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Description
I've used a bindgen to generate bindings to the sk_buff structure and I've got 2 identical variables in different __BindgenUnionField.
Original C structure:
struct sk_buff {
union {
struct {
/* These two members must be first to match sk_buff_head. */
struct sk_buff *next;
struct sk_buff *prev;
union {
struct net_device *dev;
/* Some protocols might use this space to store information,
* while device pointer would be NULL.
* UDP receive path is one user.
*/
unsigned long dev_scratch;
};
};
struct rb_node rbnode; /* used in netem, ip4 defrag, and tcp stack */
struct list_head list;
struct llist_node ll_node;
};
struct sock *sk;
union {
ktime_t tstamp;
u64 skb_mstamp_ns; /* earliest departure time */
};
/*
* This is the control buffer. It is free to use for every
* layer. Please put your private variables there. If you
* want to keep them across layers you have to do a skb_clone()
* first. This is owned by whoever has the skb queued ATM.
*/
char cb[48] __aligned(8);
union {
struct {
unsigned long _skb_refdst;
void (*destructor)(struct sk_buff *skb);
};
struct list_head tcp_tsorted_anchor;
#ifdef CONFIG_NET_SOCK_MSG
unsigned long _sk_redir;
#endif
};
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
unsigned long _nfct;
#endif
unsigned int len,
data_len;
__u16 mac_len,
hdr_len;
/* Following fields are _not_ copied in __copy_skb_header()
* Note that queue_mapping is here mostly to fill a hole.
*/
__u16 queue_mapping;
/* if you move cloned around you also must adapt those constants */
#ifdef __BIG_ENDIAN_BITFIELD
#define CLONED_MASK (1 << 7)
#else
#define CLONED_MASK 1
#endif
#define CLONED_OFFSET offsetof(struct sk_buff, __cloned_offset)
/* private: */
__u8 __cloned_offset[0];
/* public: */
__u8 cloned:1,
nohdr:1,
fclone:2,
peeked:1,
head_frag:1,
pfmemalloc:1,
pp_recycle:1; /* page_pool recycle indicator */
#ifdef CONFIG_SKB_EXTENSIONS
__u8 active_extensions;
#endif
/* Fields enclosed in headers group are copied
* using a single memcpy() in __copy_skb_header()
*/
struct_group(headers,
/* private: */
__u8 __pkt_type_offset[0];
/* public: */
__u8 pkt_type:3; /* see PKT_TYPE_MAX */
__u8 ignore_df:1;
__u8 dst_pending_confirm:1;
__u8 ip_summed:2;
__u8 ooo_okay:1;
/* private: */
__u8 __mono_tc_offset[0];
/* public: */
__u8 mono_delivery_time:1; /* See SKB_MONO_DELIVERY_TIME_MASK */
#ifdef CONFIG_NET_XGRESS
__u8 tc_at_ingress:1; /* See TC_AT_INGRESS_MASK */
__u8 tc_skip_classify:1;
#endif
__u8 remcsum_offload:1;
__u8 csum_complete_sw:1;
__u8 csum_level:2;
__u8 inner_protocol_type:1;
__u8 l4_hash:1;
__u8 sw_hash:1;
#ifdef CONFIG_WIRELESS
__u8 wifi_acked_valid:1;
__u8 wifi_acked:1;
#endif
__u8 no_fcs:1;
/* Indicates the inner headers are valid in the skbuff. */
__u8 encapsulation:1;
__u8 encap_hdr_csum:1;
__u8 csum_valid:1;
#ifdef CONFIG_IPV6_NDISC_NODETYPE
__u8 ndisc_nodetype:2;
#endif
#if IS_ENABLED(CONFIG_IP_VS)
__u8 ipvs_property:1;
#endif
#if IS_ENABLED(CONFIG_NETFILTER_XT_TARGET_TRACE) || IS_ENABLED(CONFIG_NF_TABLES)
__u8 nf_trace:1;
#endif
#ifdef CONFIG_NET_SWITCHDEV
__u8 offload_fwd_mark:1;
__u8 offload_l3_fwd_mark:1;
#endif
__u8 redirected:1;
#ifdef CONFIG_NET_REDIRECT
__u8 from_ingress:1;
#endif
#ifdef CONFIG_NETFILTER_SKIP_EGRESS
__u8 nf_skip_egress:1;
#endif
#ifdef CONFIG_TLS_DEVICE
__u8 decrypted:1;
#endif
__u8 slow_gro:1;
#if IS_ENABLED(CONFIG_IP_SCTP)
__u8 csum_not_inet:1;
#endif
#if defined(CONFIG_NET_SCHED) || defined(CONFIG_NET_XGRESS)
__u16 tc_index; /* traffic control index */
#endif
u16 alloc_cpu;
union {
__wsum csum;
struct {
__u16 csum_start;
__u16 csum_offset;
};
};
__u32 priority;
int skb_iif;
__u32 hash;
union {
u32 vlan_all;
struct {
__be16 vlan_proto;
__u16 vlan_tci;
};
};
#if defined(CONFIG_NET_RX_BUSY_POLL) || defined(CONFIG_XPS)
union {
unsigned int napi_id;
unsigned int sender_cpu;
};
#endif
#ifdef CONFIG_NETWORK_SECMARK
__u32 secmark;
#endif
union {
__u32 mark;
__u32 reserved_tailroom;
};
union {
__be16 inner_protocol;
__u8 inner_ipproto;
};
