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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 /net/ipv6
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 'net/ipv6')
-rw-r--r--net/ipv6/udp.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 426c9d2b418d..9f729a7b8cf0 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1316,6 +1316,29 @@ do_udp_sendmsg:
fl6.saddr = np->saddr;
fl6.fl6_sport = inet->inet_sport;
+ if (cgroup_bpf_enabled && !connected) {
+ err = BPF_CGROUP_RUN_PROG_UDP6_SENDMSG_LOCK(sk,
+ (struct sockaddr *)sin6, &fl6.saddr);
+ if (err)
+ goto out_no_dst;
+ if (sin6) {
+ if (ipv6_addr_v4mapped(&sin6->sin6_addr)) {
+ /* BPF program rewrote IPv6-only by IPv4-mapped
+ * IPv6. It's currently unsupported.
+ */
+ err = -ENOTSUPP;
+ goto out_no_dst;
+ }
+ if (sin6->sin6_port == 0) {
+ /* BPF program set invalid port. Reject it. */
+ err = -EINVAL;
+ goto out_no_dst;
+ }
+ fl6.fl6_dport = sin6->sin6_port;
+ fl6.daddr = sin6->sin6_addr;
+ }
+ }
+
final_p = fl6_update_dst(&fl6, opt, &final);
if (final_p)
connected = false;
@@ -1395,6 +1418,7 @@ do_append_data:
out:
dst_release(dst);
+out_no_dst:
fl6_sock_release(flowlabel);
txopt_put(opt_to_free);
if (!err)