snmp(简单网络管理协议)中的proc代码的分析。

lvan_linux

1:简单网络管理(snmp):是指管理指定协议的网络,如ip协议、icmp协议等,其中会将收到的ip数据存放到指定的文件夹中。
2:关于内核中的代码他的执行和平时写的c代码执行是有些不同的,(我的理解,我们写一些简单的内核模块时、是将一些代码写成一个小的工具,然后执行这个小的工具)。

            
            内核中使用__init ipv6_misc_proc_init这个函数函数执行这个我们写的函数,使用ipv6_misc_proc_exit退出这个程序。
            同时内核中使用insmode安装内核模块,将内核模块安装到内核中。
            
            

3:接下来说关于snmp的源码(我这里是在Linux内核4.1.51中寻找的源码)。

            
            首先我们先将proc.c文件内容中的各种函数粘贴到这里,我这里逐一解释函数的作用。
            //将套接口的状态显示到文件中。
            static int sockstat6_seq_show(struct seq_file *seq, void *v);
            //打开保存套接口状态的文件。
            static int sockstat6_seq_open(struct inode *inode, struct file *file);
            //将icmp6的数据显示到保存icmp6的文件中,可以在Linux系统/proc/net目录下找到。
            static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, atomic_long_t *smib);
            //将snmp6的一些项显示到文件中,下面两个函数就是这个功能。
            static void snmp6_seq_show_item(struct seq_file *seq, void __percpu *pcpumib,atomic_long_t *smib,    const struct snmp_mib *itemlist);
            static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu *mib,   const struct snmp_mib *itemlist, size_t syncpoff);
            //将各种信息调用上面两个函数分别显示到文件中
            static int snmp6_seq_show(struct seq_file *seq, void *v);
            //这是将打开要显示的snmp6文件。
            static int snmp6_seq_open(struct inode *inode, struct file *file);
            //dev文件的打开,我猜测是类似/proc/net/dev文件。
            static int snmp6_dev_seq_show(struct seq_file *seq, void *v);
            static int snmp6_dev_seq_open(struct inode *inode, struct file *file);
            //下面六个文件前两个分别是snmp6文件的注册和解注册,中间两个是ipv6文件的注册和解注册,最后两个是程序的入口。
            int snmp6_register_dev(struct inet6_dev *idev);
            int snmp6_unregister_dev(struct inet6_dev *idev);
            static int __net_init ipv6_proc_init_net(struct net *net);
            static void __net_exit ipv6_proc_exit_net(struct net *net);
            int __init ipv6_misc_proc_init(void);
            void ipv6_misc_proc_exit(void);
            
