Linux skbuff注釋筆記

標籤：

SKB結構定義   /usr/src/linux/include/linux/skbuff.h

sk_buff_head：

1 struct sk_buff_head {            //SKB的頭結點2     /* These two members must be first. */3     struct sk_buff    *next;     4     struct sk_buff    *prev;5 6     __u32        qlen;           //隊列長度7     spinlock_t    lock;          //自旋鎖8 };

 

sk_buff：

/**  *    struct sk_buff - socket buffer *    @next: Next buffer in list *    @prev: Previous buffer in list *    @sk: Socket we are owned by *    @tstamp: Time we arrived *    @dev: Device we arrived on/are leaving by *    @input_dev: Device we arrived on *    @h: Transport layer header *    @nh: Network layer header *    @mac: Link layer header *    @dst: destination entry *    @sp: the security path, used for xfrm *    @cb: Control buffer. Free for use by every layer. Put private vars here *    @len: Length of actual data *    @data_len: Data length *    @mac_len: Length of link layer header *    @csum: Checksum *    @local_df: allow local fragmentation *    @cloned: Head may be cloned (check refcnt to be sure) *    @nohdr: Payload reference only, must not modify header *    @pkt_type: Packet class *    @fclone: skbuff clone status *    @ip_summed: Driver fed us an IP checksum *    @priority: Packet queueing priority *    @users: User count - see {datagram,tcp}.c *    @protocol: Packet protocol from driver *    @truesize: Buffer size  *    @head: Head of buffer *    @data: Data head pointer *    @tail: Tail pointer *    @end: End pointer *    @destructor: Destruct function *    @mark: Generic packet mark *    @nfct: Associated connection, if any *    @ipvs_property: skbuff is owned by ipvs *    @nfctinfo: Relationship of this skb to the connection *    @nfct_reasm: netfilter conntrack re-assembly pointer *    @nf_bridge: Saved data about a bridged frame - see br_netfilter.c *    @tc_index: Traffic control index *    @tc_verd: traffic control verdict *    @dma_cookie: a cookie to one of several possible DMA operations *        done by skb DMA functions *    @secmark: security marking */struct sk_buff {    /* These two members must be first. */    struct sk_buff        *next;    struct sk_buff        *prev;    struct sock        *sk;              //宿主傳輸控制塊，本地發送或本地接收時有效，轉寄時為空白    struct skb_timeval    tstamp;        //時間戳記    struct net_device    *dev;           //網路裝置指標    struct net_device    *input_dev;     //接收報文的原始網路裝置，包為本地產生時為空白，用於流量控制    union {                              //指向四層協議首部，包含的資料結構表示在這一層上可以解析的協議        struct tcphdr    *th;        struct udphdr    *uh;        struct icmphdr    *icmph;        struct igmphdr    *igmph;        struct iphdr    *ipiph;        struct ipv6hdr    *ipv6h;        unsigned char    *raw;           // 用於初始化    } h;                                     union {                              //指向三層協議首部        struct iphdr    *iph;        struct ipv6hdr    *ipv6h;        struct arphdr    *arph;        unsigned char    *raw;    } nh;    union {                              //指向二層協議首部          unsigned char     *raw;    } mac;    struct  dst_entry    *dst;           //目的路由緩衝    struct    sec_path    *sp;           //IPSec協議用來跟蹤傳輸的資訊    /*     * 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];           //資訊控制區塊，儲存每層自己的私人資訊    unsigned int        len,          //資料部分長度，包含首部長度                data_len,             //SG類型和FRAGLIST類型彙總分散I/O儲存區中的資料長度                mac_len;              //資料連結層首部長度    union {        __wsum        csum;           //校正狀態為CHECKSUM_NONE時，存放所負載資料報的資料部分校正和        __u32        csum_offset;     //校正狀態為CHECKSUM_PARTIAL時，記錄傳輸層首部中的校正和欄位的位移    };    __u32            priority;        //發送或轉寄資料包QoS類別，    __u8            local_df:1,       //表示此SKB在本地允許分區                cloned:1,             //標記所屬SKB是否被複製                ip_summed:2,          //標記傳輸層校正和的狀態                nohdr:1,              //標識payload是否被單獨引用                nfctinfo:3;           //被防火牆使用    __u8            pkt_type:3,       //框架類型                fclone:2,             //當前複製狀態                ipvs_property:1;    __be16            protocol;       //鏈路層協議類型    void            (*destructor)(struct sk_buff *skb);           //解構函式指標，釋放時調用，沒有宿主傳輸控制塊時為空白#ifdef CONFIG_NETFILTER    struct nf_conntrack    *nfct;                                 //被防火牆使用#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)    struct sk_buff        *nfct_reasm;#endif#ifdef CONFIG_BRIDGE_NETFILTER    struct nf_bridge_info    *nf_bridge;                          //被防火牆使用#endif#endif /* CONFIG_NETFILTER */#ifdef CONFIG_NET_SCHED    __u16            tc_index;    /* traffic control index 流量控制*/#ifdef CONFIG_NET_CLS_ACT    __u16            tc_verd;    /* traffic control verdict */#endif#endif#ifdef CONFIG_NET_DMA    dma_cookie_t        dma_cookie;#endif#ifdef CONFIG_NETWORK_SECMARK    __u32            secmark;#endif    __u32            mark;    /* These elements must be at the end, see alloc_skb() for details.  */    unsigned int        truesize;        //緩衝區總長度    atomic_t        users;               //引用計數，標識有多少實體引用SKB，為零時釋放    unsigned char        *head,          //指向緩衝區頭                *data,                   //指向資料頭                *tail,                   //指向資料尾                *end;                    //指向緩衝區尾};

 

skb_shared_info：

 1 struct skb_shared_info {                  //儲存資料區塊的附加資訊 2     atomic_t    dataref;                  //引用計數器 3     unsigned short    nr_frags; 4     unsigned short    gso_size; 5     /* Warning: this field is not always filled in (UFO)! */ 6     unsigned short    gso_segs; 7     unsigned short  gso_type; 8     __be32          ip6_frag_id; 9     struct sk_buff    *frag_list;10     skb_frag_t    frags[MAX_SKB_FRAGS];11 };

 

Linux skbuff注釋筆記