netif_receive_skb->__netif_receive_skb_core

 ?1 /* 将skb传递到上层 */ ?2 static int __netif_receive_skb_core(struct sk_buff *skb, bool pfmemalloc) ?3 { ?4 ????struct packet_type *ptype, *pt_prev; ?5 ????rx_handler_func_t *rx_handler; ?6 ????struct net_device *orig_dev; ?7 ????bool deliver_exact = false; ?8 ????int ret = NET_RX_DROP; ?9 ????__be16 type; 10 ?11 ????/* 记录收包时间，netdev_tstamp_prequeue为0，表示可能有包延迟 */ 12 ????net_timestamp_check(!netdev_tstamp_prequeue, skb); 13 ?14 ????trace_netif_receive_skb(skb); 15 ?16 ????/* 记录收包设备 */ 17 ????orig_dev = skb->dev; 18 ?19 ????/* 重置各层头部 */ 20 ????skb_reset_network_header(skb); 21 ????if (!skb_transport_header_was_set(skb)) 22 ????????skb_reset_transport_header(skb); 23 ????skb_reset_mac_len(skb); 24 ?25 ????/* ?26 ????????留下一个节点，最后一次向上层传递时， 27 ????????不需要在inc引用，回调中会free 28 ????????这样相当于少调用了一次free 29 ????*/ 30 ????pt_prev = NULL; 31 ?32 another_round: 33 ?34 ????/* 接收设备索引号 */ 35 ????skb->skb_iif = skb->dev->ifindex; 36 ?37 ????/* 处理包数统计 */ 38 ????__this_cpu_inc(softnet_data.processed); 39 ?40 ????/* vlan包，则去掉vlan头 */ 41 ????if (skb->protocol == cpu_to_be16(ETH_P_8021Q) || 42 ????????skb->protocol == cpu_to_be16(ETH_P_8021AD)) { 43 ?44 ????????/* 45 ????????????这里改了三层协议，protocol指向ip等 46 ????????????another_round不会再走这里 47 ????????*/ 48 ????????skb = skb_vlan_untag(skb); 49 ????????if (unlikely(!skb)) 50 ????????????goto out; 51 ????} 52 ?53 ????/* 不对数据包进行分类 */ 54 ????if (skb_skip_tc_classify(skb)) 55 ????????goto skip_classify; 56 ?57 ????/* prmemalloc */ 58 ????if (pfmemalloc) 59 ????????goto skip_taps; 60 ?61 ?62 ????/* 下面两个是未(指定)设备的所有协议传递的上层传递 */ 63 ?64 ?65 ????/* 如抓包程序未指定设备 */ ????66 ????/* 进行未指定设备的全局链表对应协议的skb上层传递 */ 67 ????list_for_each_entry_rcu(ptype, &ptype_all, list) { 68 ????????if (pt_prev) 69 ????????????ret = deliver_skb(skb, pt_prev, orig_dev); 70 ????????pt_prev = ptype; 71 ????} 72 ?73 ????/* 如抓包程序指定了设备 */ 74 ????/* 进行指定设备的协议链表的skb上层传递 */ 75 ????list_for_each_entry_rcu(ptype, &skb->dev->ptype_all, list) { 76 ????????if (pt_prev) 77 ????????????ret = deliver_skb(skb, pt_prev, orig_dev); 78 ????????pt_prev = ptype; 79 ????} 80 ?81 skip_taps: 82 #ifdef CONFIG_NET_INGRESS 83 ????if (static_key_false(&ingress_needed)) { 84 ????????skb = sch_handle_ingress(skb, &pt_prev, &ret, orig_dev); 85 ????????if (!skb) 86 ????????????goto out; 87 ?88 ????????if (nf_ingress(skb, &pt_prev, &ret, orig_dev) < 0) 89 ????????????goto out; 90 ????} 91 #endif 92 ????skb_reset_tc(skb); 93 skip_classify: 94 ?95 ????/* 不支持使用pfmemalloc */ 96 ????if (pfmemalloc && !skb_pfmemalloc_protocol(skb)) 97 ????????goto drop; 98 ?99 ????/* 如果是vlan包 */100 ????if (skb_vlan_tag_present(skb)) {101 ????????/* 处理prev */102 ????????if (pt_prev) {103 ????????????ret = deliver_skb(skb, pt_prev, orig_dev);104 ????????????pt_prev = NULL;105 ????????}106 107 ????????