            第二部分:接下来我们说明一下此文档的数据结构。
            下面这部分是其中一部分数据结构,snmp_mib是一个结构体(结构体中内容为名字和保存位置的行数。SNMP_MIB_ITEM是结构体内容初始化函数。
            如果想看结构体数组中的具体内容,我们可以参考对应的rfc文档。如下面第一个黑体字。有些没有写对应rfc文档的根据名字就可以知道是干什么用的了。
            static const struct snmp_mib snmp6_ipstats_list[] = {
            /* ipv6 mib according to** RFC 2465** */
                SNMP_MIB_ITEM("Ip6InReceives", IPSTATS_MIB_INPKTS),
                SNMP_MIB_ITEM("Ip6InHdrErrors", IPSTATS_MIB_INHDRERRORS),
                SNMP_MIB_ITEM("Ip6InTooBigErrors", IPSTATS_MIB_INTOOBIGERRORS),
                SNMP_MIB_ITEM("Ip6InNoRoutes", IPSTATS_MIB_INNOROUTES),
                SNMP_MIB_ITEM("Ip6InAddrErrors", IPSTATS_MIB_INADDRERRORS),
                SNMP_MIB_ITEM("Ip6InUnknownProtos", IPSTATS_MIB_INUNKNOWNPROTOS),
                SNMP_MIB_ITEM("Ip6InTruncatedPkts", IPSTATS_MIB_INTRUNCATEDPKTS),
                SNMP_MIB_ITEM("Ip6InDiscards", IPSTATS_MIB_INDISCARDS),
                SNMP_MIB_ITEM("Ip6InDelivers", IPSTATS_MIB_INDELIVERS),
                SNMP_MIB_ITEM("Ip6OutForwDatagrams", IPSTATS_MIB_OUTFORWDATAGRAMS),
                SNMP_MIB_ITEM("Ip6OutRequests", IPSTATS_MIB_OUTPKTS),
                SNMP_MIB_ITEM("Ip6OutDiscards", IPSTATS_MIB_OUTDISCARDS),
                SNMP_MIB_ITEM("Ip6OutNoRoutes", IPSTATS_MIB_OUTNOROUTES),
                SNMP_MIB_ITEM("Ip6ReasmTimeout", IPSTATS_MIB_REASMTIMEOUT),
                SNMP_MIB_ITEM("Ip6ReasmReqds", IPSTATS_MIB_REASMREQDS),
                SNMP_MIB_ITEM("Ip6ReasmOKs", IPSTATS_MIB_REASMOKS),
                SNMP_MIB_ITEM("Ip6ReasmFails", IPSTATS_MIB_REASMFAILS),
                SNMP_MIB_ITEM("Ip6FragOKs", IPSTATS_MIB_FRAGOKS),
                SNMP_MIB_ITEM("Ip6FragFails", IPSTATS_MIB_FRAGFAILS),
                SNMP_MIB_ITEM("Ip6FragCreates", IPSTATS_MIB_FRAGCREATES),
                SNMP_MIB_ITEM("Ip6InMcastPkts", IPSTATS_MIB_INMCASTPKTS),
                SNMP_MIB_ITEM("Ip6OutMcastPkts", IPSTATS_MIB_OUTMCASTPKTS),
                SNMP_MIB_ITEM("Ip6InOctets", IPSTATS_MIB_INOCTETS),
                SNMP_MIB_ITEM("Ip6OutOctets", IPSTATS_MIB_OUTOCTETS),
                SNMP_MIB_ITEM("Ip6InMcastOctets", IPSTATS_MIB_INMCASTOCTETS),
                SNMP_MIB_ITEM("Ip6OutMcastOctets", IPSTATS_MIB_OUTMCASTOCTETS),
                SNMP_MIB_ITEM("Ip6InBcastOctets", IPSTATS_MIB_INBCASTOCTETS),
                SNMP_MIB_ITEM("Ip6OutBcastOctets", IPSTATS_MIB_OUTBCASTOCTETS),
                /* IPSTATS_MIB_CSUMERRORS is not relevant in IPv6 (no checksum) */
                SNMP_MIB_ITEM("Ip6InNoECTPkts", IPSTATS_MIB_NOECTPKTS),
                SNMP_MIB_ITEM("Ip6InECT1Pkts", IPSTATS_MIB_ECT1PKTS),
                SNMP_MIB_ITEM("Ip6InECT0Pkts", IPSTATS_MIB_ECT0PKTS),
                SNMP_MIB_ITEM("Ip6InCEPkts", IPSTATS_MIB_CEPKTS),
                SNMP_MIB_SENTINEL
            };

            static const struct snmp_mib snmp6_icmp6_list[] = {
            /* icmpv6 mib according to RFC 2466 */
                SNMP_MIB_ITEM("Icmp6InMsgs", ICMP6_MIB_INMSGS),
                SNMP_MIB_ITEM("Icmp6InErrors", ICMP6_MIB_INERRORS),
                SNMP_MIB_ITEM("Icmp6OutMsgs", ICMP6_MIB_OUTMSGS),
                SNMP_MIB_ITEM("Icmp6OutErrors", ICMP6_MIB_OUTERRORS),
                SNMP_MIB_ITEM("Icmp6InCsumErrors", ICMP6_MIB_CSUMERRORS),
                SNMP_MIB_SENTINEL
            };

