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c - SCTP多宿主

转载 作者:IT王子 更新时间:2023-10-28 23:54:25 26 4
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我一直在用 C 开发这个简单的客户端-服务器应用程序,其中客户端只是向服务器发送随机数据,而服务器只是监听客户端发送的内容。我使用的协议(protocol)是 SCTP,我对如何为其实现多宿主功能很感兴趣。

我一直在 Internet 上搜索有关 SCTP 和多宿主的信息,但未能找到任何有关如何指示 SCTP 使用多个地址进行通信的示例。我只找到了在尝试使用多宿主设置 SCTP 时应该使用哪些命令,它应该非常简单。

我创建了一个客户端和一个服务器,它们都使用我的计算机的两个 WLAN 接口(interface)作为它们的连接点。两个适配器都连接到同一个 AP。服务器正在从这些接口(interface)监听来自客户端的数据,客户端通过它们发送数据。问题是,当我断开客户端正在向其发送数据的主要 WLAN 适配器时,传输只是在它应该回退到辅助连接时停止。我用 Wireshark 跟踪了数据包,第一个 INIT 和 INIT_ACK 数据包报告客户端和服务器都在使用 WLAN 适配器作为它们的通信链路。

当我重新连接主要 WLAN 连接时,传输会在一段时间后继续,并向服务器突发大量数据包负载,这是不正确的。数据包应该已经通过辅助连接传输。在许多站点上,据说 SCTP 会自动在连接之间切换,但在我的情况下并没有发生。那么你们是否知道为什么当主链路断开时传输不回退到辅助连接,即使客户端和服务器知道彼此的地址(包括辅助地址)?

关于服务器:

服务器创建一个 SOCK_SEQPACKET 类型套接字并绑定(bind)所有与 INADDR_ANY 找到的接口(interface)。 getladdrs 报告服务器绑定(bind)到 3 个地址(包括 127.0.0.1)。之后,服务器监听套接字并等待客户端发送数据。服务器使用 sctp_recvmsg 调用读取数据。

关于客户:

客户端还创建一个 SEQPACKET 套接字并连接到由命令行参数指定的 IP 地址。在这种情况下,getladdrs 也返回 3 个地址,就像服务器的情况一样。之后客户端才开始向服务器发送数据,延迟一秒到服务器,直到用户使用 Ctrl-C 中断发送。

这是一些源代码:

服务器:

#define BUFFER_SIZE (1 << 16)
#define PORT 10000

int sock, ret, flags;
int i;
int addr_count = 0;
char buffer[BUFFER_SIZE];
socklen_t from_len;

struct sockaddr_in addr;
struct sockaddr_in *laddr[10];
struct sockaddr_in *paddrs[10];
struct sctp_sndrcvinfo sinfo;
struct sctp_event_subscribe event;
struct sctp_prim prim_addr;
struct sctp_paddrparams heartbeat;
struct sigaction sig_handler;

void handle_signal(int signum);

int main(void)
{
if((sock = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP)) < 0)
perror("socket");

memset(&addr, 0, sizeof(struct sockaddr_in));
memset((void*)&event, 1, sizeof(struct sctp_event_subscribe));

addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(PORT);

from_len = (socklen_t)sizeof(struct sockaddr_in);

sig_handler.sa_handler = handle_signal;
sig_handler.sa_flags = 0;

if(sigaction(SIGINT, &sig_handler, NULL) == -1)
perror("sigaction");

if(setsockopt(sock, IPPROTO_SCTP, SCTP_EVENTS, &event, sizeof(struct sctp_event_subscribe)) < 0)
perror("setsockopt");

if(setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(int))< 0)
perror("setsockopt");

if(bind(sock, (struct sockaddr*)&addr, sizeof(struct sockaddr)) < 0)
perror("bind");

if(listen(sock, 2) < 0)
perror("listen");

addr_count = sctp_getladdrs(sock, 0, (struct sockaddr**)laddr);
printf("Addresses binded: %d\n", addr_count);

for(i = 0; i < addr_count; i++)
printf("Address %d: %s:%d\n", i +1, inet_ntoa((*laddr)[i].sin_addr), (*laddr)[i].sin_port);

sctp_freeladdrs((struct sockaddr*)*laddr);

while(1)
{
flags = 0;

ret = sctp_recvmsg(sock, buffer, BUFFER_SIZE, (struct sockaddr*)&addr, &from_len, NULL, &flags);

if(flags & MSG_NOTIFICATION)
printf("Notification received from %s:%u\n", inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));

printf("%d bytes received from %s:%u\n", ret, inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
}

if(close(sock) < 0)
perror("close");
}

void handle_signal(int signum)
{
switch(signum)
{
case SIGINT:
if(close(sock) != 0)
perror("close");
exit(0);
break;
default: exit(0);
break;
}
}

