net: plumb network namespace into __skb_flow_dissect

This new argument will be used in the next patches for the
eth_get_headlen use case. eth_get_headlen calls flow dissector
with only data (without skb) so there is currently no way to
pull attached BPF flow dissector program. With this new argument,
we can amend the callers to explicitly pass network namespace
so we can use attached BPF program.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2b7b8228c5c353354e27829f33202fe0b1ffcad4..b466fbface2ec555c6e6bbdd01cf61df4caf16ed 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1284,7 +1284,8 @@ bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
                            const struct sk_buff *skb,
                            struct flow_dissector *flow_dissector,
                            struct bpf_flow_keys *flow_keys);
-bool __skb_flow_dissect(const struct sk_buff *skb,
+bool __skb_flow_dissect(const struct net *net,
+                       const struct sk_buff *skb,
                        struct flow_dissector *flow_dissector,
                        void *target_container,
                        void *data, __be16 proto, int nhoff, int hlen,
@@ -1294,8 +1295,8 @@ static inline bool skb_flow_dissect(const struct sk_buff *skb,
                                    struct flow_dissector *flow_dissector,
                                    void *target_container, unsigned int flags)
 {
-       return __skb_flow_dissect(skb, flow_dissector, target_container,
-                                 NULL, 0, 0, 0, flags);
+       return __skb_flow_dissect(NULL, skb, flow_dissector,
+                                 target_container, NULL, 0, 0, 0, flags);
 }
 
 static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
@@ -1303,18 +1304,19 @@ static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb,
                                              unsigned int flags)
 {
        memset(flow, 0, sizeof(*flow));
-       return __skb_flow_dissect(skb, &flow_keys_dissector, flow,
-                                 NULL, 0, 0, 0, flags);
+       return __skb_flow_dissect(NULL, skb, &flow_keys_dissector,
+                                 flow, NULL, 0, 0, 0, flags);
 }
 
 static inline bool
-skb_flow_dissect_flow_keys_basic(const struct sk_buff *skb,
+skb_flow_dissect_flow_keys_basic(const struct net *net,
+                                const struct sk_buff *skb,
                                 struct flow_keys_basic *flow, void *data,
                                 __be16 proto, int nhoff, int hlen,
                                 unsigned int flags)
 {
        memset(flow, 0, sizeof(*flow));
-       return __skb_flow_dissect(skb, &flow_keys_basic_dissector, flow,
+       return __skb_flow_dissect(net, skb, &flow_keys_basic_dissector, flow,
                                  data, proto, nhoff, hlen, flags);
 }
 
@@ -2492,7 +2494,8 @@ static inline void skb_probe_transport_header(struct sk_buff *skb)
        if (skb_transport_header_was_set(skb))
                return;
 
-       if (skb_flow_dissect_flow_keys_basic(skb, &keys, NULL, 0, 0, 0, 0))
+       if (skb_flow_dissect_flow_keys_basic(NULL, skb, &keys,
+                                            NULL, 0, 0, 0, 0))
                skb_set_transport_header(skb, keys.control.thoff);
 }
 

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index ef6d9443cc7577731987490149cd6bf166d3b8c0..f32c7e737fc631da038c272a5f109f92b5f27b6d 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -722,6 +722,7 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
 
 /**
  * __skb_flow_dissect - extract the flow_keys struct and return it
+ * @net: associated network namespace, derived from @skb if NULL
  * @skb: sk_buff to extract the flow from, can be NULL if the rest are specified
  * @flow_dissector: list of keys to dissect
  * @target_container: target structure to put dissected values into
@@ -738,7 +739,8 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
  *
  * Caller must take care of zeroing target container memory.
  */
-bool __skb_flow_dissect(const struct sk_buff *skb,
+bool __skb_flow_dissect(const struct net *net,
+                       const struct sk_buff *skb,
                        struct flow_dissector *flow_dissector,
                        void *target_container,
                        void *data, __be16 proto, int nhoff, int hlen,
@@ -797,13 +799,17 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
                struct bpf_prog *attached = NULL;
 
                rcu_read_lock();
+               if (!net) {
+                       if (skb->dev)
+                               net = dev_net(skb->dev);
+                       else if (skb->sk)
+                               net = sock_net(skb->sk);
+                       else
+                               WARN_ON_ONCE(1);
+               }
 
-               if (skb->dev)
-                       attached = rcu_dereference(dev_net(skb->dev)->flow_dissector_prog);
-               else if (skb->sk)
-                       attached = rcu_dereference(sock_net(skb->sk)->flow_dissector_prog);
-               else
-                       WARN_ON_ONCE(1);
+               if (net)
+                       attached = rcu_dereference(net->flow_dissector_prog);
 
                if (attached) {
                        ret = __skb_flow_bpf_dissect(attached, skb,
@@ -1405,8 +1411,8 @@ u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
        __flow_hash_secret_init();
 
        memset(&keys, 0, sizeof(keys));
-       __skb_flow_dissect(skb, &flow_keys_dissector_symmetric, &keys,
-                          NULL, 0, 0, 0,
+       __skb_flow_dissect(NULL, skb, &flow_keys_dissector_symmetric,
+                          &keys, NULL, 0, 0, 0,
                           FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
 
        return __flow_hash_from_keys(&keys, hashrnd);
@@ -1507,7 +1513,8 @@ u32 skb_get_poff(const struct sk_buff *skb)
 {
        struct flow_keys_basic keys;
 
-       if (!skb_flow_dissect_flow_keys_basic(skb, &keys, NULL, 0, 0, 0, 0))
+       if (!skb_flow_dissect_flow_keys_basic(NULL, skb, &keys,
+                                             NULL, 0, 0, 0, 0))
                return 0;
 
        return __skb_get_poff(skb, skb->data, &keys, skb_headlen(skb));

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index f7a3d7a171c78419421b3976d9d510bbd701236c..1e439549c419b74aaee296e231f76eb016037dca 100644 (file)
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -136,8 +136,9 @@ u32 eth_get_headlen(void *data, unsigned int len)
                return len;
 
        /* parse any remaining L2/L3 headers, check for L4 */
-       if (!skb_flow_dissect_flow_keys_basic(NULL, &keys, data, eth->h_proto,
-                                             sizeof(*eth), len, flags))
+       if (!skb_flow_dissect_flow_keys_basic(NULL, NULL, &keys, data,
+                                             eth->h_proto, sizeof(*eth),
+                                             len, flags))
                return max_t(u32, keys.control.thoff, sizeof(*eth));
 
        /* parse for any L4 headers */