            /* RFC 4293 v6 ICMPMsgStatsTable; named items for RFC 2466 compatibility */
            static const char *const icmp6type2name[256] = {
                [ICMPV6_DEST_UNREACH] = "DestUnreachs",
                [ICMPV6_PKT_TOOBIG] = "PktTooBigs",
                [ICMPV6_TIME_EXCEED] = "TimeExcds",
                [ICMPV6_PARAMPROB] = "ParmProblems",
                [ICMPV6_ECHO_REQUEST] = "Echos",
                [ICMPV6_ECHO_REPLY] = "EchoReplies",
                [ICMPV6_MGM_QUERY] = "GroupMembQueries",
                [ICMPV6_MGM_REPORT] = "GroupMembResponses",
                [ICMPV6_MGM_REDUCTION] = "GroupMembReductions",
                [ICMPV6_MLD2_REPORT] = "MLDv2Reports",
                [NDISC_ROUTER_ADVERTISEMENT] = "RouterAdvertisements",
                [NDISC_ROUTER_SOLICITATION] = "RouterSolicits",
                [NDISC_NEIGHBOUR_ADVERTISEMENT] = "NeighborAdvertisements",
                [NDISC_NEIGHBOUR_SOLICITATION] = "NeighborSolicits",
                [NDISC_REDIRECT] = "Redirects",
            };


            static const struct snmp_mib snmp6_udp6_list[] = {
                SNMP_MIB_ITEM("Udp6InDatagrams", UDP_MIB_INDATAGRAMS),
                SNMP_MIB_ITEM("Udp6NoPorts", UDP_MIB_NOPORTS),
                SNMP_MIB_ITEM("Udp6InErrors", UDP_MIB_INERRORS),
                SNMP_MIB_ITEM("Udp6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
                SNMP_MIB_ITEM("Udp6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
                SNMP_MIB_ITEM("Udp6SndbufErrors", UDP_MIB_SNDBUFERRORS),
                SNMP_MIB_ITEM("Udp6InCsumErrors", UDP_MIB_CSUMERRORS),
                SNMP_MIB_ITEM("Udp6IgnoredMulti", UDP_MIB_IGNOREDMULTI),
                SNMP_MIB_SENTINEL
            };

            static const struct snmp_mib snmp6_udplite6_list[] = {
                SNMP_MIB_ITEM("UdpLite6InDatagrams", UDP_MIB_INDATAGRAMS),
                SNMP_MIB_ITEM("UdpLite6NoPorts", UDP_MIB_NOPORTS),
                SNMP_MIB_ITEM("UdpLite6InErrors", UDP_MIB_INERRORS),
                SNMP_MIB_ITEM("UdpLite6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
                SNMP_MIB_ITEM("UdpLite6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
                SNMP_MIB_ITEM("UdpLite6SndbufErrors", UDP_MIB_SNDBUFERRORS),
                SNMP_MIB_ITEM("UdpLite6InCsumErrors", UDP_MIB_CSUMERRORS),
                SNMP_MIB_SENTINEL
            };
            接下来这部分结构体如下所示。他是定位到文件的指定位置。
            static const struct file_operations snmp6_seq_fops = {
            .owner     = THIS_MODULE,
            .open     = snmp6_seq_open,
            .read     = seq_read,
            .llseek     = seq_lseek,
            .release = single_release_net,
        };
        
        
        第三部分:这部分我将源代码贴上去,并且将进入函数执行流程分析一边,对应的分析退出函数的流程。
        /*
         * INET        An implementation of the TCP/IP protocol suite for the LINUX
         *        operating system.  INET is implemented using the  BSD Socket
         *        interface as the means of communication with the user level.
         *
         *        This file implements the various access functions for the
         *        PROC file system.  This is very similar to the IPv4 version,
         *        except it reports the sockets in the INET6 address family.
         *
         * Authors:    David S. Miller (davem@caip.rutgers.edu)
         *        YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
         *
         *        This program is free software; you can redistribute it and/or
         *        modify it under the terms of the GNU General Public License
         *        as published by the Free Software Foundation; either version
         *        2 of the License, or (at your option) any later version.
         */
        #include <linux/socket.h>
        #include <linux/net.h>
        #include <linux/ipv6.h>
        #include <linux/proc_fs.h>
        #include <linux/seq_file.h>
        #include <linux/stddef.h>
        #include <linux/export.h>
        #include <net/net_namespace.h>
        #include <net/ip.h>
        #include <net/sock.h>
        #include <net/tcp.h>
        #include <net/udp.h>
        #include <net/transp_v6.h>
        #include <net/ipv6.h>

