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authorAndrey Ignatov <rdna@fb.com>2018-05-25 08:55:23 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2018-05-28 17:41:02 +0200
commit1cedee13d25ab118d325f95588c1a084e9317229 (patch)
tree63f5cd82b008d63091bac31168253e3af6a1ba6c /kernel/bpf/cgroup.c
parent13193b0f392f5a65d0d54185cb95ed5e99c0a5bf (diff)
downloadlinux-1cedee13d25ab118d325f95588c1a084e9317229.tar.bz2
bpf: Hooks for sys_sendmsg
In addition to already existing BPF hooks for sys_bind and sys_connect, the patch provides new hooks for sys_sendmsg. It leverages existing BPF program type `BPF_PROG_TYPE_CGROUP_SOCK_ADDR` that provides access to socket itlself (properties like family, type, protocol) and user-passed `struct sockaddr *` so that BPF program can override destination IP and port for system calls such as sendto(2) or sendmsg(2) and/or assign source IP to the socket. The hooks are implemented as two new attach types: `BPF_CGROUP_UDP4_SENDMSG` and `BPF_CGROUP_UDP6_SENDMSG` for UDPv4 and UDPv6 correspondingly. UDPv4 and UDPv6 separate attach types for same reason as sys_bind and sys_connect 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. The difference with already existing hooks is sys_sendmsg are implemented only for unconnected UDP. For TCP it doesn't make sense to change user-provided `struct sockaddr *` at sendto(2)/sendmsg(2) time since socket either was already connected and has source/destination set or wasn't connected and call to sendto(2)/sendmsg(2) would lead to ENOTCONN anyway. Connected UDP is already handled by sys_connect hooks that can override source/destination at connect time and use fast-path later, i.e. these hooks don't affect UDP fast-path. Rewriting source IP is implemented differently than that in sys_connect hooks. When sys_sendmsg is used with unconnected UDP it doesn't work to just bind socket to desired local IP address since source IP can be set on per-packet basis by using ancillary data (cmsg(3)). So no matter if socket is bound or not, source IP has to be rewritten on every call to sys_sendmsg. To do so two new fields are added to UAPI `struct bpf_sock_addr`; * `msg_src_ip4` to set source IPv4 for UDPv4; * `msg_src_ip6` to set source IPv6 for UDPv6. Signed-off-by: Andrey Ignatov <rdna@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel/bpf/cgroup.c')
-rw-r--r--kernel/bpf/cgroup.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 43171a0bb02b..f7c00bd6f8e4 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -500,6 +500,7 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
* @sk: sock struct that will use sockaddr
* @uaddr: sockaddr struct provided by user
* @type: The type of program to be exectuted
+ * @t_ctx: Pointer to attach type specific context
*
* socket is expected to be of type INET or INET6.
*
@@ -508,12 +509,15 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
*/
int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
struct sockaddr *uaddr,
- enum bpf_attach_type type)
+ enum bpf_attach_type type,
+ void *t_ctx)
{
struct bpf_sock_addr_kern ctx = {
.sk = sk,
.uaddr = uaddr,
+ .t_ctx = t_ctx,
};
+ struct sockaddr_storage unspec;
struct cgroup *cgrp;
int ret;
@@ -523,6 +527,11 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
if (sk->sk_family != AF_INET && sk->sk_family != AF_INET6)
return 0;
+ if (!ctx.uaddr) {
+ memset(&unspec, 0, sizeof(unspec));
+ ctx.uaddr = (struct sockaddr *)&unspec;
+ }
+
cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, BPF_PROG_RUN);