/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __UM_SLIP_COMMON_H
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#define __UM_SLIP_COMMON_H
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#define BUF_SIZE 1500
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/* two bytes each for a (pathological) max packet of escaped chars + *
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* terminating END char + initial END char */
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#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
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/* SLIP protocol characters. */
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#define SLIP_END 0300 /* indicates end of frame */
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#define SLIP_ESC 0333 /* indicates byte stuffing */
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#define SLIP_ESC_END 0334 /* ESC ESC_END means END 'data' */
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#define SLIP_ESC_ESC 0335 /* ESC ESC_ESC means ESC 'data' */
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static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
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int *esc)
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{
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int ret;
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switch(c){
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case SLIP_END:
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*esc = 0;
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ret=*pos;
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*pos=0;
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return(ret);
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case SLIP_ESC:
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*esc = 1;
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return(0);
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case SLIP_ESC_ESC:
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if(*esc){
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*esc = 0;
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c = SLIP_ESC;
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}
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break;
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case SLIP_ESC_END:
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if(*esc){
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*esc = 0;
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c = SLIP_END;
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}
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break;
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}
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buf[(*pos)++] = c;
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return(0);
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}
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static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
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{
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unsigned char *ptr = d;
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unsigned char c;
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/*
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* Send an initial END character to flush out any
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* data that may have accumulated in the receiver
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* due to line noise.
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*/
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*ptr++ = SLIP_END;
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/*
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* For each byte in the packet, send the appropriate
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* character sequence, according to the SLIP protocol.
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*/
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while (len-- > 0) {
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switch(c = *s++) {
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case SLIP_END:
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*ptr++ = SLIP_ESC;
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*ptr++ = SLIP_ESC_END;
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break;
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case SLIP_ESC:
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*ptr++ = SLIP_ESC;
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*ptr++ = SLIP_ESC_ESC;
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break;
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default:
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*ptr++ = c;
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break;
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}
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}
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*ptr++ = SLIP_END;
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return (ptr - d);
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}
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struct slip_proto {
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unsigned char ibuf[ENC_BUF_SIZE];
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unsigned char obuf[ENC_BUF_SIZE];
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int more; /* more data: do not read fd until ibuf has been drained */
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int pos;
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int esc;
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};
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static inline void slip_proto_init(struct slip_proto * slip)
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{
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memset(slip->ibuf, 0, sizeof(slip->ibuf));
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memset(slip->obuf, 0, sizeof(slip->obuf));
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slip->more = 0;
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slip->pos = 0;
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slip->esc = 0;
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}
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extern int slip_proto_read(int fd, void *buf, int len,
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struct slip_proto *slip);
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extern int slip_proto_write(int fd, void *buf, int len,
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struct slip_proto *slip);
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#endif
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