David Ahern and Nicolas Dichtel report that the handling of the netns id
0 is incorrect for the BPF socket lookup helpers: rather than finding
the netns with id 0, it is resolving to the current netns. This renders
the netns_id 0 inaccessible.
To fix this, adjust the API for the netns to treat all u32 values with
the highest bit set (BPF_F_SK_CURRENT_NS) as a lookup in the current
netns, while any values with a lower value (including zero) would result
in a lookup for a socket in the netns corresponding to that id. As
before, if the netns with that ID does not exist, no socket will be
found.
Signed-off-by: Joe Stringer <j...@wand.net.nz>
---
include/uapi/linux/bpf.h | 29 +++++++++-------
net/core/filter.c | 16 ++++-----
tools/include/uapi/linux/bpf.h | 33 ++++++++++++-------
.../selftests/bpf/test_sk_lookup_kern.c | 18 +++++-----
4 files changed, 55 insertions(+), 41 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 852dc17ab47a..543945d520b9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2187,12 +2187,13 @@ union bpf_attr {
* **sizeof**\ (*tuple*\ **->ipv6**)
* Look for an IPv6 socket.
*
- * If the *netns* is zero, then the socket lookup table in the
- * netns associated with the *ctx* will be used. For the TC hooks,
- * this in the netns of the device in the skb. For socket hooks,
- * this in the netns of the socket. If *netns* is non-zero, then
- * it specifies the ID of the netns relative to the netns
- * associated with the *ctx*.
+ * If the *netns* is **BPF_F_SK_CURRENT_NS** or greater, then the
+ * socket lookup table in the netns associated with the *ctx* will
+ * will be used. For the TC hooks, this is the netns of the device
+ * in the skb. For socket hooks, this is the netns of the socket.
+ * If *netns* is less than **BPF_F_SK_CURRENT_NS**, then it
+ * specifies the ID of the netns relative to the netns associated
+ * with the *ctx*.
*
* All values for *flags* are reserved for future usage, and must
* be left at zero.
@@ -2219,12 +2220,13 @@ union bpf_attr {
* **sizeof**\ (*tuple*\ **->ipv6**)
* Look for an IPv6 socket.
*
- * If the *netns* is zero, then the socket lookup table in the
- * netns associated with the *ctx* will be used. For the TC hooks,
- * this in the netns of the device in the skb. For socket hooks,
- * this in the netns of the socket. If *netns* is non-zero, then
- * it specifies the ID of the netns relative to the netns
- * associated with the *ctx*.
+ * If the *netns* is **BPF_F_SK_CURRENT_NS** or greater, then the
+ * socket lookup table in the netns associated with the *ctx* will
+ * will be used. For the TC hooks, this is the netns of the device
+ * in the skb. For socket hooks, this is the netns of the socket.
+ * If *netns* is less than **BPF_F_SK_CURRENT_NS**, then it
+ * specifies the ID of the netns relative to the netns associated
+ * with the *ctx*.
*
* All values for *flags* are reserved for future usage, and must
* be left at zero.
