Ed32: 【Kiwi】在非Linux的平台弄個Syslogd機制(tbd)

【概念】

在Linux是跑一個叫 syslogd/klogd 的demand去抓取kernel/user-space丟出來的除錯訊息。

printk: kernel space丟出來的除錯訊息
```
printk("<6>Hello, world!\n");
```

syslog: user space丟出來的訊息

#incluse 
openlog(argv[0],LOG_PID,LOG_USER);
syslog(LOG_INFO,"TEST SYSLOG\n");
closelog();

而 busybox 的 syslogd –R選項又可以負責將撈到的除錯訊息往網路(udp port 514)上丟。

syslogd 所支援的命令，摘錄 -N用法。

$ busybox syslogd --help
BusyBox v1.16.0 (2010-02-10 14:33:06 CST) multi-call binary.

Usage: syslogd [OPTIONS]

System logging utility.
Note that this version of syslogd ignores /etc/syslog.conf.

Options:
 -N rotated logs to keep (default:1, max=99, 0=purge)
 -R HOST[:PORT]  Log to IP or hostname on PORT (default PORT=514/UDP)

參考Source code。得知syslogd.c並不是用廣播的方式丟debug message，還是需要指定Server端 IP。

host2sockaddr 負責dns/ip切換
sendto 負責丟message
G.remoteFD 就是 file handle

#if ENABLE_FEATURE_REMOTE_LOG
static int try_to_resolve_remote(void)
{
    if (!G.remoteAddr) {
        unsigned now = monotonic_sec();
        if ((now - G.last_dns_resolve) < DNS_WAIT_SEC)
                return -1;
        G.last_dns_resolve = now;
        G.remoteAddr = host2sockaddr(G.remoteAddrStr, 514);
        if (!G.remoteAddr)                        
	return -1;        
     }
 return socket(G.remoteAddr->u.sa.sa_family, SOCK_DGRAM, 0);
}
#endif
...
#if ENABLE_FEATURE_REMOTE_LOG
if (G.remoteAddrStr) {
        if (-1 == G.remoteFD) {
                G.remoteFD = try_to_resolve_remote();
                if (-1 == G.remoteFD)
                        goto no_luck;
        }
      
        recvbuf[sz] = '\n'; 
       
        sendto(G.remoteFD, recvbuf, sz+1, MSG_DONTWAIT,
               &G.remoteAddr->u.sa, G.remoteAddr->len);
 no_luck: ;
}
#endif

先以Linux實作(參考: http://www.abc.se/~m6695/udp.html)

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <errno.h>

#define BUFLEN    512
#define NPACK    2
#define PORT    514

#define SRV_IP "192.168.0.105"

void err_msg(char *s)
{
  perror(s);
  exit(1);
}

int main(void)
{
 struct sockaddr_in si_other;
 int s, i, slen=sizeof(si_other);
 char buf[BUFLEN];

 if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
    err_msg("socket");

 memset((char *) &si_other, 0, sizeof(si_other));
 si_other.sin_family = AF_INET;
 si_other.sin_port = htons(PORT);
 if (inet_aton(SRV_IP, &si_other.sin_addr)==0) {
    fprintf(stderr, "inet_aton() failed\n");
    exit(1);
 }

 for (i=0; i<NPACK; i++) {
    printf("Sending packet %d\n", i);
    sprintf(buf, "This is packet %d\n", i);
    if (sendto(s, buf, strlen(buf), 0, &si_other, slen)==-1)
        err_msg("sendto()");
 }

 close(s);
 return 0;
}

結果，將Filter選項設成 syslog
實作考量
1. 能參考那邊的機制: printr/FileConsolePutChar
2. 有需要作一個fifo的機制嗎，一次塞一個char，