1.概述
MIB 是 Management Information Base（管理信息库）的缩写。MIB 是一个标准化的数据库，用于存储与网络设备（如路由器、交换机、服务器等）相关的管理信息。它定义了设备上可被监控和管理的各种信息的结构，这些信息通常通过 SNMP（简单网络管理协议，Simple Network Management Protocol）进行访问和管理。
SNMP（Simple Network Management Protocol，简单网络管理协议）是一种用于管理和监控网络设备（如路由器、交换机、服务器、打印机等）状态的标准协议
查看mib的相关信息，可以看到是很多协议的一些统计信息，转发、丢包等数据。
2.源代码
文件路径：net/mptcp/mib.c
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/seq_file.h>
#include <net/ip.h>
#include <net/mptcp.h>
#include <net/snmp.h>
#include <net/net_namespace.h>
#include "mib.h"
static const struct snmp_mib mptcp_snmp_list[] = {
SNMP_MIB_ITEM("MPCapableSYNRX", MPTCP_MIB_MPCAPABLEPASSIVE),
SNMP_MIB_ITEM("MPCapableSYNTX", MPTCP_MIB_MPCAPABLEACTIVE),
SNMP_MIB_ITEM("MPCapableSYNACKRX", MPTCP_MIB_MPCAPABLEACTIVEACK),
SNMP_MIB_ITEM("MPCapableACKRX", MPTCP_MIB_MPCAPABLEPASSIVEACK),
SNMP_MIB_ITEM("MPCapableFallbackACK", MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK),
SNMP_MIB_ITEM("MPCapableFallbackSYNACK", MPTCP_MIB_MPCAPABLEACTIVEFALLBACK),
SNMP_MIB_ITEM("MPFallbackTokenInit", MPTCP_MIB_TOKENFALLBACKINIT),
SNMP_MIB_ITEM("MPTCPRetrans", MPTCP_MIB_RETRANSSEGS),
SNMP_MIB_ITEM("MPJoinNoTokenFound", MPTCP_MIB_JOINNOTOKEN),
SNMP_MIB_ITEM("MPJoinSynRx", MPTCP_MIB_JOINSYNRX),
SNMP_MIB_ITEM("MPJoinSynAckRx", MPTCP_MIB_JOINSYNACKRX),
SNMP_MIB_ITEM("MPJoinSynAckHMacFailure", MPTCP_MIB_JOINSYNACKMAC),
SNMP_MIB_ITEM("MPJoinAckRx", MPTCP_MIB_JOINACKRX),
SNMP_MIB_ITEM("MPJoinAckHMacFailure", MPTCP_MIB_JOINACKMAC),
SNMP_MIB_ITEM("DSSNotMatching", MPTCP_MIB_DSSNOMATCH),
SNMP_MIB_ITEM("InfiniteMapTx", MPTCP_MIB_INFINITEMAPTX),
SNMP_MIB_ITEM("InfiniteMapRx", MPTCP_MIB_INFINITEMAPRX),
SNMP_MIB_ITEM("DSSNoMatchTCP", MPTCP_MIB_DSSTCPMISMATCH),
SNMP_MIB_ITEM("DataCsumErr", MPTCP_MIB_DATACSUMERR),
SNMP_MIB_ITEM("OFOQueueTail", MPTCP_MIB_OFOQUEUETAIL),
SNMP_MIB_ITEM("OFOQueue", MPTCP_MIB_OFOQUEUE),
SNMP_MIB_ITEM("OFOMerge", MPTCP_MIB_OFOMERGE),
SNMP_MIB_ITEM("NoDSSInWindow", MPTCP_MIB_NODSSWINDOW),
SNMP_MIB_ITEM("DuplicateData", MPTCP_MIB_DUPDATA),