__u16 inner_transport_header;
__u16 inner_network_header;
__u16 inner_mac_header;
__be16 protocol;
__u16 transport_header;
__u16 network_header;
__u16 mac_header;
#ifdef CONFIG_KCOV
u64 kcov_handle;
#endif
); /* end headers group */
/* These elements must be at the end, see alloc_skb() for details. */
sk_buff_data_t tail;
sk_buff_data_t end;
unsigned char *head,
*data;
unsigned int truesize;
refcount_t users;
#ifdef CONFIG_SKB_EXTENSIONS
/* only usable after checking ->active_extensions != 0 */
struct skb_ext *extensions;
#endif
};Output bindings:
#[repr(C)]
pub struct sk_buff {
pub __bindgen_anon_1: sk_buff__bindgen_ty_1,
pub sk: *mut sock,
pub __bindgen_anon_2: sk_buff__bindgen_ty_2,
pub cb: [core::ffi::c_char; 48usize],
pub __bindgen_anon_3: sk_buff__bindgen_ty_3,
pub len: core::ffi::c_uint,
pub data_len: core::ffi::c_uint,
pub mac_len: __u16,
pub hdr_len: __u16,
pub queue_mapping: __u16,
pub __cloned_offset: __IncompleteArrayField<__u8>,
pub _bitfield_align_1: [u8; 0],
pub _bitfield_1: __BindgenBitfieldUnit<[u8; 1usize]>,
pub active_extensions: __u8,
pub __bindgen_anon_4: sk_buff__bindgen_ty_4, // values are in this structure
pub tail: sk_buff_data_t,
pub end: sk_buff_data_t,
pub head: *mut core::ffi::c_uchar,
pub data: *mut core::ffi::c_uchar,
pub truesize: core::ffi::c_uint,
pub users: refcount_t,
pub extensions: *mut skb_ext,
}
#[repr(C)]
pub struct sk_buff__bindgen_ty_4 {
pub __bindgen_anon_1: __BindgenUnionField<sk_buff__bindgen_ty_4__bindgen_ty_1>, // one of the values is here
pub headers: __BindgenUnionField<sk_buff__bindgen_ty_4__bindgen_ty_2>, // and the other one is here
pub bindgen_union_field: [u32; 14usize],
}
#[repr(C)]
pub struct sk_buff__bindgen_ty_4__bindgen_ty_1 {
pub __pkt_type_offset: __IncompleteArrayField<__u8>,
pub _bitfield_align_1: [u8; 0],
pub _bitfield_1: __BindgenBitfieldUnit<[u8; 1usize]>,
pub __mono_tc_offset: __IncompleteArrayField<__u8>,
pub _bitfield_align_2: [u8; 0],
pub _bitfield_2: __BindgenBitfieldUnit<[u8; 3usize]>,
pub tc_index: __u16,
pub alloc_cpu: u16_,
pub __bindgen_anon_1: sk_buff__bindgen_ty_4__bindgen_ty_1__bindgen_ty_1,
pub priority: __u32,
pub skb_iif: core::ffi::c_int,
pub hash: __u32,
pub __bindgen_anon_2: sk_buff__bindgen_ty_4__bindgen_ty_1__bindgen_ty_2,
pub __bindgen_anon_3: sk_buff__bindgen_ty_4__bindgen_ty_1__bindgen_ty_3,
pub secmark: __u32,
pub __bindgen_anon_4: sk_buff__bindgen_ty_4__bindgen_ty_1__bindgen_ty_4,
pub __bindgen_anon_5: sk_buff__bindgen_ty_4__bindgen_ty_1__bindgen_ty_5,
pub inner_transport_header: __u16,
pub inner_network_header: __u16,
pub inner_mac_header: __u16,
pub protocol: __be16,
pub transport_header: __u16,
pub network_header: __u16, // Ladies and gentlemen, we got him
pub mac_header: __u16,
}
#[repr(C)]
pub struct sk_buff__bindgen_ty_4__bindgen_ty_2 {
pub __pkt_type_offset: __IncompleteArrayField<__u8>,
pub _bitfield_align_1: [u8; 0],
pub _bitfield_1: __BindgenBitfieldUnit<[u8; 1usize]>,
pub __mono_tc_offset: __IncompleteArrayField<__u8>,
pub _bitfield_align_2: [u8; 0],
pub _bitfield_2: __BindgenBitfieldUnit<[u8; 3usize]>,
pub tc_index: __u16,
pub alloc_cpu: u16_,
pub __bindgen_anon_1: sk_buff__bindgen_ty_4__bindgen_ty_2__bindgen_ty_1,
pub priority: __u32,
pub skb_iif: core::ffi::c_int,
pub hash: __u32,
pub __bindgen_anon_2: sk_buff__bindgen_ty_4__bindgen_ty_2__bindgen_ty_2,
pub __bindgen_anon_3: sk_buff__bindgen_ty_4__bindgen_ty_2__bindgen_ty_3,
pub secmark: __u32,
pub __bindgen_anon_4: sk_buff__bindgen_ty_4__bindgen_ty_2__bindgen_ty_4,
pub __bindgen_anon_5: sk_buff__bindgen_ty_4__bindgen_ty_2__bindgen_ty_5,
pub inner_transport_header: __u16,
pub inner_network_header: __u16,
pub inner_mac_header: __u16,
pub protocol: __be16,
pub transport_header: __u16,
pub network_header: __u16, // And here it is once again
pub mac_header: __u16,
}The structure I was interested in is the __u16 network_header. At the end of the day I was able to get the value (and it seems to be correct) from both places.
I think that this is a bug, since the original structure had the value as the regular field.