@@ -2405,6 +2407,9 @@ enum bpf_func_id {
/* BPF_FUNC_perf_event_output for sk_buff input context. */
#define BPF_F_CTXLEN_MASK (0xfffffULL << 32)
+/* BPF_FUNC_sk_lookup_tcp and BPF_FUNC_sk_lookup_udp flags. */
+#define BPF_F_SK_CURRENT_NS 0x80000000 /* For netns field */
+
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
diff --git a/net/core/filter.c b/net/core/filter.c
index 9a1327eb25fa..8c8a7ad3f5e6 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4882,7 +4882,7 @@ static struct sock *sk_lookup(struct net *net, struct
bpf_sock_tuple *tuple,
*/
static unsigned long
bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
- u8 proto, u64 netns_id, u64 flags)
+ u8 proto, u32 netns_id, u64 flags)
{
struct net *caller_net;
struct sock *sk = NULL;
@@ -4890,22 +4890,22 @@ bpf_sk_lookup(struct sk_buff *skb, struct
bpf_sock_tuple *tuple, u32 len,
struct net *net;
family = len == sizeof(tuple->ipv4) ? AF_INET : AF_INET6;
- if (unlikely(family == AF_UNSPEC || netns_id > U32_MAX || flags))
+ if (unlikely(family == AF_UNSPEC || flags))
goto out;
if (skb->dev)
caller_net = dev_net(skb->dev);
else
caller_net = sock_net(skb->sk);
- if (netns_id) {
+ if (netns_id & BPF_F_SK_CURRENT_NS) {
+ net = caller_net;
+ sk = sk_lookup(net, tuple, skb, family, proto);
+ } else {
net = get_net_ns_by_id(caller_net, netns_id);
if (unlikely(!net))
goto out;
sk = sk_lookup(net, tuple, skb, family, proto);
put_net(net);
- } else {
- net = caller_net;
- sk = sk_lookup(net, tuple, skb, family, proto);
}
if (sk)
@@ -4915,7 +4915,7 @@ bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple
*tuple, u32 len,
}
BPF_CALL_5(bpf_sk_lookup_tcp, struct sk_buff *, skb,
- struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
+ struct bpf_sock_tuple *, tuple, u32, len, u32, netns_id, u64, flags)
{
return bpf_sk_lookup(skb, tuple, len, IPPROTO_TCP, netns_id, flags);
}
@@ -4933,7 +4933,7 @@ static const struct bpf_func_proto
bpf_sk_lookup_tcp_proto = {
};
BPF_CALL_5(bpf_sk_lookup_udp, struct sk_buff *, skb,
- struct bpf_sock_tuple *, tuple, u32, len, u64, netns_id, u64, flags)
+ struct bpf_sock_tuple *, tuple, u32, len, u32, netns_id, u64, flags)
{
return bpf_sk_lookup(skb, tuple, len, IPPROTO_UDP, netns_id, flags);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 852dc17ab47a..73649732513d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2187,12 +2187,13 @@ union bpf_attr {
* **sizeof**\ (*tuple*\ **->ipv6**)
* Look for an IPv6 socket.
*
- * If the *netns* is zero, then the socket lookup table in the
- * netns associated with the *ctx* will be used. For the TC hooks,
- * this in the netns of the device in the skb. For socket hooks,
- * this in the netns of the socket. If *netns* is non-zero, then
- * it specifies the ID of the netns relative to the netns
- * associated with the *ctx*.
+ * If the *netns* is **BPF_F_SK_CURRENT_NS** or greater, then the
+ * socket lookup table in the netns associated with the *ctx* will
+ * will be used. For the TC hooks, this is the netns of the device
+ * in the skb. For socket hooks, this is the netns of the socket.
+ * If *netns* is less than **BPF_F_SK_CURRENT_NS**, then it
+ * specifies the ID of the netns relative to the netns associated
+ * with the *ctx*.
*
* All values for *flags* are reserved for future usage, and must
* be left at zero.
@@ -2201,6 +2202,8 @@ union bpf_attr {
* **CONFIG_NET** configuration option.
* Return
* Pointer to *struct bpf_sock*, or NULL in case of failure.
+ * For sockets with reuseport option, *struct bpf_sock*
+ * return is from reuse->socks[] using hash of the packet.
*
* struct bpf_sock *bpf_sk_lookup_udp(void *ctx, struct bpf_sock_tuple *tuple,
u32 tuple_size, u32 netns, u64 flags)
* Description
@@ -2219,12 +2222,13 @@ union bpf_attr {
* **sizeof**\ (*tuple*\ **->ipv6**)
* Look for an IPv6 socket.
*
- * If the *netns* is zero, then the socket lookup table in the
- * netns associated with the *ctx* will be used. For the TC hooks,
- * this in the netns of the device in the skb. For socket hooks,
- * this in the netns of the socket. If *netns* is non-zero, then
- * it specifies the ID of the netns relative to the netns
- * associated with the *ctx*.
+ * If the *netns* is **BPF_F_SK_CURRENT_NS** or greater, then the
+ * socket lookup table in the netns associated with the *ctx* will
+ * will be used. For the TC hooks, this is the netns of the device
+ * in the skb. For socket hooks, this is the netns of the socket.