SNMP_MIB_ITEM("AddAddr", MPTCP_MIB_ADDADDR),
SNMP_MIB_ITEM("AddAddrTx", MPTCP_MIB_ADDADDRTX),
SNMP_MIB_ITEM("AddAddrTxDrop", MPTCP_MIB_ADDADDRTXDROP),
SNMP_MIB_ITEM("EchoAdd", MPTCP_MIB_ECHOADD),
SNMP_MIB_ITEM("EchoAddTx", MPTCP_MIB_ECHOADDTX),
SNMP_MIB_ITEM("EchoAddTxDrop", MPTCP_MIB_ECHOADDTXDROP),
SNMP_MIB_ITEM("PortAdd", MPTCP_MIB_PORTADD),
SNMP_MIB_ITEM("AddAddrDrop", MPTCP_MIB_ADDADDRDROP),
SNMP_MIB_ITEM("MPJoinPortSynRx", MPTCP_MIB_JOINPORTSYNRX),
SNMP_MIB_ITEM("MPJoinPortSynAckRx", MPTCP_MIB_JOINPORTSYNACKRX),
SNMP_MIB_ITEM("MPJoinPortAckRx", MPTCP_MIB_JOINPORTACKRX),
SNMP_MIB_ITEM("MismatchPortSynRx", MPTCP_MIB_MISMATCHPORTSYNRX),
SNMP_MIB_ITEM("MismatchPortAckRx", MPTCP_MIB_MISMATCHPORTACKRX),
SNMP_MIB_ITEM("RmAddr", MPTCP_MIB_RMADDR),
SNMP_MIB_ITEM("RmAddrDrop", MPTCP_MIB_RMADDRDROP),
SNMP_MIB_ITEM("RmAddrTx", MPTCP_MIB_RMADDRTX),
SNMP_MIB_ITEM("RmAddrTxDrop", MPTCP_MIB_RMADDRTXDROP),
SNMP_MIB_ITEM("RmSubflow", MPTCP_MIB_RMSUBFLOW),
SNMP_MIB_ITEM("MPPrioTx", MPTCP_MIB_MPPRIOTX),
SNMP_MIB_ITEM("MPPrioRx", MPTCP_MIB_MPPRIORX),
SNMP_MIB_ITEM("MPFailTx", MPTCP_MIB_MPFAILTX),
SNMP_MIB_ITEM("MPFailRx", MPTCP_MIB_MPFAILRX),
SNMP_MIB_ITEM("MPFastcloseTx", MPTCP_MIB_MPFASTCLOSETX),
SNMP_MIB_ITEM("MPFastcloseRx", MPTCP_MIB_MPFASTCLOSERX),
SNMP_MIB_ITEM("MPRstTx", MPTCP_MIB_MPRSTTX),
SNMP_MIB_ITEM("MPRstRx", MPTCP_MIB_MPRSTRX),
SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED),
SNMP_MIB_ITEM("SubflowStale", MPTCP_MIB_SUBFLOWSTALE),
SNMP_MIB_ITEM("SubflowRecover", MPTCP_MIB_SUBFLOWRECOVER),
SNMP_MIB_ITEM("SndWndShared", MPTCP_MIB_SNDWNDSHARED),
SNMP_MIB_ITEM("RcvWndShared", MPTCP_MIB_RCVWNDSHARED),
SNMP_MIB_ITEM("RcvWndConflictUpdate", MPTCP_MIB_RCVWNDCONFLICTUPDATE),
SNMP_MIB_ITEM("RcvWndConflict", MPTCP_MIB_RCVWNDCONFLICT),
SNMP_MIB_SENTINEL
};
/* mptcp_mib_alloc - allocate percpu mib counters
*
* These are allocated when the first mptcp socket is created so
* we do not waste percpu memory if mptcp isn't in use.
