hdlc.c (4283B)
1 #include <u.h> 2 #include <libc.h> 3 #include <ip.h> 4 #include "dat.h" 5 #include "protos.h" 6 7 enum { 8 HDLC_frame= 0x7e, 9 HDLC_esc= 0x7d, 10 11 /* PPP frame fields */ 12 PPP_addr= 0xff, 13 PPP_ctl= 0x3, 14 PPP_initfcs= 0xffff, 15 PPP_goodfcs= 0xf0b8 16 }; 17 18 /* 19 * Calculate FCS - rfc 1331 20 */ 21 ushort fcstab[256] = 22 { 23 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 24 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 25 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 26 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 27 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 28 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, 29 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 30 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, 31 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, 32 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 33 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 34 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 35 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 36 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 37 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, 38 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 39 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 40 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, 41 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 42 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 43 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 44 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 45 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 46 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, 47 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 48 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, 49 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 50 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 51 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 52 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 53 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 54 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 55 }; 56 57 static uchar inbuf[16*1024]; 58 static int inlen; 59 60 static Mux p_mux[] = 61 { 62 {"ppp", (PPP_addr<<8)|PPP_ctl, } , 63 {0} 64 }; 65 66 enum 67 { 68 Ot = 1 69 }; 70 71 static void 72 p_compile(Filter *f) 73 { 74 Mux *m; 75 76 for(m = p_mux; m->name != nil; m++) 77 if(strcmp(f->s, m->name) == 0){ 78 f->pr = m->pr; 79 f->ulv = m->val; 80 f->subop = Ot; 81 return; 82 } 83 sysfatal("unknown ethernet field or protocol: %s", f->s); 84 } 85 86 static int 87 p_filter(Filter *f, Msg *m) 88 { 89 ulong t; 90 91 if(m->pe-m->ps < 2) 92 return 0; 93 94 switch(f->subop){ 95 case Ot: 96 t = (m->ps[0]<<8)|m->ps[1]; 97 if(t != f->ulv) 98 return 0; 99 break; 100 } 101 return 1; 102 } 103 104 static int 105 p_seprint(Msg *m) 106 { 107 ulong t; 108 109 if(m->pe-m->ps < 2) 110 return -1; 111 112 t = (m->ps[0]<<8)|m->ps[1]; 113 m->ps += 2; 114 demux(p_mux, t, t, m, &dump); 115 116 return 0; 117 } 118 119 static int 120 p_framer(int fd, uchar *pkt, int pktlen) 121 { 122 ushort fcs; 123 uchar *from, *efrom, *to, *eto; 124 int n; 125 ulong c; 126 127 eto = pkt+pktlen; 128 for(;;){ 129 efrom = memchr(inbuf, HDLC_frame, inlen); 130 if(efrom == nil){ 131 if(inlen >= sizeof(inbuf)) 132 inlen = 0; 133 n = read(fd, inbuf+inlen, sizeof(inbuf)-inlen); 134 if(n <= 0) 135 break; 136 inlen += n; 137 continue; 138 } 139 140 /* checksum and unescape the frame */ 141 fcs = PPP_initfcs; 142 to = pkt; 143 for(from = inbuf; from < efrom;){ 144 c = *from++; 145 if(c == HDLC_esc) 146 c = (*from++) ^ 0x20; 147 if(to < eto) 148 *to++ = c; 149 fcs = (fcs >> 8) ^ fcstab[(fcs ^ c) & 0xff]; 150 } 151 152 /* move down anything that's left */ 153 inlen -= efrom+1-inbuf; 154 memmove(inbuf, efrom+1, inlen); 155 156 /* accept if this is a good packet */ 157 if(fcs != PPP_goodfcs) 158 print("bad frame %ld %2.2ux %2.2ux!\n", to-pkt, pkt[0], pkt[1]); 159 else 160 return to-pkt; 161 } 162 return -1; 163 } 164 165 Proto hdlc = 166 { 167 "hdlc", 168 p_compile, 169 p_filter, 170 p_seprint, 171 p_mux, 172 "%#.4lux", 173 nil, 174 p_framer 175 };