和客户:

#define PORT 10000
#define MSG_SIZE 1000
#define NUMBER_OF_MESSAGES 1000
#define PPID 1234

int sock;
struct sockaddr_in *paddrs[10];
struct sockaddr_in *laddrs[10];

void handle_signal(int signum);

int main(int argc, char **argv)
{
int i;
int counter = 1;
int ret;
int addr_count;
char address[16];
char buffer[MSG_SIZE];
sctp_assoc_t id;
struct sockaddr_in addr;
struct sctp_status status;
struct sctp_initmsg initmsg;
struct sctp_event_subscribe events;
struct sigaction sig_handler;

memset((void*)&buffer, 'j', MSG_SIZE);
memset((void*)&initmsg, 0, sizeof(initmsg));
memset((void*)&addr, 0, sizeof(struct sockaddr_in));
memset((void*)&events, 1, sizeof(struct sctp_event_subscribe));

if(argc != 2 || (inet_addr(argv[1]) == -1))
{
puts("Usage: client [IP ADDRESS in form xxx.xxx.xxx.xxx] ");
return 0;
}

strncpy(address, argv[1], 15);
address[15] = 0;

addr.sin_family = AF_INET;
inet_aton(address, &(addr.sin_addr));
addr.sin_port = htons(PORT);

initmsg.sinit_num_ostreams = 2;
initmsg.sinit_max_instreams = 2;
initmsg.sinit_max_attempts = 5;

sig_handler.sa_handler = handle_signal;
sig_handler.sa_flags = 0;

if(sigaction(SIGINT, &sig_handler, NULL) == -1)
perror("sigaction");

if((sock = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP)) < 0)
perror("socket");

if((setsockopt(sock, SOL_SCTP, SCTP_INITMSG, &initmsg, sizeof(initmsg))) != 0)
perror("setsockopt");

if((setsockopt(sock, SOL_SCTP, SCTP_EVENTS, (const void *)&events, sizeof(events))) != 0)
perror("setsockopt");

if(sendto(sock, buffer, MSG_SIZE, 0, (struct sockaddr*)&addr, sizeof(struct sockaddr)) == -1)
perror("sendto");

addr_count = sctp_getpaddrs(sock, 0, (struct sockaddr**)paddrs);
printf("\nPeer addresses: %d\n", addr_count);

for(i = 0; i < addr_count; i++)
printf("Address %d: %s:%d\n", i +1, inet_ntoa((*paddrs)[i].sin_addr), (*paddrs)[i].sin_port);

sctp_freepaddrs((struct sockaddr*)*paddrs);

addr_count = sctp_getladdrs(sock, 0, (struct sockaddr**)laddrs);
printf("\nLocal addresses: %d\n", addr_count);

for(i = 0; i < addr_count; i++)
printf("Address %d: %s:%d\n", i +1, inet_ntoa((*laddrs)[i].sin_addr), (*laddrs)[i].sin_port);

sctp_freeladdrs((struct sockaddr*)*laddrs);

i = sizeof(status);
if((ret = getsockopt(sock, SOL_SCTP, SCTP_STATUS, &status, (socklen_t *)&i)) != 0)
perror("getsockopt");

printf("\nSCTP Status:\n--------\n");
printf("assoc id = %d\n", status.sstat_assoc_id);
printf("state = %d\n", status.sstat_state);
printf("instrms = %d\n", status.sstat_instrms);
printf("outstrms = %d\n--------\n\n", status.sstat_outstrms);

for(i = 0; i < NUMBER_OF_MESSAGES; i++)
{
counter++;
printf("Sending data chunk #%d...", counter);
if((ret = sendto(sock, buffer, MSG_SIZE, 0, (struct sockaddr*)&addr, sizeof(struct sockaddr))) == -1)
perror("sendto");

printf("Sent %d bytes to peer\n",ret);

sleep(1);
}

if(close(sock) != 0)
perror("close");
}


void handle_signal(int signum)
{

switch(signum)
{
case SIGINT:
if(close(sock) != 0)
perror("close");
exit(0);
break;
default: exit(0);
break;
}

}

那么你们知道我做错了什么吗?

最佳答案

好的,我终于解决了多宿主问题。这就是我所做的。

我使用 sctp_paddrparams 结构将心跳值调整为 5000 毫秒。位于结构中的标志变量必须处于 SPP_HB_ENABLE 模式,否则 SCTP 在尝试使用 setsockopt() 设置值时会忽略心跳值。

这就是为什么 SCTP 没有像我想要的那样频繁地发送心跳的原因。我没有注意到标志变量的原因是我正在阅读的过时的 SCTP 引用指南,其中指出结构中不存在标志变量!较新的引用资料显示有。这样心跳问题就解决了!