*/
bool mptcp_mib_alloc(struct net *net)
{
struct mptcp_mib __percpu *mib = alloc_percpu(struct mptcp_mib);
if (!mib)
return false;
if (cmpxchg(&net->mib.mptcp_statistics, NULL, mib))
free_percpu(mib);
return true;
}
void mptcp_seq_show(struct seq_file *seq)
{
unsigned long sum[ARRAY_SIZE(mptcp_snmp_list) - 1];
struct net *net = seq->private;
int i;
seq_puts(seq, "MPTcpExt:");
for (i = 0; mptcp_snmp_list[i].name; i++)
seq_printf(seq, " %s", mptcp_snmp_list[i].name);
seq_puts(seq, "\nMPTcpExt:");
memset(sum, 0, sizeof(sum));
if (net->mib.mptcp_statistics)
snmp_get_cpu_field_batch(sum, mptcp_snmp_list,
net->mib.mptcp_statistics);
for (i = 0; mptcp_snmp_list[i].name; i++)
seq_printf(seq, " %lu", sum[i]);
seq_putc(seq, '\n');
}
3.代码分析
文件路径：include/net/snmp.h
//这个宏只是定义了一个指针类型的变量
//如：struct mptcp_mib __percpu *mptcp_statistics
/*
struct mptcp_mib {
unsigned long mibs[LINUX_MIB_MPTCP_MAX];
};
*/
#define DEFINE_SNMP_STAT(type, name) \
__typeof__(type) __percpu *name
文件路径：include/net/netns/mib.h
//可以看到这个结构存放了很多协议的mib信息
struct netns_mib {
DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics);
#if IS_ENABLED(CONFIG_IPV6)
DEFINE_SNMP_STAT(struct ipstats_mib, ipv6_statistics);
#endif
DEFINE_SNMP_STAT(struct tcp_mib, tcp_statistics);
DEFINE_SNMP_STAT(struct linux_mib, net_statistics);
DEFINE_SNMP_STAT(struct udp_mib, udp_statistics);
#if IS_ENABLED(CONFIG_IPV6)
DEFINE_SNMP_STAT(struct udp_mib, udp_stats_in6);
#endif
#ifdef CONFIG_XFRM_STATISTICS
DEFINE_SNMP_STAT(struct linux_xfrm_mib, xfrm_statistics);
#endif
#if IS_ENABLED(CONFIG_TLS)
DEFINE_SNMP_STAT(struct linux_tls_mib, tls_statistics);
#endif
#ifdef CONFIG_MPTCP
DEFINE_SNMP_STAT(struct mptcp_mib, mptcp_statistics); //这是我们关注的mptcp相关的
#endif
DEFINE_SNMP_STAT(struct udp_mib, udplite_statistics);
#if IS_ENABLED(CONFIG_IPV6)
DEFINE_SNMP_STAT(struct udp_mib, udplite_stats_in6);
#endif
DEFINE_SNMP_STAT(struct icmp_mib, icmp_statistics);
DEFINE_SNMP_STAT_ATOMIC(struct icmpmsg_mib, icmpmsg_statistics);
#if IS_ENABLED(CONFIG_IPV6)
DEFINE_SNMP_STAT(struct icmpv6_mib, icmpv6_statistics);
DEFINE_SNMP_STAT_ATOMIC(struct icmpv6msg_mib, icmpv6msg_statistics);
struct proc_dir_entry *proc_net_devsnmp6;
#endif
};
文件路径：include/net/net_namespace.h
struct net {
...
struct netns_mib mib; //每个网络命名空间都有一个
...
struct netns_ipv4 ipv4;
...
