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