另一件事是将 rto_max 值修改为例如 2000 毫秒左右。降低该值会告诉 SCTP 更快地更改路径。默认值为 60 000 毫秒,太高了(开始更改路径前 1 分钟)。可以使用 sctp_rtoinfo 结构调整 rto_max 值。

通过这两项修改,多宿主开始工作。哦,还有一件事。当服务器处于 SEQPACKET 模式时,客户端必须处于 STREAM 模式。客户端使用正常的 send() 命令向服务器发送数据,服务器使用 sctp_recvmsg() 读取数据,其中 addr 结构设置为 NULL。

我希望这些信息能帮助其他为 SCTP 的多宿主而苦苦挣扎的人。为您的意见干杯,这些对我有很大帮助!这是一些代码示例,所以如果您问我,这可能是网络中的第一个多宿主简单示例(除了多流示例之外没有找到任何示例)

服务器:

#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <stdlib.h>
#include <pthread.h>

#define BUFFER_SIZE (1 << 16)
#define PORT 10000

int sock, ret, flags;
int i, reuse = 1;
int addr_count = 0;
char buffer[BUFFER_SIZE];
socklen_t from_len;

struct sockaddr_in addr;
struct sockaddr_in *laddr[10];
struct sockaddr_in *paddrs[10];
struct sctp_sndrcvinfo sinfo;
struct sctp_event_subscribe event;
struct sctp_prim prim_addr;
struct sctp_paddrparams heartbeat;
struct sigaction sig_handler;
struct sctp_rtoinfo rtoinfo;

void handle_signal(int signum);

int main(void)
{
if((sock = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP)) < 0)
perror("socket");

memset(&addr, 0, sizeof(struct sockaddr_in));
memset(&event, 1, sizeof(struct sctp_event_subscribe));
memset(&heartbeat, 0, sizeof(struct sctp_paddrparams));
memset(&rtoinfo, 0, sizeof(struct sctp_rtoinfo));

addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(PORT);

from_len = (socklen_t)sizeof(struct sockaddr_in);

sig_handler.sa_handler = handle_signal;
sig_handler.sa_flags = 0;

heartbeat.spp_flags = SPP_HB_ENABLE;
heartbeat.spp_hbinterval = 5000;
heartbeat.spp_pathmaxrxt = 1;

rtoinfo.srto_max = 2000;

/*Set Heartbeats*/
if(setsockopt(sock, SOL_SCTP, SCTP_PEER_ADDR_PARAMS , &heartbeat, sizeof(heartbeat)) != 0)
perror("setsockopt");

/*Set rto_max*/
if(setsockopt(sock, SOL_SCTP, SCTP_RTOINFO , &rtoinfo, sizeof(rtoinfo)) != 0)
perror("setsockopt");

/*Set Signal Handler*/
if(sigaction(SIGINT, &sig_handler, NULL) == -1)
perror("sigaction");

/*Set Events */
if(setsockopt(sock, IPPROTO_SCTP, SCTP_EVENTS, &event, sizeof(struct sctp_event_subscribe)) < 0)
perror("setsockopt");

/*Set the Reuse of Address*/
if(setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(int))< 0)
perror("setsockopt");

/*Bind the Addresses*/
if(bind(sock, (struct sockaddr*)&addr, sizeof(struct sockaddr)) < 0)
perror("bind");

if(listen(sock, 2) < 0)
perror("listen");

/*Get Heartbeat Value*/
i = (sizeof heartbeat);
getsockopt(sock, SOL_SCTP, SCTP_PEER_ADDR_PARAMS, &heartbeat, (socklen_t*)&i);
printf("Heartbeat interval %d\n", heartbeat.spp_hbinterval);

/*Print Locally Binded Addresses*/
addr_count = sctp_getladdrs(sock, 0, (struct sockaddr**)laddr);
printf("Addresses binded: %d\n", addr_count);
for(i = 0; i < addr_count; i++)
printf("Address %d: %s:%d\n", i +1, inet_ntoa((*laddr)[i].sin_addr), (*laddr)[i].sin_port);
sctp_freeladdrs((struct sockaddr*)*laddr);

while(1)
{
flags = 0;

ret = sctp_recvmsg(sock, buffer, BUFFER_SIZE, NULL, 0, NULL, &flags);

if(flags & MSG_NOTIFICATION)
printf("Notification received from %s:%u\n", inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));

printf("%d bytes received from %s:%u\n", ret, inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
}

if(close(sock) < 0)
perror("close");
}

void handle_signal(int signum)
{
switch(signum)
{
case SIGINT:
if(close(sock) != 0)
perror("close");
exit(0);
break;
default: exit(0);
break;
}
}

客户:

#include <sys/types.h>
#include <sys/socket.h>
#include <signal.h>
#include <netinet/in.h>
#include <netinet/sctp.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>