}
文件路径：net/mptcp/mib.h
/* SPDX-License-Identifier: GPL-2.0-or-later */
enum linux_mptcp_mib_field {
MPTCP_MIB_NUM = 0,
MPTCP_MIB_MPCAPABLEPASSIVE, /* Received SYN with MP_CAPABLE */
MPTCP_MIB_MPCAPABLEACTIVE, /* Sent SYN with MP_CAPABLE */
MPTCP_MIB_MPCAPABLEACTIVEACK, /* Received SYN/ACK with MP_CAPABLE */
MPTCP_MIB_MPCAPABLEPASSIVEACK, /* Received third ACK with MP_CAPABLE */
MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK,/* Server-side fallback during 3-way handshake */
MPTCP_MIB_MPCAPABLEACTIVEFALLBACK, /* Client-side fallback during 3-way handshake */
MPTCP_MIB_TOKENFALLBACKINIT, /* Could not init/allocate token */
MPTCP_MIB_RETRANSSEGS, /* Segments retransmitted at the MPTCP-level */
MPTCP_MIB_JOINNOTOKEN, /* Received MP_JOIN but the token was not found */
MPTCP_MIB_JOINSYNRX, /* Received a SYN + MP_JOIN */
MPTCP_MIB_JOINSYNACKRX, /* Received a SYN/ACK + MP_JOIN */
MPTCP_MIB_JOINSYNACKMAC, /* HMAC was wrong on SYN/ACK + MP_JOIN */
MPTCP_MIB_JOINACKRX, /* Received an ACK + MP_JOIN */
MPTCP_MIB_JOINACKMAC, /* HMAC was wrong on ACK + MP_JOIN */
MPTCP_MIB_DSSNOMATCH, /* Received a new mapping that did not match the previous one */
MPTCP_MIB_INFINITEMAPTX, /* Sent an infinite mapping */
MPTCP_MIB_INFINITEMAPRX, /* Received an infinite mapping */
MPTCP_MIB_DSSTCPMISMATCH, /* DSS-mapping did not map with TCP's sequence numbers */
MPTCP_MIB_DATACSUMERR, /* The data checksum fail */
MPTCP_MIB_OFOQUEUETAIL, /* Segments inserted into OoO queue tail */
MPTCP_MIB_OFOQUEUE, /* Segments inserted into OoO queue */
MPTCP_MIB_OFOMERGE, /* Segments merged in OoO queue */
MPTCP_MIB_NODSSWINDOW, /* Segments not in MPTCP windows */
MPTCP_MIB_DUPDATA, /* Segments discarded due to duplicate DSS */
MPTCP_MIB_ADDADDR, /* Received ADD_ADDR with echo-flag=0 */
MPTCP_MIB_ADDADDRTX, /* Sent ADD_ADDR with echo-flag=0 */
MPTCP_MIB_ADDADDRTXDROP, /* ADD_ADDR with echo-flag=0 not send due to
* resource exhaustion
*/
MPTCP_MIB_ECHOADD, /* Received ADD_ADDR with echo-flag=1 */
MPTCP_MIB_ECHOADDTX, /* Send ADD_ADDR with echo-flag=1 */
MPTCP_MIB_ECHOADDTXDROP, /* ADD_ADDR with echo-flag=1 not send due
* to resource exhaustion
*/
MPTCP_MIB_PORTADD, /* Received ADD_ADDR with a port-number */
MPTCP_MIB_ADDADDRDROP, /* Dropped incoming ADD_ADDR */
MPTCP_MIB_JOINPORTSYNRX, /* Received a SYN MP_JOIN with a different port-number */
MPTCP_MIB_JOINPORTSYNACKRX, /* Received a SYNACK MP_JOIN with a different port-number */
MPTCP_MIB_JOINPORTACKRX, /* Received an ACK MP_JOIN with a different port-number */
