1*4882a593Smuzhiyun /* SPDX-License-Identifier: GPL-2.0 */
2*4882a593Smuzhiyun #ifndef __UM_SLIP_COMMON_H
3*4882a593Smuzhiyun #define __UM_SLIP_COMMON_H
4*4882a593Smuzhiyun
5*4882a593Smuzhiyun #define BUF_SIZE 1500
6*4882a593Smuzhiyun /* two bytes each for a (pathological) max packet of escaped chars + *
7*4882a593Smuzhiyun * terminating END char + initial END char */
8*4882a593Smuzhiyun #define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
9*4882a593Smuzhiyun
10*4882a593Smuzhiyun /* SLIP protocol characters. */
11*4882a593Smuzhiyun #define SLIP_END 0300 /* indicates end of frame */
12*4882a593Smuzhiyun #define SLIP_ESC 0333 /* indicates byte stuffing */
13*4882a593Smuzhiyun #define SLIP_ESC_END 0334 /* ESC ESC_END means END 'data' */
14*4882a593Smuzhiyun #define SLIP_ESC_ESC 0335 /* ESC ESC_ESC means ESC 'data' */
15*4882a593Smuzhiyun
slip_unesc(unsigned char c,unsigned char * buf,int * pos,int * esc)16*4882a593Smuzhiyun static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
17*4882a593Smuzhiyun int *esc)
18*4882a593Smuzhiyun {
19*4882a593Smuzhiyun int ret;
20*4882a593Smuzhiyun
21*4882a593Smuzhiyun switch(c){
22*4882a593Smuzhiyun case SLIP_END:
23*4882a593Smuzhiyun *esc = 0;
24*4882a593Smuzhiyun ret=*pos;
25*4882a593Smuzhiyun *pos=0;
26*4882a593Smuzhiyun return(ret);
27*4882a593Smuzhiyun case SLIP_ESC:
28*4882a593Smuzhiyun *esc = 1;
29*4882a593Smuzhiyun return(0);
30*4882a593Smuzhiyun case SLIP_ESC_ESC:
31*4882a593Smuzhiyun if(*esc){
32*4882a593Smuzhiyun *esc = 0;
33*4882a593Smuzhiyun c = SLIP_ESC;
34*4882a593Smuzhiyun }
35*4882a593Smuzhiyun break;
36*4882a593Smuzhiyun case SLIP_ESC_END:
37*4882a593Smuzhiyun if(*esc){
38*4882a593Smuzhiyun *esc = 0;
39*4882a593Smuzhiyun c = SLIP_END;
40*4882a593Smuzhiyun }
41*4882a593Smuzhiyun break;
42*4882a593Smuzhiyun }
43*4882a593Smuzhiyun buf[(*pos)++] = c;
44*4882a593Smuzhiyun return(0);
45*4882a593Smuzhiyun }
46*4882a593Smuzhiyun
slip_esc(unsigned char * s,unsigned char * d,int len)47*4882a593Smuzhiyun static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
48*4882a593Smuzhiyun {
49*4882a593Smuzhiyun unsigned char *ptr = d;
50*4882a593Smuzhiyun unsigned char c;
51*4882a593Smuzhiyun
52*4882a593Smuzhiyun /*
53*4882a593Smuzhiyun * Send an initial END character to flush out any
54*4882a593Smuzhiyun * data that may have accumulated in the receiver
55*4882a593Smuzhiyun * due to line noise.
56*4882a593Smuzhiyun */
57*4882a593Smuzhiyun
58*4882a593Smuzhiyun *ptr++ = SLIP_END;
59*4882a593Smuzhiyun
60*4882a593Smuzhiyun /*
61*4882a593Smuzhiyun * For each byte in the packet, send the appropriate
62*4882a593Smuzhiyun * character sequence, according to the SLIP protocol.
63*4882a593Smuzhiyun */
64*4882a593Smuzhiyun
65*4882a593Smuzhiyun while (len-- > 0) {
66*4882a593Smuzhiyun switch(c = *s++) {
67*4882a593Smuzhiyun case SLIP_END:
68*4882a593Smuzhiyun *ptr++ = SLIP_ESC;
69*4882a593Smuzhiyun *ptr++ = SLIP_ESC_END;
70*4882a593Smuzhiyun break;
71*4882a593Smuzhiyun case SLIP_ESC:
72*4882a593Smuzhiyun *ptr++ = SLIP_ESC;
73*4882a593Smuzhiyun *ptr++ = SLIP_ESC_ESC;
74*4882a593Smuzhiyun break;
75*4882a593Smuzhiyun default:
76*4882a593Smuzhiyun *ptr++ = c;
77*4882a593Smuzhiyun break;
78*4882a593Smuzhiyun }
79*4882a593Smuzhiyun }
80*4882a593Smuzhiyun *ptr++ = SLIP_END;
81*4882a593Smuzhiyun return (ptr - d);
82*4882a593Smuzhiyun }
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun struct slip_proto {
85*4882a593Smuzhiyun unsigned char ibuf[ENC_BUF_SIZE];
86*4882a593Smuzhiyun unsigned char obuf[ENC_BUF_SIZE];
87*4882a593Smuzhiyun int more; /* more data: do not read fd until ibuf has been drained */
88*4882a593Smuzhiyun int pos;
89*4882a593Smuzhiyun int esc;
90*4882a593Smuzhiyun };
91*4882a593Smuzhiyun
slip_proto_init(struct slip_proto * slip)92*4882a593Smuzhiyun static inline void slip_proto_init(struct slip_proto * slip)
93*4882a593Smuzhiyun {
94*4882a593Smuzhiyun memset(slip->ibuf, 0, sizeof(slip->ibuf));
95*4882a593Smuzhiyun memset(slip->obuf, 0, sizeof(slip->obuf));
96*4882a593Smuzhiyun slip->more = 0;
97*4882a593Smuzhiyun slip->pos = 0;
98*4882a593Smuzhiyun slip->esc = 0;
99*4882a593Smuzhiyun }
100*4882a593Smuzhiyun
101*4882a593Smuzhiyun extern int slip_proto_read(int fd, void *buf, int len,
102*4882a593Smuzhiyun struct slip_proto *slip);
103*4882a593Smuzhiyun extern int slip_proto_write(int fd, void *buf, int len,
104*4882a593Smuzhiyun struct slip_proto *slip);
105*4882a593Smuzhiyun
106*4882a593Smuzhiyun #endif
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