#define PORT 11000
#define MSG_SIZE 1000
#define NUMBER_OF_MESSAGES 1000

int sock;
struct sockaddr_in *paddrs[5];
struct sockaddr_in *laddrs[5];

void handle_signal(int signum);

int main(int argc, char **argv)
{
int i;
int counter = 0;
int asconf = 1;
int ret;
int addr_count;
char address[16];
char buffer[MSG_SIZE];
sctp_assoc_t id;
struct sockaddr_in addr;
struct sctp_status status;
struct sctp_initmsg initmsg;
struct sctp_event_subscribe events;
struct sigaction sig_handler;
struct sctp_paddrparams heartbeat;
struct sctp_rtoinfo rtoinfo;

memset(&buffer, 'j', MSG_SIZE);
memset(&initmsg, 0, sizeof(struct sctp_initmsg));
memset(&addr, 0, sizeof(struct sockaddr_in));
memset(&events, 1, sizeof(struct sctp_event_subscribe));
memset(&status, 0, sizeof(struct sctp_status));
memset(&heartbeat, 0, sizeof(struct sctp_paddrparams));
memset(&rtoinfo, 0, sizeof(struct sctp_rtoinfo))

if(argc != 2 || (inet_addr(argv[1]) == -1))
{
puts("Usage: client [IP ADDRESS in form xxx.xxx.xxx.xxx] ");
return 0;
}

strncpy(address, argv[1], 15);
address[15] = 0;

addr.sin_family = AF_INET;
inet_aton(address, &(addr.sin_addr));
addr.sin_port = htons(PORT);

initmsg.sinit_num_ostreams = 2;
initmsg.sinit_max_instreams = 2;
initmsg.sinit_max_attempts = 1;

heartbeat.spp_flags = SPP_HB_ENABLE;
heartbeat.spp_hbinterval = 5000;
heartbeat.spp_pathmaxrxt = 1;

rtoinfo.srto_max = 2000;

sig_handler.sa_handler = handle_signal;
sig_handler.sa_flags = 0;

/*Handle SIGINT in handle_signal Function*/
if(sigaction(SIGINT, &sig_handler, NULL) == -1)
perror("sigaction");

/*Create the Socket*/
if((ret = (sock = socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP))) < 0)
perror("socket");

/*Configure Heartbeats*/
if((ret = setsockopt(sock, SOL_SCTP, SCTP_PEER_ADDR_PARAMS , &heartbeat, sizeof(heartbeat))) != 0)
perror("setsockopt");

/*Set rto_max*/
if((ret = setsockopt(sock, SOL_SCTP, SCTP_RTOINFO , &rtoinfo, sizeof(rtoinfo))) != 0)
perror("setsockopt");

/*Set SCTP Init Message*/
if((ret = setsockopt(sock, SOL_SCTP, SCTP_INITMSG, &initmsg, sizeof(initmsg))) != 0)
perror("setsockopt");

/*Enable SCTP Events*/
if((ret = setsockopt(sock, SOL_SCTP, SCTP_EVENTS, (void *)&events, sizeof(events))) != 0)
perror("setsockopt");

/*Get And Print Heartbeat Interval*/
i = (sizeof heartbeat);
getsockopt(sock, SOL_SCTP, SCTP_PEER_ADDR_PARAMS, &heartbeat, (socklen_t*)&i);

printf("Heartbeat interval %d\n", heartbeat.spp_hbinterval);

/*Connect to Host*/
if(((ret = connect(sock, (struct sockaddr*)&addr, sizeof(struct sockaddr)))) < 0)
{
perror("connect");
close(sock);
exit(0);
}

/*Get Peer Addresses*/
addr_count = sctp_getpaddrs(sock, 0, (struct sockaddr**)paddrs);
printf("\nPeer addresses: %d\n", addr_count);

/*Print Out Addresses*/
for(i = 0; i < addr_count; i++)
printf("Address %d: %s:%d\n", i +1, inet_ntoa((*paddrs)[i].sin_addr), (*paddrs)[i].sin_port);

sctp_freepaddrs((struct sockaddr*)*paddrs);

/*Start to Send Data*/
for(i = 0; i < NUMBER_OF_MESSAGES; i++)
{
counter++;
printf("Sending data chunk #%d...", counter);

if((ret = send(sock, buffer, MSG_SIZE, 0)) == -1)
perror("write");

printf("Sent %d bytes to peer\n",ret);

sleep(1);
}

if(close(sock) != 0)
perror("close");
}


void handle_signal(int signum)
{
switch(signum)
{
case SIGINT:
if(close(sock) != 0)
perror("close");
exit(0);
break;
default: exit(0);
break;
}
}

关于c - SCTP多宿主,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6342617/

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