MPTCP_MIB_MISMATCHPORTSYNRX, /* Received a SYN MP_JOIN with a mismatched port-number */
MPTCP_MIB_MISMATCHPORTACKRX, /* Received an ACK MP_JOIN with a mismatched port-number */
MPTCP_MIB_RMADDR, /* Received RM_ADDR */
MPTCP_MIB_RMADDRDROP, /* Dropped incoming RM_ADDR */
MPTCP_MIB_RMADDRTX, /* Sent RM_ADDR */
MPTCP_MIB_RMADDRTXDROP, /* RM_ADDR not sent due to resource exhaustion */
MPTCP_MIB_RMSUBFLOW, /* Remove a subflow */
MPTCP_MIB_MPPRIOTX, /* Transmit a MP_PRIO */
MPTCP_MIB_MPPRIORX, /* Received a MP_PRIO */
MPTCP_MIB_MPFAILTX, /* Transmit a MP_FAIL */
MPTCP_MIB_MPFAILRX, /* Received a MP_FAIL */
MPTCP_MIB_MPFASTCLOSETX, /* Transmit a MP_FASTCLOSE */
MPTCP_MIB_MPFASTCLOSERX, /* Received a MP_FASTCLOSE */
MPTCP_MIB_MPRSTTX, /* Transmit a MP_RST */
MPTCP_MIB_MPRSTRX, /* Received a MP_RST */
MPTCP_MIB_RCVPRUNED, /* Incoming packet dropped due to memory limit */
MPTCP_MIB_SUBFLOWSTALE, /* Subflows entered 'stale' status */
MPTCP_MIB_SUBFLOWRECOVER, /* Subflows returned to active status after being stale */
MPTCP_MIB_SNDWNDSHARED, /* Subflow snd wnd is overridden by msk's one */
MPTCP_MIB_RCVWNDSHARED, /* Subflow rcv wnd is overridden by msk's one */
MPTCP_MIB_RCVWNDCONFLICTUPDATE, /* subflow rcv wnd is overridden by msk's one due to
* conflict with another subflow while updating msk rcv wnd
*/
MPTCP_MIB_RCVWNDCONFLICT, /* Conflict with while updating msk rcv wnd */
__MPTCP_MIB_MAX
};
#define LINUX_MIB_MPTCP_MAX __MPTCP_MIB_MAX
//可以看到mptcp_mib里面就是一个数组，用来存放mptcp协议相关的mib信息
struct mptcp_mib {
unsigned long mibs[LINUX_MIB_MPTCP_MAX];
};
static inline void MPTCP_ADD_STATS(struct net *net,
enum linux_mptcp_mib_field field,
int val)
{
if (likely(net->mib.mptcp_statistics))
SNMP_ADD_STATS(net->mib.mptcp_statistics, field, val);
}
static inline void MPTCP_INC_STATS(struct net *net,
enum linux_mptcp_mib_field field)
{
if (likely(net->mib.mptcp_statistics))
SNMP_INC_STATS(net->mib.mptcp_statistics, field);
}
static inline void __MPTCP_INC_STATS(struct net *net,
enum linux_mptcp_mib_field field)
{
if (likely(net->mib.mptcp_statistics))
__SNMP_INC_STATS(net->mib.mptcp_statistics, field);
}
文件路径：include/net/snmp.h
struct snmp_mib {
const char *name;
int entry;
};
//填充struct snmp_mib结构
#define SNMP_MIB_ITEM(_name,_entry) { \
.name = _name, \
.entry = _entry, \
}
文件路径：net/mptcp/mib.c
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/seq_file.h>
#include <net/ip.h>
#include <net/mptcp.h>
#include <net/snmp.h>
#include <net/net_namespace.h>
#include "mib.h"
static const struct snmp_mib mptcp_snmp_list[] = {
SNMP_MIB_ITEM("MPCapableSYNRX", MPTCP_MIB_MPCAPABLEPASSIVE),
