linux清理缓存cache_udp缓冲区满了,数据是否会丢失

struct sk_buff { /* These two members must be first. */ struct sk_buff *next;-------------有没有人想过为啥不用内核标准的list来，而是单独两个成员？如果你有好的想法，可以跟我讨论。 struct sk_buff *prev; #ifdef __GENKSYMS__ ktime_t tstamp; #else union { ktime_t tstamp; struct skb_mstamp skb_mstamp; }; #endif struct sock *sk; struct net_device *dev; /* * 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);------------------------------------这个可以看很多private的处理 unsigned long _skb_refdst; #ifdef CONFIG_XFRM struct sec_path *sp; #endif unsigned int len, data_len; __u16 mac_len, hdr_len; union { __wsum csum; struct { __u16 csum_start; __u16 csum_offset; }; }; __u32 priority; kmemcheck_bitfield_begin(flags1); __u8 RH_KABI_RENAME(local_df, ignore_df):1, cloned:1, ip_summed:2, nohdr:1, nfctinfo:3; __u8 pkt_type:3, fclone:2, ipvs_property:1, peeked:1, nf_trace:1; kmemcheck_bitfield_end(flags1); __be16 protocol; void (*destructor)(struct sk_buff *skb); #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE) struct nf_conntrack *nfct; #endif #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) struct nf_bridge_info *nf_bridge; #endif /* fields enclosed in headers_start/headers_end are copied * using a single memcpy() in __copy_skb_header() */ /* private: */ RH_KABI_EXTEND(__u32 headers_start[0]) /* public: */ int skb_iif; RH_KABI_REPLACE(__u32 rxhash, __u32 hash) __be16 vlan_proto; __u16 vlan_tci; #ifdef CONFIG_NET_SCHED __u16 tc_index; /* traffic control index */ #ifdef CONFIG_NET_CLS_ACT __u16 tc_verd; /* traffic control verdict */ #endif #endif __u16 queue_mapping; kmemcheck_bitfield_begin(flags2); #ifdef CONFIG_IPV6_NDISC_NODETYPE __u8 ndisc_nodetype:2; #endif __u8 pfmemalloc:1; __u8 ooo_okay:1; __u8 RH_KABI_RENAME(l4_rxhash, l4_hash):1; __u8 wifi_acked_valid:1; __u8 wifi_acked:1; __u8 no_fcs:1; __u8 head_frag:1; /* Indicates the inner headers are valid in the skbuff. */ __u8 encapsulation:1; RH_KABI_EXTEND(__u8 encap_hdr_csum:1)-----------------------这个使用在我之前一篇博客中有描述。 RH_KABI_EXTEND(__u8 csum_valid:1) RH_KABI_EXTEND(__u8 csum_complete_sw:1) RH_KABI_EXTEND(__u8 xmit_more:1) RH_KABI_EXTEND(__u8 inner_protocol_type:1) RH_KABI_EXTEND(__u8 remcsum_offload:1) /* 0/2 bit hole (depending on ndisc_nodetype presence) */ kmemcheck_bitfield_end(flags2); #if defined CONFIG_NET_DMA_RH_KABI || defined CONFIG_NET_RX_BUSY_POLL || defined CONFIG_XPS union { unsigned int napi_id; RH_KABI_EXTEND(unsigned int sender_cpu) RH_KABI_DEPRECATE(dma_cookie_t, dma_cookie) }; #endif #ifdef CONFIG_NETWORK_SECMARK __u32 secmark; #endif union { __u32 mark; __u32 dropcount; __u32 reserved_tailroom; }; #ifdef __GENKSYMS__ __be16 inner_protocol; #else union { __be16 inner_protocol; __u8 inner_ipproto; }; #endif __u16 inner_transport_header; __u16 inner_network_header; __u16 inner_mac_header; __u16 transport_header; __u16 network_header; __u16 mac_header; RH_KABI_EXTEND(kmemcheck_bitfield_begin(flags3)) RH_KABI_EXTEND(__u8 csum_level:2) RH_KABI_EXTEND(__u8 rh_csum_pad:1) RH_KABI_EXTEND(__u8 csum_bad:1) RH_KABI_EXTEND(__u8 offload_fwd_mark:1) RH_KABI_EXTEND(__u8 sw_hash:1) RH_KABI_EXTEND(__u8 csum_not_inet:1) RH_KABI_EXTEND(__u8 dst_pending_confirm:1) /* 8 bit hole */ RH_KABI_EXTEND(kmemcheck_bitfield_end(flags3)) /* private: */ RH_KABI_EXTEND(__u32 headers_end[0]) /* public: */ /* RHEL SPECIFIC * * The following padding has been inserted before ABI freeze to * allow extending the structure while preserve ABI. Feel free * to replace reserved slots with required structure field * additions of your backport, eventually moving the replaced slot * before headers_end, if it need to be copied by __copy_skb_header() */ u32 rh_reserved1; u32 rh_reserved2; u32 rh_reserved3; u32 rh_reserved4; /* 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; atomic_t users; };