flow_dissector: extract more ICMP information

The ICMP flow dissector currently parses only the Type and Code fields.
Some ICMP packets (echo, timestamp) have a 16 bit Identifier field which
is used to correlate packets.
Add such field in flow_dissector_key_icmp and replace skb_flow_get_be16()
with a more complex function which populate this field.

Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index 7747af3cc5006f065e6a8d98f1861599813d1451..f8541d018848c0e7c923da056ca9dff912cb29f8 100644 (file)
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -6,6 +6,8 @@
 #include <linux/in6.h>
 #include <uapi/linux/if_ether.h>
 
+struct sk_buff;
+
 /**
  * struct flow_dissector_key_control:
  * @thoff: Transport header offset
@@ -156,19 +158,16 @@ struct flow_dissector_key_ports {
 
 /**
  * flow_dissector_key_icmp:
- *     @ports: type and code of ICMP header
- *             icmp: ICMP type (high) and code (low)
  *             type: ICMP type
  *             code: ICMP code
+ *             id:   session identifier
  */
 struct flow_dissector_key_icmp {
-       union {
-               __be16 icmp;
-               struct {
-                       u8 type;
-                       u8 code;
-               };
+       struct {
+               u8 type;
+               u8 code;
        };
+       u16 id;
 };
 
 /**
@@ -282,6 +281,7 @@ struct flow_keys {
        struct flow_dissector_key_vlan cvlan;
        struct flow_dissector_key_keyid keyid;
        struct flow_dissector_key_ports ports;
+       struct flow_dissector_key_icmp icmp;
        /* 'addrs' must be the last member */
        struct flow_dissector_key_addrs addrs;
 };
@@ -316,6 +316,9 @@ static inline bool flow_keys_have_l4(const struct flow_keys *keys)
 }
 
 u32 flow_hash_from_keys(struct flow_keys *keys);
+void skb_flow_get_icmp_tci(const struct sk_buff *skb,
+                          struct flow_dissector_key_icmp *key_icmp,
+                          void *data, int thoff, int hlen);
 
 static inline bool dissector_uses_key(const struct flow_dissector *flow_dissector,
                                      enum flow_dissector_key_id key_id)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 0fb721976f3d98fd6a2cf3ed822873730ce8a845..0807df0bde021983efbfa8aafa8e1832ad6332ec 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -178,27 +178,6 @@ int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
        mutex_unlock(&flow_dissector_mutex);
        return 0;
 }
-/**
- * skb_flow_get_be16 - extract be16 entity
- * @skb: sk_buff to extract from
- * @poff: offset to extract at
- * @data: raw buffer pointer to the packet
- * @hlen: packet header length
- *
- * The function will try to retrieve a be32 entity at
- * offset poff
- */
-static __be16 skb_flow_get_be16(const struct sk_buff *skb, int poff,
-                               void *data, int hlen)
-{
-       __be16 *u, _u;
-
-       u = __skb_header_pointer(skb, poff, sizeof(_u), data, hlen, &_u);
-       if (u)
-               return *u;
-
-       return 0;
-}
 
 /**
  * __skb_flow_get_ports - extract the upper layer ports and return them
@@ -234,8 +213,54 @@ __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
 }
 EXPORT_SYMBOL(__skb_flow_get_ports);
 
-/* If FLOW_DISSECTOR_KEY_ICMP is set, get the Type and Code from an ICMP packet
- * using skb_flow_get_be16().
+static bool icmp_has_id(u8 type)
+{
+       switch (type) {
+       case ICMP_ECHO:
+       case ICMP_ECHOREPLY:
+       case ICMP_TIMESTAMP:
+       case ICMP_TIMESTAMPREPLY:
+       case ICMPV6_ECHO_REQUEST:
+       case ICMPV6_ECHO_REPLY:
+               return true;
+       }
+
+       return false;
+}
+
+/**
+ * skb_flow_get_icmp_tci - extract ICMP(6) Type, Code and Identifier fields
+ * @skb: sk_buff to extract from
+ * @key_icmp: struct flow_dissector_key_icmp to fill
+ * @data: raw buffer pointer to the packet
+ * @toff: offset to extract at
+ * @hlen: packet header length
+ */
+void skb_flow_get_icmp_tci(const struct sk_buff *skb,
+                          struct flow_dissector_key_icmp *key_icmp,
+                          void *data, int thoff, int hlen)
+{
+       struct icmphdr *ih, _ih;
+
+       ih = __skb_header_pointer(skb, thoff, sizeof(_ih), data, hlen, &_ih);
+       if (!ih)
+               return;
+
+       key_icmp->type = ih->type;
+       key_icmp->code = ih->code;
+
+       /* As we use 0 to signal that the Id field is not present,
+        * avoid confusion with packets without such field
+        */
+       if (icmp_has_id(ih->type))
+               key_icmp->id = ih->un.echo.id ? : 1;
+       else
+               key_icmp->id = 0;
+}
+EXPORT_SYMBOL(skb_flow_get_icmp_tci);
+
+/* If FLOW_DISSECTOR_KEY_ICMP is set, dissect an ICMP packet
+ * using skb_flow_get_icmp_tci().
  */
 static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
                                    struct flow_dissector *flow_dissector,
@@ -250,7 +275,8 @@ static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
        key_icmp = skb_flow_dissector_target(flow_dissector,
                                             FLOW_DISSECTOR_KEY_ICMP,
                                             target_container);
-       key_icmp->icmp = skb_flow_get_be16(skb, thoff, data, hlen);
+
+       skb_flow_get_icmp_tci(skb, key_icmp, data, thoff, hlen);
 }
 
 void skb_flow_dissect_meta(const struct sk_buff *skb,