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author | Andrey Ignatov <rdna@fb.com> | 2018-05-25 18:55:23 +0300 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-05-28 18:41:02 +0300 |
commit | 1cedee13d25ab118d325f95588c1a084e9317229 (patch) | |
tree | 63f5cd82b008d63091bac31168253e3af6a1ba6c /include/uapi/linux/bpf.h | |
parent | 13193b0f392f5a65d0d54185cb95ed5e99c0a5bf (diff) | |
download | linux-1cedee13d25ab118d325f95588c1a084e9317229.tar.xz |
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 'include/uapi/linux/bpf.h')
-rw-r--r-- | include/uapi/linux/bpf.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 9b8c6e310e9a..cc68787f2d97 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -160,6 +160,8 @@ enum bpf_attach_type { BPF_CGROUP_INET6_CONNECT, BPF_CGROUP_INET4_POST_BIND, BPF_CGROUP_INET6_POST_BIND, + BPF_CGROUP_UDP4_SENDMSG, + BPF_CGROUP_UDP6_SENDMSG, __MAX_BPF_ATTACH_TYPE }; @@ -2363,6 +2365,12 @@ struct bpf_sock_addr { __u32 family; /* Allows 4-byte read, but no write */ __u32 type; /* Allows 4-byte read, but no write */ __u32 protocol; /* Allows 4-byte read, but no write */ + __u32 msg_src_ip4; /* Allows 1,2,4-byte read an 4-byte write. + * Stored in network byte order. + */ + __u32 msg_src_ip6[4]; /* Allows 1,2,4-byte read an 4-byte write. + * Stored in network byte order. + */ }; /* User bpf_sock_ops struct to access socket values and specify request ops |