From 8934ce2fd08171e8605f7fada91ee7619fe17ab8 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Wed, 28 Mar 2018 12:49:15 -0700 Subject: bpf: sockmap redirect ingress support Add support for the BPF_F_INGRESS flag in sk_msg redirect helper. To do this add a scatterlist ring for receiving socks to check before calling into regular recvmsg call path. Additionally, because the poll wakeup logic only checked the skb recv queue we need to add a hook in TCP stack (similar to write side) so that we have a way to wake up polling socks when a scatterlist is redirected to that sock. After this all that is needed is for the redirect helper to push the scatterlist into the psock receive queue. Signed-off-by: John Fastabend Signed-off-by: Daniel Borkmann --- net/ipv4/tcp.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 0c31be306572..bccc4c270087 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -485,6 +485,14 @@ static void tcp_tx_timestamp(struct sock *sk, u16 tsflags) } } +static inline bool tcp_stream_is_readable(const struct tcp_sock *tp, + int target, struct sock *sk) +{ + return (tp->rcv_nxt - tp->copied_seq >= target) || + (sk->sk_prot->stream_memory_read ? + sk->sk_prot->stream_memory_read(sk) : false); +} + /* * Wait for a TCP event. * @@ -554,7 +562,7 @@ __poll_t tcp_poll(struct file *file, struct socket *sock, poll_table *wait) tp->urg_data) target++; - if (tp->rcv_nxt - tp->copied_seq >= target) + if (tcp_stream_is_readable(tp, target, sk)) mask |= EPOLLIN | EPOLLRDNORM; if (!(sk->sk_shutdown & SEND_SHUTDOWN)) { -- cgit v1.2.1 From 4fbac77d2d092b475dda9eea66da674369665427 Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Fri, 30 Mar 2018 15:08:02 -0700 Subject: bpf: Hooks for sys_bind == The problem == There is a use-case when all processes inside a cgroup should use one single IP address on a host that has multiple IP configured. Those processes should use the IP for both ingress and egress, for TCP and UDP traffic. So TCP/UDP servers should be bound to that IP to accept incoming connections on it, and TCP/UDP clients should make outgoing connections from that IP. It should not require changing application code since it's often not possible. Currently it's solved by intercepting glibc wrappers around syscalls such as `bind(2)` and `connect(2)`. It's done by a shared library that is preloaded for every process in a cgroup so that whenever TCP/UDP server calls `bind(2)`, the library replaces IP in sockaddr before passing arguments to syscall. When application calls `connect(2)` the library transparently binds the local end of connection to that IP (`bind(2)` with `IP_BIND_ADDRESS_NO_PORT` to avoid performance penalty). Shared library approach is fragile though, e.g.: * some applications clear env vars (incl. `LD_PRELOAD`); * `/etc/ld.so.preload` doesn't help since some applications are linked with option `-z nodefaultlib`; * other applications don't use glibc and there is nothing to intercept. == The solution == The patch provides much more reliable in-kernel solution for the 1st part of the problem: binding TCP/UDP servers on desired IP. It does not depend on application environment and implementation details (whether glibc is used or not). It adds new eBPF program type `BPF_PROG_TYPE_CGROUP_SOCK_ADDR` and attach types `BPF_CGROUP_INET4_BIND` and `BPF_CGROUP_INET6_BIND` (similar to already existing `BPF_CGROUP_INET_SOCK_CREATE`). The new program type is intended to be used with sockets (`struct sock`) in a cgroup and provided by user `struct sockaddr`. Pointers to both of them are parts of the context passed to programs of newly added types. The new attach types provides hooks in `bind(2)` system call for both IPv4 and IPv6 so that one can write a program to override IP addresses and ports user program tries to bind to and apply such a program for whole cgroup. == Implementation notes == [1] Separate attach types for `AF_INET` and `AF_INET6` are added intentionally to prevent reading/writing to offsets that don't make sense for corresponding socket family. E.g. if user passes `sockaddr_in` it doesn't make sense to read from / write to `user_ip6[]` context fields. [2] The write access to `struct bpf_sock_addr_kern` is implemented using special field as an additional "register". There are just two registers in `sock_addr_convert_ctx_access`: `src` with value to write and `dst` with pointer to context that can't be changed not to break later instructions. But the fields, allowed to write to, are not available directly and to access them address of corresponding pointer has to be loaded first. To get additional register the 1st not used by `src` and `dst` one is taken, its content is saved to `bpf_sock_addr_kern.tmp_reg`, then the register is used to load address of pointer field, and finally the register's content is restored from the temporary field after writing `src` value. Signed-off-by: Andrey Ignatov Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- net/ipv4/af_inet.