SNMP_MIB_ITEM("MPCapableSYNTX", MPTCP_MIB_MPCAPABLEACTIVE),
SNMP_MIB_ITEM("MPCapableSYNACKRX", MPTCP_MIB_MPCAPABLEACTIVEACK),
SNMP_MIB_ITEM("MPCapableACKRX", MPTCP_MIB_MPCAPABLEPASSIVEACK),
SNMP_MIB_ITEM("MPCapableFallbackACK", MPTCP_MIB_MPCAPABLEPASSIVEFALLBACK),
SNMP_MIB_ITEM("MPCapableFallbackSYNACK", MPTCP_MIB_MPCAPABLEACTIVEFALLBACK),
SNMP_MIB_ITEM("MPFallbackTokenInit", MPTCP_MIB_TOKENFALLBACKINIT),
SNMP_MIB_ITEM("MPTCPRetrans", MPTCP_MIB_RETRANSSEGS),
SNMP_MIB_ITEM("MPJoinNoTokenFound", MPTCP_MIB_JOINNOTOKEN),
SNMP_MIB_ITEM("MPJoinSynRx", MPTCP_MIB_JOINSYNRX),
SNMP_MIB_ITEM("MPJoinSynAckRx", MPTCP_MIB_JOINSYNACKRX),
SNMP_MIB_ITEM("MPJoinSynAckHMacFailure", MPTCP_MIB_JOINSYNACKMAC),
SNMP_MIB_ITEM("MPJoinAckRx", MPTCP_MIB_JOINACKRX),
SNMP_MIB_ITEM("MPJoinAckHMacFailure", MPTCP_MIB_JOINACKMAC),
SNMP_MIB_ITEM("DSSNotMatching", MPTCP_MIB_DSSNOMATCH),
SNMP_MIB_ITEM("InfiniteMapTx", MPTCP_MIB_INFINITEMAPTX),
SNMP_MIB_ITEM("InfiniteMapRx", MPTCP_MIB_INFINITEMAPRX),
SNMP_MIB_ITEM("DSSNoMatchTCP", MPTCP_MIB_DSSTCPMISMATCH),
SNMP_MIB_ITEM("DataCsumErr", MPTCP_MIB_DATACSUMERR),
SNMP_MIB_ITEM("OFOQueueTail", MPTCP_MIB_OFOQUEUETAIL),
SNMP_MIB_ITEM("OFOQueue", MPTCP_MIB_OFOQUEUE),
SNMP_MIB_ITEM("OFOMerge", MPTCP_MIB_OFOMERGE),
SNMP_MIB_ITEM("NoDSSInWindow", MPTCP_MIB_NODSSWINDOW),
SNMP_MIB_ITEM("DuplicateData", MPTCP_MIB_DUPDATA),
SNMP_MIB_ITEM("AddAddr", MPTCP_MIB_ADDADDR),
SNMP_MIB_ITEM("AddAddrTx", MPTCP_MIB_ADDADDRTX),
SNMP_MIB_ITEM("AddAddrTxDrop", MPTCP_MIB_ADDADDRTXDROP),
SNMP_MIB_ITEM("EchoAdd", MPTCP_MIB_ECHOADD),
SNMP_MIB_ITEM("EchoAddTx", MPTCP_MIB_ECHOADDTX),
SNMP_MIB_ITEM("EchoAddTxDrop", MPTCP_MIB_ECHOADDTXDROP),
SNMP_MIB_ITEM("PortAdd", MPTCP_MIB_PORTADD),
SNMP_MIB_ITEM("AddAddrDrop", MPTCP_MIB_ADDADDRDROP),
SNMP_MIB_ITEM("MPJoinPortSynRx", MPTCP_MIB_JOINPORTSYNRX),
SNMP_MIB_ITEM("MPJoinPortSynAckRx", MPTCP_MIB_JOINPORTSYNACKRX),
SNMP_MIB_ITEM("MPJoinPortAckRx", MPTCP_MIB_JOINPORTACKRX),
SNMP_MIB_ITEM("MismatchPortSynRx", MPTCP_MIB_MISMATCHPORTSYNRX),
SNMP_MIB_ITEM("MismatchPortAckRx", MPTCP_MIB_MISMATCHPORTACKRX),
SNMP_MIB_ITEM("RmAddr", MPTCP_MIB_RMADDR),
SNMP_MIB_ITEM("RmAddrDrop", MPTCP_MIB_RMADDRDROP),
SNMP_MIB_ITEM("RmAddrTx", MPTCP_MIB_RMADDRTX),
SNMP_MIB_ITEM("RmAddrTxDrop", MPTCP_MIB_RMADDRTXDROP),
SNMP_MIB_ITEM("RmSubflow", MPTCP_MIB_RMSUBFLOW),
SNMP_MIB_ITEM("MPPrioTx", MPTCP_MIB_MPPRIOTX),
SNMP_MIB_ITEM("MPPrioRx", MPTCP_MIB_MPPRIORX),
SNMP_MIB_ITEM("MPFailTx", MPTCP_MIB_MPFAILTX),
SNMP_MIB_ITEM("MPFailRx", MPTCP_MIB_MPFAILRX),
SNMP_MIB_ITEM("MPFastcloseTx", MPTCP_MIB_MPFASTCLOSETX),