/* 根据实际的vlan设备调整信息，再走一遍 */108 ????????if (vlan_do_receive(&skb))109 ????????????goto another_round;110 ????????else if (unlikely(!skb))111 ????????????goto out;112 ????}113 114 ????/* 如果有注册handler，那么调用，比如网桥模块 */115 ????rx_handler = rcu_dereference(skb->dev->rx_handler);116 ????if (rx_handler) {117 ????????if (pt_prev) {118 ????????????ret = deliver_skb(skb, pt_prev, orig_dev);119 ????????????pt_prev = NULL;120 ????????}121 ????????switch (rx_handler(&skb)) {122 ????????????/* 已处理，无需进一步处理 */123 ????????case RX_HANDLER_CONSUMED:124 ????????????ret = NET_RX_SUCCESS;125 ????????????goto out;126 ????????????/* 修改了skb->dev，在处理一次 */127 ????????case RX_HANDLER_ANOTHER:128 ????????????goto another_round;129 ????????????/* 精确传递到ptype->dev == skb->dev */130 ????????case RX_HANDLER_EXACT:131 ????????????deliver_exact = true;132 ????????????/* 正常传递即可 */133 ????????case RX_HANDLER_PASS:134 ????????????break;135 ????????default:136 ????????????BUG();137 ????????}138 ????}139 140 ????/* 还有vlan标记，说明找不到vlanid对应的设备 */141 ????if (unlikely(skb_vlan_tag_present(skb))) {142 ????????/* 存在vlanid，则判定是到其他设备的包 */143 ????????if (skb_vlan_tag_get_id(skb))144 ????????????skb->pkt_type = PACKET_OTHERHOST;145 ????????/* Note: we might in the future use prio bits146 ?????????* and set skb->priority like in vlan_do_receive()147 ?????????* For the time being, just ignore Priority Code Point148 ?????????*/149 ????????skb->vlan_tci = 0;150 ????}151 152 ????/* 设置三层协议，下面提交都是按照三层协议提交的 */153 ????type = skb->protocol;154 155 ????/* deliver only exact match when indicated */156 ????/* 未设置精确发送，则向未指定设备的指定协议全局发送一份 */157 ????if (likely(!deliver_exact)) {158 ????????deliver_ptype_list_skb(skb, &pt_prev, orig_dev, type,159 ???????????????????????&ptype_base[ntohs(type) &160 ???????????????????????????PTYPE_HASH_MASK]);161 ????}162 163 ????/* 指定设备的，向原设备上层传递 ?*/164 ????deliver_ptype_list_skb(skb, &pt_prev, orig_dev, type,165 ???????????????????&orig_dev->ptype_specific);166 167 ????/* ?当前设备与原设备不同，向当前设备传递 */168 ????if (unlikely(skb->dev != orig_dev)) {169 ????????deliver_ptype_list_skb(skb, &pt_prev, orig_dev, type,170 ???????????????????????&skb->dev->ptype_specific);171 ????}172 173 ????if (pt_prev) {174 ????????if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))175 ????????????goto drop;176 ????????else177 ????????????/*178 ????????????????使用pt_prev这里就不需要deliver_skb来inc应用数了179 ????????????????func执行内部会free，减少了一次skb_free180 ????????????*/181 ????????????/* 传递到上层*/182 ????????????ret = pt_prev->func(skb, skb->dev, pt_prev, orig_dev);183 ????} else {184 drop:185 ????????if (!deliver_exact)186 ????????????atomic_long_inc(&skb->dev->rx_dropped);187 ????????else188 ????????????atomic_long_inc(&skb->dev->rx_nohandler);189 ????????kfree_skb(skb);190 ????????/* Jamal, now you will not able to escape explaining191 ?????????* me how you were going to use this. :-)192 ?????????*/193 ????????ret = NET_RX_DROP;194 ????}195 196 out:197 ????return ret;198 }