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'net/ipv4') diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index e8c7fad8c329..2dec266507dc 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -450,6 +450,13 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) if (addr_len < sizeof(struct sockaddr_in)) goto out; + /* BPF prog is run before any checks are done so that if the prog + * changes context in a wrong way it will be caught. + */ + err = BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr); + if (err) + goto out; + if (addr->sin_family != AF_INET) { /* Compatibility games : accept AF_UNSPEC (mapped to AF_INET) * only if s_addr is INADDR_ANY. -- cgit v1.2.1 From 3679d585bbc07a1ac4448d5b478b492cad3587ce Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Fri, 30 Mar 2018 15:08:04 -0700 Subject: net: Introduce __inet_bind() and __inet6_bind Refactor `bind()` code to make it ready to be called from BPF helper function `bpf_bind()` (will be added soon). Implementation of `inet_bind()` and `inet6_bind()` is separated into `__inet_bind()` and `__inet6_bind()` correspondingly. These function can be used from both `sk_prot->bind` and `bpf_bind()` contexts. New functions have two additional arguments. `force_bind_address_no_port` forces binding to IP only w/o checking `inet_sock.bind_address_no_port` field. It'll allow to bind local end of a connection to desired IP in `bpf_bind()` w/o changing `bind_address_no_port` field of a socket. It's useful since `bpf_bind()` can return an error and we'd need to restore original value of `bind_address_no_port` in that case if we changed this before calling to the helper. `with_lock` specifies whether to lock socket when working with `struct sk` or not. The argument is set to `true` for `sk_prot->bind`, i.e. old behavior is preserved. But it will be set to `false` for `bpf_bind()` use-case. The reason is all call-sites, where `bpf_bind()` will be called, already hold that socket lock. Signed-off-by: Andrey Ignatov Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- net/ipv4/af_inet.c | 39 ++++++++++++++++++++++++--------------- 1 file changed, 24 insertions(+), 15 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 2dec266507dc..e203a39d6988 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -432,30 +432,37 @@ EXPORT_SYMBOL(inet_release); int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) { - struct sockaddr_in *addr = (struct sockaddr_in *)uaddr; struct sock *sk = sock->sk; - struct inet_sock *inet = inet_sk(sk); - struct net *net = sock_net(sk); - unsigned short snum; - int chk_addr_ret; - u32 tb_id = RT_TABLE_LOCAL; int err; /* If the socket has its own bind function then use it. (RAW) */ if (sk->sk_prot->bind) { - err = sk->sk_prot->bind(sk, uaddr, addr_len); - goto out; + return sk->sk_prot->bind(sk, uaddr, addr_len); } - err = -EINVAL; if (addr_len < sizeof(struct sockaddr_in)) - goto out; + return -EINVAL; /* BPF prog is run before any checks are done so that if the prog * changes context in a wrong way it will be caught. */ err = BPF_CGROUP_RUN_PROG_INET4_BIND(sk, uaddr); if (err) - goto out; + return err; + + return __inet_bind(sk, uaddr, addr_len, false, true); +} +EXPORT_SYMBOL(inet_bind); + +int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len, + bool force_bind_address_no_port, bool with_lock) +{ + struct sockaddr_in *addr = (struct sockaddr_in *)uaddr; + struct inet_sock *inet = inet_sk(sk); + struct net *net = sock_net(sk); + unsigned short snum; + int chk_addr_ret; + u32 tb_id = RT_TABLE_LOCAL; + int err; if (addr->sin_family != AF_INET) { /* Compatibility games : accept AF_UNSPEC (mapped to AF_INET) @@ -499,7 +506,8 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) * would be illegal to use them (multicast/broadcast) in * which case the sending device address is used. */ - lock_sock(sk); + if (with_lock) + lock_sock(sk); /* Check these errors (active socket, double bind). */ err = -EINVAL; @@ -511,7 +519,8 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) inet->inet_saddr = 0; /* Use device */ /* Make sure we are allowed to bind here. */ - if ((snum || !inet->bind_address_no_port) && + if ((snum || !