對(duì)于各個(gè)協(xié)議生成的路由信息的處理屬于quagga中非常重要的一個(gè)功能，如何在內(nèi)核進(jìn)行路由增加，更新，刪除是一個(gè)復(fù)雜的過(guò)程。

quagga在thread任務(wù)調(diào)度中加入了一種工作隊(duì)列，work_queue，與內(nèi)核的工作隊(duì)列類(lèi)似，是一種相對(duì)而言，低優(yōu)先級(jí)的任務(wù)，這里的任務(wù)看成類(lèi)似的系統(tǒng)進(jìn)程。

1、隊(duì)列初始化：

1 /* initialise zebra rib work queue */ 2 static void 3 rib_queue_init(struct zebra_t *zebra) 4 { 5 assert(zebra); 6 7 if (!(zebra->ribq = work_queue_new(zebra->master, 8 "route_node processing"))) 9 { 10 zlog_err("%s: could not initialise work queue!", __func__); 11 return; 12 } 13 14 /* fill in the work queue spec */ 15 zebra->ribq->spec.workfunc = &meta_queue_process; 16 zebra->ribq->spec.errorfunc = NULL; 17 /* XXX: TODO: These should be runtime configurable via vty */ 18 zebra->ribq->spec.max_retries = 3; 19 zebra->ribq->spec.hold = rib_process_hold_time; 20 21 if (!(zebra->mq = meta_queue_new())) 22 { 23 zlog_err("%s: could not initialise meta queue!", __func__); 24 return; 25 } 26 return; 27 }

第19行，zebra->ribq->spec.hold = rib_process_hold_time; 指定了rib工作隊(duì)列在thread_fetch的時(shí)候會(huì)等待10毫秒

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1 /* Hold time for RIB process, should be very minimal. 2 * it is useful to able to set it otherwise for testing, hence exported 3 * as global here for test-rig code. 4 */ 5 int rib_process_hold_time = 10;

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在添加thread任務(wù)的時(shí)候進(jìn)行了時(shí)間單位換算：

1 /* Add a background thread, with an optional millisec delay */ 2 struct thread* 3 funcname_thread_add_background(struct thread_master *m, 4 int (*func)(struct thread *), 5 void *arg, long delay, 6 debugargdef) { 7 struct timeval trel; 8 9 assert(m != NULL); 10 11 if (delay) { 12 trel.tv_sec = delay / 1000; 13 trel.tv_usec = 1000 * (delay % 1000); 14 } else { 15 trel.tv_sec = 0; 16 trel.tv_usec = 0; 17 } 18 19 return funcname_thread_add_timer_timeval(m, func, THREAD_BACKGROUND, 20 arg, &trel, debugargpass); 21 }

OK，meta_queue_process，就指定了工作隊(duì)列在調(diào)度執(zhí)行的處理函數(shù)，由此guagga就會(huì)一直同步更新路由了。

2、每個(gè)子網(wǎng)的下一跳路由表項(xiàng)的描述：

quagga使用了雙向鏈表來(lái)管理表項(xiàng)，定義了路由表現(xiàn)的詳細(xì)信息，但比如 status 這個(gè)字段是用來(lái)在更新路由時(shí)來(lái)做比較的關(guān)鍵字段。如下宏定義了3種狀態(tài)：

#define RIB_ENTRY_REMOVED?? ?(1 << 0)
#define RIB_ENTRY_CHANGED?? ?(1 << 1)
#define RIB_ENTRY_SELECTED_FIB?? ?(1 << 2)

1 struct rib { 2 struct rib *next; /* Link list. */ 3 struct rib *prev; 4 struct nexthop *nexthop; /* Nexthop structure */ 5 unsigned long refcnt; /* Refrence count. */ 6 time_t uptime; /* Uptime. */ 7 int type; /* Type fo this route. */ 8 vrf_id_t vrf_id; /* VRF identifier. */ 9 int table; /* Which routing table */ 10 u_int32_t metric; /* Metric */ 11 u_int32_t mtu; /* MTU */ 12 u_int32_t nexthop_mtu; 13 u_char distance; /* Distance. */ 14 u_char flags; /* Flags of this route. in lib/zebra.h ZEBRA_FLAG_* */ 15 u_char status; /* RIB internal status */ 16 #define RIB_ENTRY_REMOVED (1 << 0) 17 #define RIB_ENTRY_CHANGED (1 << 1) 18 #define RIB_ENTRY_SELECTED_FIB (1 << 2) 19 u_char nexthop_num; /* Nexthop information. */ 20 u_char nexthop_active_num; 21 u_char nexthop_fib_num; 22 };

?3、整個(gè)路由表的描述：

/* Routing table top structure. */ struct route_table {struct route_node *top;/** Delegate that performs certain functions for this table.*/route_table_delegate_t *delegate;unsigned long count;void *info; /* User data. */ };

route_table包含了一個(gè)二叉樹(shù)結(jié)構(gòu)來(lái)保存所有的路由前綴和下一跳路由表項(xiàng)，prefix結(jié)構(gòu)保持了路由前綴的長(zhǎng)度和值，用來(lái)做最長(zhǎng)前綴匹配：

1 /* Each routing entry. */ 2 struct route_node { 3 struct prefix p; /* Actual prefix of this radix. */ 4 struct route_table *table; /* Tree link. */ 5 struct route_node *parent; 6 struct route_node *link[2]; 7 unsigned int lock; /* Lock of this radix */ 8 void *info; /* Each node of route. */ 9 void *aggregate; /* Aggregation. */ 10 11 #define l_left link[0] 12 #define l_right link[1] 13 };

呃，說(shuō)好的mtire樹(shù)呢? 好吧，我們不太可能把成千上萬(wàn)的路由表項(xiàng)塞給linux內(nèi)核，夠用就行。

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轉(zhuǎn)載于:https://www.cnblogs.com/danxi/p/6285545.html

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