        static int sockstat6_seq_show(struct seq_file *seq, void *v)
        {
            struct net *net = seq->private;
            unsigned int frag_mem = ip6_frag_mem(net);

            seq_printf(seq, "TCP6: inuse %d\n",
                             sock_prot_inuse_get(net, &tcpv6_prot));
            seq_printf(seq, "UDP6: inuse %d\n",
                             sock_prot_inuse_get(net, &udpv6_prot));
            seq_printf(seq, "UDPLITE6: inuse %d\n",
                    sock_prot_inuse_get(net, &udplitev6_prot));
            seq_printf(seq, "RAW6: inuse %d\n",
                             sock_prot_inuse_get(net, &rawv6_prot));
            seq_printf(seq, "FRAG6: inuse %u memory %u\n", !!frag_mem, frag_mem);
            return 0;
        }

        static int sockstat6_seq_open(struct inode *inode, struct file *file)
        {
            return single_open_net(inode, file, sockstat6_seq_show);
        }

        static const struct file_operations sockstat6_seq_fops = {
            .owner     = THIS_MODULE,
            .open     = sockstat6_seq_open,
            .read     = seq_read,
            .llseek     = seq_lseek,
            .release = single_release_net,
        };

        static const struct snmp_mib snmp6_ipstats_list[] = {
        /* ipv6 mib according to RFC 2465 */
            SNMP_MIB_ITEM("Ip6InReceives", IPSTATS_MIB_INPKTS),
            SNMP_MIB_ITEM("Ip6InHdrErrors", IPSTATS_MIB_INHDRERRORS),
            SNMP_MIB_ITEM("Ip6InTooBigErrors", IPSTATS_MIB_INTOOBIGERRORS),
            SNMP_MIB_ITEM("Ip6InNoRoutes", IPSTATS_MIB_INNOROUTES),
            SNMP_MIB_ITEM("Ip6InAddrErrors", IPSTATS_MIB_INADDRERRORS),
            SNMP_MIB_ITEM("Ip6InUnknownProtos", IPSTATS_MIB_INUNKNOWNPROTOS),
            SNMP_MIB_ITEM("Ip6InTruncatedPkts", IPSTATS_MIB_INTRUNCATEDPKTS),
            SNMP_MIB_ITEM("Ip6InDiscards", IPSTATS_MIB_INDISCARDS),
            SNMP_MIB_ITEM("Ip6InDelivers", IPSTATS_MIB_INDELIVERS),
            SNMP_MIB_ITEM("Ip6OutForwDatagrams", IPSTATS_MIB_OUTFORWDATAGRAMS),
            SNMP_MIB_ITEM("Ip6OutRequests", IPSTATS_MIB_OUTPKTS),
            SNMP_MIB_ITEM("Ip6OutDiscards", IPSTATS_MIB_OUTDISCARDS),
            SNMP_MIB_ITEM("Ip6OutNoRoutes", IPSTATS_MIB_OUTNOROUTES),
            SNMP_MIB_ITEM("Ip6ReasmTimeout", IPSTATS_MIB_REASMTIMEOUT),
            SNMP_MIB_ITEM("Ip6ReasmReqds", IPSTATS_MIB_REASMREQDS),
            SNMP_MIB_ITEM("Ip6ReasmOKs", IPSTATS_MIB_REASMOKS),
            SNMP_MIB_ITEM("Ip6ReasmFails", IPSTATS_MIB_REASMFAILS),
            SNMP_MIB_ITEM("Ip6FragOKs", IPSTATS_MIB_FRAGOKS),
            SNMP_MIB_ITEM("Ip6FragFails", IPSTATS_MIB_FRAGFAILS),
            SNMP_MIB_ITEM("Ip6FragCreates", IPSTATS_MIB_FRAGCREATES),
            SNMP_MIB_ITEM("Ip6InMcastPkts", IPSTATS_MIB_INMCASTPKTS),
            SNMP_MIB_ITEM("Ip6OutMcastPkts", IPSTATS_MIB_OUTMCASTPKTS),
            SNMP_MIB_ITEM("Ip6InOctets", IPSTATS_MIB_INOCTETS),
            SNMP_MIB_ITEM("Ip6OutOctets", IPSTATS_MIB_OUTOCTETS),
            SNMP_MIB_ITEM("Ip6InMcastOctets", IPSTATS_MIB_INMCASTOCTETS),
            SNMP_MIB_ITEM("Ip6OutMcastOctets", IPSTATS_MIB_OUTMCASTOCTETS),
            SNMP_MIB_ITEM("Ip6InBcastOctets", IPSTATS_MIB_INBCASTOCTETS),
            SNMP_MIB_ITEM("Ip6OutBcastOctets", IPSTATS_MIB_OUTBCASTOCTETS),
            /* IPSTATS_MIB_CSUMERRORS is not relevant in IPv6 (no checksum) */
            SNMP_MIB_ITEM("Ip6InNoECTPkts", IPSTATS_MIB_NOECTPKTS),
            SNMP_MIB_ITEM("Ip6InECT1Pkts", IPSTATS_MIB_ECT1PKTS),
            SNMP_MIB_ITEM("Ip6InECT0Pkts", IPSTATS_MIB_ECT0PKTS),
            SNMP_MIB_ITEM("Ip6InCEPkts", IPSTATS_MIB_CEPKTS),
            SNMP_MIB_SENTINEL
        };

