1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __UM_SLIP_COMMON_H 3 #define __UM_SLIP_COMMON_H 4 5 #define BUF_SIZE 1500 6 /* two bytes each for a (pathological) max packet of escaped chars + * 7 * terminating END char + initial END char */ 8 #define ENC_BUF_SIZE (2 * BUF_SIZE + 2) 9 10 /* SLIP protocol characters. */ 11 #define SLIP_END 0300 /* indicates end of frame */ 12 #define SLIP_ESC 0333 /* indicates byte stuffing */ 13 #define SLIP_ESC_END 0334 /* ESC ESC_END means END 'data' */ 14 #define SLIP_ESC_ESC 0335 /* ESC ESC_ESC means ESC 'data' */ 15 16 static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos, 17 int *esc) 18 { 19 int ret; 20 21 switch(c){ 22 case SLIP_END: 23 *esc = 0; 24 ret=*pos; 25 *pos=0; 26 return(ret); 27 case SLIP_ESC: 28 *esc = 1; 29 return(0); 30 case SLIP_ESC_ESC: 31 if(*esc){ 32 *esc = 0; 33 c = SLIP_ESC; 34 } 35 break; 36 case SLIP_ESC_END: 37 if(*esc){ 38 *esc = 0; 39 c = SLIP_END; 40 } 41 break; 42 } 43 buf[(*pos)++] = c; 44 return(0); 45 } 46 47 static inline int slip_esc(unsigned char *s, unsigned char *d, int len) 48 { 49 unsigned char *ptr = d; 50 unsigned char c; 51 52 /* 53 * Send an initial END character to flush out any 54 * data that may have accumulated in the receiver 55 * due to line noise. 56 */ 57 58 *ptr++ = SLIP_END; 59 60 /* 61 * For each byte in the packet, send the appropriate 62 * character sequence, according to the SLIP protocol. 63 */ 64 65 while (len-- > 0) { 66 switch(c = *s++) { 67 case SLIP_END: 68 *ptr++ = SLIP_ESC; 69 *ptr++ = SLIP_ESC_END; 70 break; 71 case SLIP_ESC: 72 *ptr++ = SLIP_ESC; 73 *ptr++ = SLIP_ESC_ESC; 74 break; 75 default: 76 *ptr++ = c; 77 break; 78 } 79 } 80 *ptr++ = SLIP_END; 81 return (ptr - d); 82 } 83 84 struct slip_proto { 85 unsigned char ibuf[ENC_BUF_SIZE]; 86 unsigned char obuf[ENC_BUF_SIZE]; 87 int more; /* more data: do not read fd until ibuf has been drained */ 88 int pos; 89 int esc; 90 }; 91 92 static inline void slip_proto_init(struct slip_proto * slip) 93 { 94 memset(slip->ibuf, 0, sizeof(slip->ibuf)); 95 memset(slip->obuf, 0, sizeof(slip->obuf)); 96 slip->more = 0; 97 slip->pos = 0; 98 slip->esc = 0; 99 } 100 101 extern int slip_proto_read(int fd, void *buf, int len, 102 struct slip_proto *slip); 103 extern int slip_proto_write(int fd, void *buf, int len, 104 struct slip_proto *slip); 105 106 #endif 107