SNMP_MIB_ITEM("MPFastcloseRx", MPTCP_MIB_MPFASTCLOSERX),
SNMP_MIB_ITEM("MPRstTx", MPTCP_MIB_MPRSTTX),
SNMP_MIB_ITEM("MPRstRx", MPTCP_MIB_MPRSTRX),
SNMP_MIB_ITEM("RcvPruned", MPTCP_MIB_RCVPRUNED),
SNMP_MIB_ITEM("SubflowStale", MPTCP_MIB_SUBFLOWSTALE),
SNMP_MIB_ITEM("SubflowRecover", MPTCP_MIB_SUBFLOWRECOVER),
SNMP_MIB_ITEM("SndWndShared", MPTCP_MIB_SNDWNDSHARED),
SNMP_MIB_ITEM("RcvWndShared", MPTCP_MIB_RCVWNDSHARED),
SNMP_MIB_ITEM("RcvWndConflictUpdate", MPTCP_MIB_RCVWNDCONFLICTUPDATE),
SNMP_MIB_ITEM("RcvWndConflict", MPTCP_MIB_RCVWNDCONFLICT),
SNMP_MIB_SENTINEL
};
/* mptcp_mib_alloc - allocate percpu mib counters
*
* These are allocated when the first mptcp socket is created so
* we do not waste percpu memory if mptcp isn't in use.
*/
bool mptcp_mib_alloc(struct net *net)
{
//为每个cpu申请一份struct mptcp_mib内存
struct mptcp_mib __percpu *mib = alloc_percpu(struct mptcp_mib);
if (!mib)
return false;
//struct mptcp_mib __percpu *mptcp_statistics
/*
struct mptcp_mib {
unsigned long mibs[LINUX_MIB_MPTCP_MAX];
};
*/
//将申请的内存传给网络命名空间中net->mib.mptcp_statistics
if (cmpxchg(&net->mib.mptcp_statistics, NULL, mib))
free_percpu(mib);
return true;
}
void mptcp_seq_show(struct seq_file *seq)
{
//这里减一，我觉得是数组最后一个成员SNMP_MIB_SENTINEL是NULL所以要减一
unsigned long sum[ARRAY_SIZE(mptcp_snmp_list) - 1];
//通过struct seq_file这个机构指针获取网络命名空间对象
//这里应该在某个初始化的位置将seq->private指向了net,所以这可以通过eq->private获取net
struct net *net = seq->private;
int i;
//struct seq_file这个结构体是这样的
/*
struct seq_file {
char *buf;
size_t size;
size_t from;
size_t count;
size_t pad_until;
loff_t index;
loff_t read_pos;
struct mutex lock;
const struct seq_operations *op;
int poll_event;
const struct file *file;
void *private;
};
*/
//将字符"MPTcpExt:"存入seq->buf中
seq_puts(seq, "MPTcpExt:");
for (i = 0; mptcp_snmp_list[i].name; i++)
//遍历mptcp_snmp_list数组将.name的信息名称依次存入seq->buf中
seq_printf(seq, " %s", mptcp_snmp_list[i].name);
//将字符"\nMPTcpExt:"存入seq->buf中，在前面加一个换行是为了另起一行
/*如
MPTcpExt: name1 name2 name3
MPTcpExt:
*/
seq_puts(seq, "\nMPTcpExt:");
//sum数组清零
memset(sum, 0, sizeof(sum));
if (net->mib.mptcp_statistics)
//将net->mib.mptcp_statistics中的mptcp的mib信息传给sum数组
snmp_get_cpu_field_batch(sum, mptcp_snmp_list,
net->mib.mptcp_statistics);
for (i = 0; mptcp_snmp_list[i].name; i++)
//将获取到mptcp的mib信息也填入seq->buf中
seq_printf(seq, " %lu", sum[i]);
/*最终形成
MPTcpExt: name1 name2 name3
MPTcpExt: data1 data2 data3
*/
//最后加换行，和下一个协议隔开
seq_putc(seq, '\n');
}
4.总结
这个文件的主要作用是
1.为每个cpu申请一份struct mptcp_mib内存
2.将mptcp的mib信息从net命名空间获取，然后给到seq_file结构中
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