path: root/net/ipv4
diff options
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/ipv4
parentbpf: Define cgroup_bpf_enabled for CONFIG_CGROUP_BPF=n (diff)
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/ipv4')
1 files changed, 18 insertions, 2 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d71f1f3e1155..3c27d00b5730 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -901,6 +901,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
struct inet_sock *inet = inet_sk(sk);
struct udp_sock *up = udp_sk(sk);
+ DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
struct flowi4 fl4_stack;
struct flowi4 *fl4;
int ulen = len;
@@ -955,8 +956,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
* Get and verify the address.
- if (msg->msg_name) {
- DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
+ if (usin) {
if (msg->msg_namelen < sizeof(*usin))
return -EINVAL;
if (usin->sin_family != AF_INET) {
@@ -1010,6 +1010,22 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+ if (cgroup_bpf_enabled && !connected) {
+ (struct sockaddr *)usin, &ipc.addr);
+ if (err)
+ goto out_free;
+ if (usin) {
+ if (usin->sin_port == 0) {
+ /* BPF program set invalid port. Reject it. */
+ err = -EINVAL;
+ goto out_free;
+ }
+ daddr = usin->sin_addr.s_addr;
+ dport = usin->sin_port;
+ }
+ }
saddr = ipc.addr;
ipc.addr = faddr = daddr;