        static const struct snmp_mib snmp6_icmp6_list[] = {
        /* icmpv6 mib according to RFC 2466 */
            SNMP_MIB_ITEM("Icmp6InMsgs", ICMP6_MIB_INMSGS),
            SNMP_MIB_ITEM("Icmp6InErrors", ICMP6_MIB_INERRORS),
            SNMP_MIB_ITEM("Icmp6OutMsgs", ICMP6_MIB_OUTMSGS),
            SNMP_MIB_ITEM("Icmp6OutErrors", ICMP6_MIB_OUTERRORS),
            SNMP_MIB_ITEM("Icmp6InCsumErrors", ICMP6_MIB_CSUMERRORS),
            SNMP_MIB_SENTINEL
        };

        /* RFC 4293 v6 ICMPMsgStatsTable; named items for RFC 2466 compatibility */
        static const char *const icmp6type2name[256] = {
            [ICMPV6_DEST_UNREACH] = "DestUnreachs",
            [ICMPV6_PKT_TOOBIG] = "PktTooBigs",
            [ICMPV6_TIME_EXCEED] = "TimeExcds",
            [ICMPV6_PARAMPROB] = "ParmProblems",
            [ICMPV6_ECHO_REQUEST] = "Echos",
            [ICMPV6_ECHO_REPLY] = "EchoReplies",
            [ICMPV6_MGM_QUERY] = "GroupMembQueries",
            [ICMPV6_MGM_REPORT] = "GroupMembResponses",
            [ICMPV6_MGM_REDUCTION] = "GroupMembReductions",
            [ICMPV6_MLD2_REPORT] = "MLDv2Reports",
            [NDISC_ROUTER_ADVERTISEMENT] = "RouterAdvertisements",
            [NDISC_ROUTER_SOLICITATION] = "RouterSolicits",
            [NDISC_NEIGHBOUR_ADVERTISEMENT] = "NeighborAdvertisements",
            [NDISC_NEIGHBOUR_SOLICITATION] = "NeighborSolicits",
            [NDISC_REDIRECT] = "Redirects",
        };


        static const struct snmp_mib snmp6_udp6_list[] = {
            SNMP_MIB_ITEM("Udp6InDatagrams", UDP_MIB_INDATAGRAMS),
            SNMP_MIB_ITEM("Udp6NoPorts", UDP_MIB_NOPORTS),
            SNMP_MIB_ITEM("Udp6InErrors", UDP_MIB_INERRORS),
            SNMP_MIB_ITEM("Udp6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
            SNMP_MIB_ITEM("Udp6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
            SNMP_MIB_ITEM("Udp6SndbufErrors", UDP_MIB_SNDBUFERRORS),
            SNMP_MIB_ITEM("Udp6InCsumErrors", UDP_MIB_CSUMERRORS),
            SNMP_MIB_ITEM("Udp6IgnoredMulti", UDP_MIB_IGNOREDMULTI),
            SNMP_MIB_SENTINEL
        };