(inet->bind_address_no_port || + force_bind_address_no_port)) && sk->sk_prot->get_port(sk, snum)) { inet->inet_saddr = inet->inet_rcv_saddr = 0; err = -EADDRINUSE; @@ -528,11 +537,11 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) sk_dst_reset(sk); err = 0; out_release_sock: - release_sock(sk); + if (with_lock) + release_sock(sk); out: return err; } -EXPORT_SYMBOL(inet_bind); int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, int addr_len, int flags) -- cgit v1.2.1 From d74bad4e74ee373787a9ae24197c17b7cdc428d5 Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Fri, 30 Mar 2018 15:08:05 -0700 Subject: bpf: Hooks for sys_connect == The problem == See description of the problem in the initial patch of this patch set. == The solution == The patch provides much more reliable in-kernel solution for the 2nd part of the problem: making outgoing connecttion from desired IP. It adds new attach types `BPF_CGROUP_INET4_CONNECT` and `BPF_CGROUP_INET6_CONNECT` for program type `BPF_PROG_TYPE_CGROUP_SOCK_ADDR` that can be used to override both source and destination of a connection at connect(2) time. Local end of connection can be bound to desired IP using newly introduced BPF-helper `bpf_bind()`. It allows to bind to only IP though, and doesn't support binding to port, i.e. leverages `IP_BIND_ADDRESS_NO_PORT` socket option. There are two reasons for this: * looking for a free port is expensive and can affect performance significantly; * there is no use-case for port. As for remote end (`struct sockaddr *` passed by user), both parts of it can be overridden, remote IP and remote port. It's useful if an application inside cgroup wants to connect to another application inside same cgroup or to itself, but knows nothing about IP assigned to the cgroup. Support is added for IPv4 and IPv6, for TCP and UDP. IPv4 and IPv6 have separate attach types for same reason as sys_bind hooks, i.e. to prevent reading from / writing to e.g. user_ip6 fields when user passes sockaddr_in since it'd be out-of-bound. == Implementation notes == The patch introduces new field in `struct proto`: `pre_connect` that is a pointer to a function with same signature as `connect` but is called before it. The reason is in some cases BPF hooks should be called way before control is passed to `sk->sk_prot->connect`. Specifically `inet_dgram_connect` autobinds socket before calling `sk->sk_prot->connect` and there is no way to call `bpf_bind()` from hooks from e.g. `ip4_datagram_connect` or `ip6_datagram_connect` since it'd cause double-bind. On the other hand `proto.pre_connect` provides a flexible way to add BPF hooks for connect only for necessary `proto` and call them at desired time before `connect`. Since `bpf_bind()` is allowed to bind only to IP and autobind in `inet_dgram_connect` binds only port there is no chance of double-bind. bpf_bind() sets `force_bind_address_no_port` to bind to only IP despite of value of `bind_address_no_port` socket field. bpf_bind() sets `with_lock` to `false` when calling to __inet_bind() and __inet6_bind() since all call-sites, where bpf_bind() is called, already hold socket lock. Signed-off-by: Andrey Ignatov Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- net/ipv4/af_inet.c | 13 +++++++++++++ net/ipv4/tcp_ipv4.c | 16 ++++++++++++++++ net/ipv4/udp.c | 14 ++++++++++++++ 3 files changed, 43 insertions(+) (limited to 'net/ipv4') diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index e203a39d6988..488fe26ac8e5 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -547,12 +547,19 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, int addr_len, int flags) { struct sock *sk = sock->sk; + int err; if (addr_len < sizeof(uaddr->sa_family)) return -EINVAL; if (uaddr->sa_family == AF_UNSPEC) return sk->sk_prot->disconnect(sk, flags); + if (BPF_CGROUP_PRE_CONNECT_ENABLED(sk)) { + err = sk->sk_prot->pre_connect(sk, uaddr, addr_len); + if (err) + return err; + } + if (!inet_sk(sk)->inet_num && inet_autobind(sk)) return -EAGAIN; return sk->sk_prot->connect(sk, uaddr, addr_len); @@ -633,6 +640,12 @@ int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr, if (sk->sk_state != TCP_CLOSE) goto out; + if (BPF_CGROUP_PRE_CONNECT_ENABLED(sk)) { + err = sk->sk_prot->pre_connect(sk, uaddr, addr_len); + if (err) + goto out; + } + err = sk->sk_prot->connect(sk, uaddr, addr_len); if (err < 0) goto out; diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 