【Linux網路核心】常用函數總結__Oracle

以下函數全部基於3.10.90版本的核心，對於更老或者更新的核心，可能會有所區別。 用於LOG輸出的宏 LOG宏的使用方式與printk完全相同 可以自訂tag，用於在dmesg輸出的日誌中過濾出屬於本模組的資訊 可以通過debug宏控制是否輸出日誌，當關閉日誌後，所有日誌代碼不會被編譯

#define debug 1#define MOD_TAG "custom tag"#if debug#define LOG(fmt, args...) \do{\    printk("[%s]:", MOD_TAG);\    printk(fmt, ##args);\    printk("\n");\}while(0)#else#define LOG(msg)#endif

擷取sk_buff中的saddr和daddr

在擷取IP的時候，一定要確定此時sk_buff中是存在IP的。
因為可能在很多函數中都會調用這個函數，為了區分調用者，增加了caller這個參數，可以傳入一個字串或者直接使用__FUNCTION__。

static void show_skb_ip(struct sk_buff *skb, const char *caller){    LOG("called by %s", caller);    struct iphdr *iph = NULL;    unsigned char *ip = NULL;    iph = ip_hdr(skb);    ip = (unsigned char*)&iph->daddr;    LOG("daddr:%d.%d.%d.%d", ip[0], ip[1], ip[2], ip[3]);    ip = (unsigned char*)&iph->saddr;    LOG("saddr:%d.%d.%d.%d", ip[0], ip[1], ip[2], ip[3]);}

擷取網卡裝置的IP地址

static __be32 get_dev_addr(char *dev_name){    struct net_device *net_dev;    struct in_ifaddr *ifaddr;    if(!dev_name)        goto err_name_null;    net_dev = dev_get_by_name(&init_net, dev_name);    ifaddr = net_dev->ip_ptr->ifa_list;    if(!ifaddr)        goto err_ifaddr_null;    LOG("%s %x", __FUNCTION__, ifaddr->ifa_local);    return ifaddr->ifa_local;err_name_null:    LOG("device name is NULL");    return 0;err_ifaddr_null:    LOG("ifaddr is NULL, maybe it has no ip address");    return 0;}

擷取區域網路其它裝置的MAC地址

利用鄰居子系統的arp_table查詢其它裝置的MAC地址，需要知道對方的IP地址，以及所尋找裝置所對應的網卡介面。

static char *get_neigh_ha(struct net_device *dev, __be32 ip){    struct neighbour *neigh;    if(!dev)        goto err_no_such_dev;    neigh = neigh_lookup(&arp_tbl, &ip, dev);    if(!neigh)        goto err_no_such_neigh;    return neigh->ha;err_no_such_dev:    LOG("%s:no such device", __FUNCTION__);    return NULL;err_no_such_neigh:    LOG("%s:no such neigh", __FUNCTION__);    return NULL;}

擷取網卡當前的IP地址

static __be32 get_dev_addr(char *dev_name){    struct net_device *net_dev;    struct in_ifaddr *ifaddr;    if(!dev_name)        goto err_name_null;    net_dev = dev_get_by_name(&init_net, dev_name);    ifaddr = net_dev->ip_ptr->ifa_list;    if(!ifaddr)        goto err_ifaddr_null;    LOG("%s %x", __FUNCTION__, ifaddr->ifa_local);    return ifaddr->ifa_local;err_name_null:    LOG("device name is NULL");    return 0;err_ifaddr_null:    LOG("ifaddr is NULL, maybe it has no ip address");    return 0;}

強制向區域網路中的某台裝置發送資料包，而忽略目的IP

static int dev_xmit(struct sk_buff *skb, char *dev_name, __be32 target_ip){    int err;    unsigned char *neigh_ha,                  *local_ha;    struct ethhdr *mac_h;    struct net_device *dev;    dev = dev_get_by_name(&init_net, dev_name);    if(!dev)        goto err_get_dev;    neigh_ha = get_neigh_ha(dev, target_ip);    if(!neigh_ha)        goto err_get_neigh;    show_ha("neighbor", neigh_ha);    local_ha = dev->dev_addr;    if(!local_ha)        goto err_get_local;    show_ha("local", dev->dev_addr);    skb->dev = dev;    skb->pkt_type = PACKET_OTHERHOST;    skb->protocol = __constant_htons(ETH_P_IP);    skb->ip_summed = CHECKSUM_UNNECESSARY;    skb->priority = 0;    show_skb_ip(skb, __FUNCTION__);    skb_push(skb, sizeof(struct ethhdr));    skb_reset_mac_header(skb);    mac_h = eth_hdr(skb);    memset(mac_h, 0, sizeof(struct ethhdr));    mac_h->h_proto = __constant_htons(ETH_P_IP);    memcpy(mac_h->h_source, local_ha, ETH_ALEN);    memcpy(mac_h->h_dest, neigh_ha, ETH_ALEN);    err = dev_queue_xmit(skb);    if(err < 0)        goto err_xmit;    return 0;err_get_dev:    LOG("fail to get dev %s", dev_name);    return -1;err_get_neigh:    LOG("fail to get neighbor %x 's mac address over %s", target_ip, dev_name);    return -1;err_get_local:    LOG("fail to get local mac address");    return -1;err_xmit:    LOG("fail to xmit skb");    return -1;}