char c;
struct sockaddr_in addr;
int s;
s = socket(AF_INET, SOCK_DGRAM, 0);
connect(s, (struct sockaddr*)&addr, sizeof(addr));
write(s, &c, 1);
close(s);
tavi@desktop-tavi:~/src/linux$ ip route list table main
default via 172.30.240.1 dev eth0
172.30.240.0/20 dev eth0 proto kernel scope link src 172.30.249.241
tavi@desktop-tavi:~/src/linux$ ip route list table local
broadcast 127.0.0.0 dev lo proto kernel scope link src 127.0.0.1
local 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1
local 127.0.0.1 dev lo proto kernel scope host src 127.0.0.1
broadcast 127.255.255.255 dev lo proto kernel scope link src 127.0.0.1
broadcast 172.30.240.0 dev eth0 proto kernel scope link src 172.30.249.241
local 172.30.249.241 dev eth0 proto kernel scope host src 172.30.249.241
broadcast 172.30.255.255 dev eth0 proto kernel scope link src 172.30.249.241
tavi@desktop-tavi:~/src/linux$ ip rule list
0: from all lookup local
32766: from all lookup main
32767: from all lookup default
struct sk_buff {
struct sk_buff *next;
struct sk_buff *prev;
struct sock *sk;
ktime_t tstamp;
struct net_device *dev;
char cb[48];
unsigned int len,
data_len;
__u16 mac_len,
hdr_len;
void (*destructor)(struct sk_buff *skb);
sk_buff_data_t transport_header;
sk_buff_data_t network_header;
sk_buff_data_t mac_header;
sk_buff_data_t tail;
sk_buff_data_t end;
unsigned char *head,
*data;
unsigned int truesize;
atomic_t users;
/* 预留头部空间 */
void skb_reserve(struct sk_buff *skb, int len);
/* 在尾部添加数据 */
unsigned char *skb_put(struct sk_buff *skb, unsigned int len);
/* 在顶部添加数据 */
unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
/* 丢弃顶部的数据 */
unsigned char *skb_pull(struct sk_buff *skb, unsigned int len);
/* 丢弃尾部的数据 */
unsigned char *skb_trim(struct sk_buff *skb, unsigned int len);
unsigned char *skb_transport_header(const struct sk_buff *skb);
void skb_reset_transport_header(struct sk_buff *skb);
void skb_set_transport_header(struct sk_buff *skb, const int offset);
unsigned char *skb_network_header(const struct sk_buff *skb);
void skb_reset_network_header(struct sk_buff *skb);
void skb_set_network_header(struct sk_buff *skb, const int offset);
unsigned char *skb_mac_header(const struct sk_buff *skb);
int skb_mac_header_was_set(const struct sk_buff *skb);
void skb_reset_mac_header(struct sk_buff *skb);
void skb_set_mac_header(struct sk_buff *skb, const int offset);