struct sk_buff *skb) } EXPORT_SYMBOL(sock_efree); +/* Buffer destructor for prefetch/receive path where reference count may + * not be held, e.g. for listen sockets. + */ +#ifdef CONFIG_INET +void sock_pfree(struct sk_buff *skb) +{ + sock_gen_put(skb->sk); +} +EXPORT_SYMBOL(sock_pfree); +#endif /* CONFIG_INET */ + kuid_t sock_i_uid(struct sock *sk) { kuid_t uid; diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c index aa438c6758a7f..b0c244af1e4d5 100644 --- a/net/ipv4/ip_input.c +++ b/net/ipv4/ip_input.c @@ -509,7 +509,8 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net) IPCB(skb)->iif = skb->skb_iif; /* Must drop socket now because of tproxy. */ - skb_orphan(skb); + if (!skb_sk_is_prefetched(skb)) + skb_orphan(skb); return skb; diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c index 7b089d0ac8cdd..e96304d8a4a7f 100644 --- a/net/ipv6/ip6_input.c +++ b/net/ipv6/ip6_input.c @@ -285,7 +285,8 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev, rcu_read_unlock(); /* Must drop socket now because of tproxy. */ - skb_orphan(skb); + if (!skb_sk_is_prefetched(skb)) + skb_orphan(skb); return skb; err: diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c index 46f47e58b3bea..54d5652cfe6ca 100644 --- a/net/sched/act_bpf.c +++ b/net/sched/act_bpf.c @@ -12,6 +12,7 @@ #include #include +#include #include #include @@ -53,6 +54,8 @@ static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act, bpf_compute_data_pointers(skb); filter_res = BPF_PROG_RUN(filter, skb); } + if (skb_sk_is_prefetched(skb) && filter_res != TC_ACT_OK) + skb_orphan(skb); rcu_read_unlock(); /* A BPF program may overwrite the default action opcode. diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index f1fbc36f58d32..9f786a5a44ac3 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2983,6 +2983,28 @@ union bpf_attr { * **bpf_get_current_cgroup_id**\ (). * Return * The id is returned or 0 in case the id could not be retrieved. + * + * int bpf_sk_assign(struct sk_buff *skb, struct bpf_sock *sk, u64 flags) + * Description + * Assign the *sk* to the *skb*. When combined with appropriate + * routing configuration to receive the packet towards the socket, + * will cause *skb* to be delivered to the specified socket. + * Subsequent redirection of *skb* via **bpf_redirect**\ (), + * **bpf_clone_redirect**\ () or other methods outside of BPF may + * interfere with successful delivery to the socket. + * + * This operation is only valid from TC ingress path. + * + * The *flags* argument must be zero. + * Return + * 0 on success, or a negative errno in case of failure. + * + * * **-EINVAL** Unsupported flags specified. + * * **-ENOENT** Socket is unavailable for assignment. + * * **-ENETUNREACH** Socket is unreachable (wrong netns). + * * **-EOPNOTSUPP** Unsupported operation, for example a + * call from outside of TC ingress. + * * **-ESOCKTNOSUPPORT** Socket type not supported (reuseport). */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3108,7 +3130,8 @@ union bpf_attr { FN(get_ns_current_pid_tgid), \ FN(xdp_output), \ FN(get_netns_cookie), \ - FN(get_current_ancestor_cgroup_id), + FN(get_current_ancestor_cgroup_id), \ + FN(sk_assign), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call