2c6aec2643e8..3c11d992d784 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -140,6 +140,21 @@ int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp) } EXPORT_SYMBOL_GPL(tcp_twsk_unique); +static int tcp_v4_pre_connect(struct sock *sk, struct sockaddr *uaddr, + int addr_len) +{ + /* This check is replicated from tcp_v4_connect() and intended to + * prevent BPF program called below from accessing bytes that are out + * of the bound specified by user in addr_len. + */ + if (addr_len < sizeof(struct sockaddr_in)) + return -EINVAL; + + sock_owned_by_me(sk); + + return BPF_CGROUP_RUN_PROG_INET4_CONNECT(sk, uaddr); +} + /* This will initiate an outgoing connection. */ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) { @@ -2409,6 +2424,7 @@ struct proto tcp_prot = { .name = "TCP", .owner = THIS_MODULE, .close = tcp_close, + .pre_connect = tcp_v4_pre_connect, .connect = tcp_v4_connect, .disconnect = tcp_disconnect, .accept = inet_csk_accept, diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 908fc02fb4f8..9c6c77fec963 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1658,6 +1658,19 @@ csum_copy_err: goto try_again; } +int udp_pre_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) +{ + /* This check is replicated from __ip4_datagram_connect() and + * intended to prevent BPF program called below from accessing bytes + * that are out of the bound specified by user in addr_len. + */ + if (addr_len < sizeof(struct sockaddr_in)) + return -EINVAL; + + return BPF_CGROUP_RUN_PROG_INET4_CONNECT_LOCK(sk, uaddr); +} +EXPORT_SYMBOL(udp_pre_connect); + int __udp_disconnect(struct sock *sk, int flags) { struct inet_sock *inet = inet_sk(sk); @@ -2530,6 +2543,7 @@ struct proto udp_prot = { .name = "UDP", .owner = THIS_MODULE, .close = udp_lib_close, + .pre_connect = udp_pre_connect, .connect = ip4_datagram_connect, .disconnect = udp_disconnect, .ioctl = udp_ioctl, -- cgit v1.2.1 From aac3fc320d9404f2665a8b1249dc3170d5fa3caf Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Fri, 30 Mar 2018 15:08:07 -0700 Subject: bpf: Post-hooks for sys_bind "Post-hooks" are hooks that are called right before returning from sys_bind. At this time IP and port are already allocated and no further changes to `struct sock` can happen before returning from sys_bind but BPF program has a chance to inspect the socket and change sys_bind result. Specifically it can e.g. inspect what port was allocated and if it doesn't satisfy some policy, BPF program can force sys_bind to fail and return EPERM to user. Another example of usage is recording the IP:port pair to some map to use it in later calls to sys_connect. E.g. if some TCP server inside cgroup was bound to some IP:port_n, it can be recorded to a map. And later when some TCP client inside same cgroup is trying to connect to 127.0.0.1:port_n, BPF hook for sys_connect can override the destination and connect application to IP:port_n instead of 127.0.0.1:port_n. That helps forcing all applications inside a cgroup to use desired IP and not break those applications if they e.g. use localhost to communicate between each other. == Implementation details == Post-hooks are implemented as two new attach types `BPF_CGROUP_INET4_POST_BIND` and `BPF_CGROUP_INET6_POST_BIND` for existing prog type `BPF_PROG_TYPE_CGROUP_SOCK`. Separate attach types for IPv4 and IPv6 are introduced to avoid access to IPv6 field in `struct sock` from `inet_bind()` and to IPv4 field from `inet6_bind()` since those fields might not make sense in such cases. Signed-off-by: Andrey Ignatov Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann --- net/ipv4/af_inet.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 488fe26ac8e5..142d4c35b493 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -519,12 +519,18 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len, inet->inet_saddr = 0; /* Use device */ /* Make sure we are allowed to bind here. */ - if ((snum || !(inet->bind_address_no_port || - force_bind_address_no_port)) && - sk->sk_prot->get_port(sk, snum)) { - inet->inet_saddr = inet->inet_rcv_saddr = 0; - err = -EADDRINUSE; - goto out_release_sock; + if (snum || !(inet->bind_address_no_port || + force_bind_address_no_port)) { + if (sk->sk_prot->get_port(sk, snum)) { + inet->inet_saddr = inet->inet_rcv_saddr = 0; + err = -EADDRINUSE; + goto out_release_sock; + } + err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk); + if (err) { + inet->inet_saddr = inet->inet_rcv_saddr = 0; + goto out_release_sock; + } } if (inet->inet_rcv_saddr) -- cgit v1.2.1