        static const struct snmp_mib snmp6_udplite6_list[] = {
            SNMP_MIB_ITEM("UdpLite6InDatagrams", UDP_MIB_INDATAGRAMS),
            SNMP_MIB_ITEM("UdpLite6NoPorts", UDP_MIB_NOPORTS),
            SNMP_MIB_ITEM("UdpLite6InErrors", UDP_MIB_INERRORS),
            SNMP_MIB_ITEM("UdpLite6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
            SNMP_MIB_ITEM("UdpLite6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
            SNMP_MIB_ITEM("UdpLite6SndbufErrors", UDP_MIB_SNDBUFERRORS),
            SNMP_MIB_ITEM("UdpLite6InCsumErrors", UDP_MIB_CSUMERRORS),
            SNMP_MIB_SENTINEL
        };

        static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, atomic_long_t *smib)
        {
            char name[32];
            int i;

            /* print by name -- deprecated items */
            for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
                int icmptype;
                const char *p;

                icmptype = i & 0xff;
                p = icmp6type2name[icmptype];
                if (!p)    /* don't print un-named types here */
                    continue;
                snprintf(name, sizeof(name), "Icmp6%s%s",
                    i & 0x100 ? "Out" : "In", p);
                seq_printf(seq, "%-32s\t%lu\n", name,
                         atomic_long_read(smib + i));
            }

            /* print by number (nonzero only) - ICMPMsgStat format */
            for (i = 0; i < ICMP6MSG_MIB_MAX; i++) {
                unsigned long val;

                val = atomic_long_read(smib + i);
                if (!val)
                    continue;
                snprintf(name, sizeof(name), "Icmp6%sType%u",
                    i & 0x100 ?  "Out" : "In", i & 0xff);
                seq_printf(seq, "%-32s\t%lu\n", name, val);
            }
        }

        /* can be called either with percpu mib (pcpumib != NULL),
         * or shared one (smib != NULL)
         */
        static void snmp6_seq_show_item(struct seq_file *seq, void __percpu *pcpumib,
                        atomic_long_t *smib,
                        const struct snmp_mib *itemlist)
        {
            int i;
            unsigned long val;

            for (i = 0; itemlist[i].name; i++) {
                val = pcpumib ?
                    snmp_fold_field(pcpumib, itemlist[i].entry) :
                    atomic_long_read(smib + itemlist[i].entry);
                seq_printf(seq, "%-32s\t%lu\n", itemlist[i].name, val);
            }
        }

        static void snmp6_seq_show_item64(struct seq_file *seq, void __percpu *mib,
                            const struct snmp_mib *itemlist, size_t syncpoff)
        {
            int i;

            for (i = 0; itemlist[i].name; i++)
                seq_printf(seq, "%-32s\t%llu\n", itemlist[i].name,
                         snmp_fold_field64(mib, itemlist[i].entry, syncpoff));
        }

        static int snmp6_seq_show(struct seq_file *seq, void *v)
        {
            struct net *net = (struct net *)seq->private;

            snmp6_seq_show_item64(seq, net->mib.ipv6_statistics,
                            snmp6_ipstats_list, offsetof(struct ipstats_mib, syncp));
            snmp6_seq_show_item(seq, net->mib.icmpv6_statistics,
                            NULL, snmp6_icmp6_list);
            snmp6_seq_show_icmpv6msg(seq, net->mib.icmpv6msg_statistics->mibs);
            snmp6_seq_show_item(seq, net->mib.udp_stats_in6,
                            NULL, snmp6_udp6_list);
            snmp6_seq_show_item(seq, net->mib.udplite_stats_in6,
                            NULL, snmp6_udplite6_list);
            return 0;
        }

        static int snmp6_seq_open(struct inode *inode, struct file *file)
        {
            return single_open_net(inode, file, snmp6_seq_show);
        }

        static const struct file_operations snmp6_seq_fops = {
            .owner     = THIS_MODULE,
            .open     = snmp6_seq_open,
            .read     = seq_read,
            .llseek     = seq_lseek,
            .release = single_release_net,
        };