+ * If *netns* is less than **BPF_F_SK_CURRENT_NS**, then it
+ * specifies the ID of the netns relative to the netns associated
+ * with the *ctx*.
*
* All values for *flags* are reserved for future usage, and must
* be left at zero.
@@ -2233,6 +2237,8 @@ union bpf_attr {
* **CONFIG_NET** configuration option.
* Return
* Pointer to *struct bpf_sock*, or NULL in case of failure.
+ * For sockets with reuseport option, *struct bpf_sock*
+ * return is from reuse->socks[] using hash of the packet.
*
* int bpf_sk_release(struct bpf_sock *sk)
* Description
@@ -2405,6 +2411,9 @@ enum bpf_func_id {
/* BPF_FUNC_perf_event_output for sk_buff input context. */
#define BPF_F_CTXLEN_MASK (0xfffffULL << 32)
+/* BPF_FUNC_sk_lookup_tcp and BPF_FUNC_sk_lookup_udp flags. */
+#define BPF_F_SK_CURRENT_NS 0x80000000 /* For netns field */
+
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
diff --git a/tools/testing/selftests/bpf/test_sk_lookup_kern.c
b/tools/testing/selftests/bpf/test_sk_lookup_kern.c
index b745bdc08c2b..673073d1a9eb 100644
--- a/tools/testing/selftests/bpf/test_sk_lookup_kern.c
+++ b/tools/testing/selftests/bpf/test_sk_lookup_kern.c
@@ -72,7 +72,7 @@ int bpf_sk_lookup_test0(struct __sk_buff *skb)
return TC_ACT_SHOT;
tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6);
- sk = bpf_sk_lookup_tcp(skb, tuple, tuple_len, 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, tuple, tuple_len, BPF_F_SK_CURRENT_NS, 0);
if (sk)
bpf_sk_release(sk);
return sk ? TC_ACT_OK : TC_ACT_UNSPEC;
@@ -84,7 +84,7 @@ int bpf_sk_lookup_test1(struct __sk_buff *skb)
struct bpf_sock_tuple tuple = {};
struct bpf_sock *sk;
- sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS,
0);
if (sk)
bpf_sk_release(sk);
return 0;
@@ -97,7 +97,7 @@ int bpf_sk_lookup_uaf(struct __sk_buff *skb)
struct bpf_sock *sk;
__u32 family = 0;
- sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS,
0);
if (sk) {
bpf_sk_release(sk);
family = sk->family;
@@ -112,7 +112,7 @@ int bpf_sk_lookup_modptr(struct __sk_buff *skb)
struct bpf_sock *sk;
__u32 family;
- sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS,
0);
if (sk) {
sk += 1;
bpf_sk_release(sk);
@@ -127,7 +127,7 @@ int bpf_sk_lookup_modptr_or_null(struct __sk_buff *skb)
struct bpf_sock *sk;
__u32 family;
- sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS,
0);
sk += 1;
if (sk)
bpf_sk_release(sk);
@@ -139,7 +139,7 @@ int bpf_sk_lookup_test2(struct __sk_buff *skb)
{
struct bpf_sock_tuple tuple = {};
- bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS, 0);
return 0;
}
@@ -149,7 +149,7 @@ int bpf_sk_lookup_test3(struct __sk_buff *skb)
struct bpf_sock_tuple tuple = {};
struct bpf_sock *sk;
- sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS,
0);
bpf_sk_release(sk);
bpf_sk_release(sk);
return 0;
@@ -161,7 +161,7 @@ int bpf_sk_lookup_test4(struct __sk_buff *skb)
struct bpf_sock_tuple tuple = {};
struct bpf_sock *sk;
- sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS,
0);
bpf_sk_release(sk);
return 0;
}
@@ -169,7 +169,7 @@ int bpf_sk_lookup_test4(struct __sk_buff *skb)
void lookup_no_release(struct __sk_buff *skb)
{
struct bpf_sock_tuple tuple = {};
- bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
+ bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_SK_CURRENT_NS, 0);
}
SEC("fail_no_release_subcall")
--
2.17.1
