waitport.c (3839B)
1 #include <unistd.h> 2 #include <errmsg.h> 3 #include <time.h> 4 #include <string.h> 5 #include <fcntl.h> 6 #include <ctype.h> 7 8 #include <libowfat/fmt.h> 9 #include <libowfat/scan.h> 10 #include <libowfat/ip4.h> 11 #include <libowfat/ip6.h> 12 #include <libowfat/stralloc.h> 13 #include <libowfat/buffer.h> 14 15 static int netstat(const char* addr,unsigned int wantedport) { 16 /* see linux/Documentation/networking/proc_net_tcp.txt */ 17 int fd=-1; 18 char rbuf[4096]; /* since these files can become arbitrarily large, we'll use a real buffer to read from them */ 19 const char* filenames[] = { "/proc/net/tcp6", "/proc/net/tcp" }; 20 buffer b; 21 unsigned int fn; 22 stralloc line; 23 24 for (fn=0; fn<sizeof(filenames)/sizeof(filenames[0]); ++fn) { 25 const char* filename=filenames[fn]; 26 27 fd=open(filename,O_RDONLY|O_CLOEXEC); 28 if (fd==-1) 29 continue; 30 buffer_init(&b,read,fd,rbuf,sizeof(rbuf)); /* can't fail */ 31 for (;;) { 32 int r; 33 char* c; 34 char* local; 35 int v6; 36 stralloc_zero(&line); 37 if ((r=buffer_getline_sa(&b,&line))==-1) { 38 close(fd); 39 die(1,"read error from ",filename); 40 } 41 if (r==0) break; 42 if (line.len < 1 || line.s[line.len-1]!='\n') { 43 parseerror: 44 close(fd); 45 die(1,"parse error in ",filename); 46 } 47 line.s[line.len-1]=0; /* string is now null terminated */ 48 49 /* First token is something like "917:", skip */ 50 for (c=line.s; *c && *c!=':'; ++c) ; 51 if (*c != ':') continue; /* first line is boilerplate text and has no :-token, skip it */ 52 ++c; 53 for (; *c==' '; ++c) ; 54 /* Next token is something like "00000000:1770" or "00000000000000000000000000000000:0016" */ 55 local=c; 56 for (; isxdigit(*c); ++c) ; 57 if (c-local != 8 && c-local != 32) /* we only support ipv4 and ipv6; this is neither */ 58 continue; 59 v6=(c-local==32); 60 if (*c!=':') goto parseerror; 61 for (r=1; r<5; ++r) { 62 if (!isxdigit(c[r])) goto parseerror; 63 } 64 if (c[5]!=' ') goto parseerror; 65 c[5]=0; 66 c+=6; 67 /* Next token is the same thing, but we don't really need it, so 68 * just skip till next whitespace */ 69 for (; *c && *c!=' '; ++c) ; 70 if (*c!=' ') goto parseerror; 71 ++c; 72 /* Next is the state; if we are looking at tcp, 0A means LISTEN */ 73 if (filename[10]=='t' && c[0]=='0' && c[1]=='A') { 74 /* TCP LISTEN */ 75 size_t n; 76 union { 77 char ip[16]; 78 uint32_t ints[4]; 79 } omgwtfbbq; 80 char ipstring[FMT_IP6]; 81 unsigned short port; 82 unsigned long temp; 83 84 /* we can only be here if the hex string is 8 or 32 bytes long, see above */ 85 for (n=0; n<(unsigned int)v6*3+1; ++n) { 86 scan_xlongn(local+n*8,8,&temp); 87 omgwtfbbq.ints[n]=temp; 88 } 89 90 if (scan_xshort(local+(((unsigned int)v6*3+1)*8)+1,&port)!=4) /* can't happen, we validated with isxdigit */ 91 goto parseerror; 92 93 ipstring[v6 ? fmt_ip6c(ipstring,omgwtfbbq.ip) : fmt_ip4(ipstring,omgwtfbbq.ip)]=0; 94 95 if (!strcmp(ipstring,addr?addr : (v6?"::":"0.0.0.0")) && port==wantedport) { 96 close(fd); 97 return 1; 98 } 99 100 } 101 } 102 close(fd); 103 fd=-1; 104 } 105 106 return 0; 107 } 108 109 int main(int argc,char* argv[],char* envp[]) { 110 unsigned short port; 111 112 unsigned int i; 113 struct timespec req,rem; 114 115 char* s=argv[1]; 116 char* t=strchr(s,'/'); 117 118 errmsg_iam("waitport"); 119 if (argc<2) 120 usage: 121 die(0,"usage: waitport ::/111 some.rpcd\n\twaits for a service to bind to TCP port 111 on ::, then executes the rest of the command line"); 122 123 { 124 if (t) { 125 *t=0; 126 if (scan_ushort(t+1,&port)==0) goto usage; 127 } else { 128 if (scan_ushort(s,&port)==0) goto usage; 129 s=0; 130 } 131 } 132 133 req.tv_sec=0; req.tv_nsec=100000000; 134 for (i=0; i<1000; ++i) { 135 if (netstat(s,port)) { 136 if (argv[2]) { 137 execve(argv[2],argv+2,envp); 138 diesys(1,"execve"); 139 } 140 return 0; 141 } 142 nanosleep(&req,&rem); 143 } 144 die(1,"service on port not showing up"); 145 }