        static int snmp6_dev_seq_show(struct seq_file *seq, void *v)
        {
            struct inet6_dev *idev = (struct inet6_dev *)seq->private;

            seq_printf(seq, "%-32s\t%u\n", "ifIndex", idev->dev->ifindex);
            snmp6_seq_show_item64(seq, idev->stats.ipv6,
                            snmp6_ipstats_list, offsetof(struct ipstats_mib, syncp));
            snmp6_seq_show_item(seq, NULL, idev->stats.icmpv6dev->mibs,
                            snmp6_icmp6_list);
            snmp6_seq_show_icmpv6msg(seq, idev->stats.icmpv6msgdev->mibs);
            return 0;
        }

        static int snmp6_dev_seq_open(struct inode *inode, struct file *file)
        {
            return single_open(file, snmp6_dev_seq_show, PDE_DATA(inode));
        }

        static const struct file_operations snmp6_dev_seq_fops = {
            .owner     = THIS_MODULE,
            .open     = snmp6_dev_seq_open,
            .read     = seq_read,
            .llseek     = seq_lseek,
            .release = single_release,
        };

        int snmp6_register_dev(struct inet6_dev *idev)
        {
            struct proc_dir_entry *p;
            struct net *net;

            if (!idev || !idev->dev)
                return -EINVAL;

            net = dev_net(idev->dev);
            if (!net->mib.proc_net_devsnmp6)
                return -ENOENT;

            p = proc_create_data(idev->dev->name, S_IRUGO,
                             net->mib.proc_net_devsnmp6,
                             &snmp6_dev_seq_fops, idev);
            if (!p)
                return -ENOMEM;

            idev->stats.proc_dir_entry = p;
            return 0;
        }

        int snmp6_unregister_dev(struct inet6_dev *idev)
        {
            struct net *net = dev_net(idev->dev);
            if (!net->mib.proc_net_devsnmp6)
                return -ENOENT;
            if (!idev->stats.proc_dir_entry)
                return -EINVAL;
            proc_remove(idev->stats.proc_dir_entry);
            idev->stats.proc_dir_entry = NULL;
            return 0;
        }

        static int __net_init ipv6_proc_init_net(struct net *net)
        {
            if (!proc_create("sockstat6", S_IRUGO, net->proc_net,
                     &sockstat6_seq_fops))
                return -ENOMEM;

            if (!proc_create("snmp6", S_IRUGO, net->proc_net, &snmp6_seq_fops))
                goto proc_snmp6_fail;

            net->mib.proc_net_devsnmp6 = proc_mkdir("dev_snmp6", net->proc_net);
            if (!net->mib.proc_net_devsnmp6)
                goto proc_dev_snmp6_fail;
            return 0;

        proc_dev_snmp6_fail:
            remove_proc_entry("snmp6", net->proc_net);
        proc_snmp6_fail:
            remove_proc_entry("sockstat6", net->proc_net);
            return -ENOMEM;
        }

        static void __net_exit ipv6_proc_exit_net(struct net *net)
        {
            remove_proc_entry("sockstat6", net->proc_net);
            remove_proc_entry("dev_snmp6", net->proc_net);
            remove_proc_entry("snmp6", net->proc_net);
        }

        static struct pernet_operations ipv6_proc_ops = {
            .init = ipv6_proc_init_net,
            .exit = ipv6_proc_exit_net,
        };

        int __init ipv6_misc_proc_init(void)
        {
            return register_pernet_subsys(&ipv6_proc_ops);
        }

        void ipv6_misc_proc_exit(void)
        {
            unregister_pernet_subsys(&ipv6_proc_ops);
        }
        
                是u先是从从ipv6_misc_proc_init函数中调用函数进行注册,也就是接下来执行ipv6_proc_init_net这个函数。在这个函数中分别进行创建对应的内容,然后执行如if (!proc_create("sockstat6", S_IRUGO, net->proc_net, &sockstat6_seq_fops))中的sockstat6_seq_fops部分中的sockstat6_seq_open,之后执行single_open_net(inode, file, sockstat6_seq_show);中的sockstat6_seq_show函数,最后就是将各种数据显示到对应的文件中去了。
                
            关于snmp文件可以参考rfc文档,


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