/* * ppphdlc.c * * Allows linux pppd to run on top of generic hdlc sync interfaces * Requirements: hdlcX needs to be down before calling ppphdlc (ifconfig hdlcX down) * Design principle is maximum simplicity, don't duplicate any functionality * already available with pppd and use as little as possible from sync card as well, * just plain framing * * Bare bones example, assume interface is hdlc0: * modprobe pc300too # That's for a Cyclades PC300 * modprobe hdlc_raw # That's for plain HDLC protocol * pppd receive-all pty "ifconfig hdlc0 down; exec ppphdlc hdlc0" * * receive-all is a must, otherwise pppd will discard all incoming frames and won't connect * Sync interfaces are always binary transparent ! * * All compression, encryption, authentication, routing, scripting, multilink and multiprotocol * features of pppd should work just fine. I'm using ipv4 with deflate compression in production, and it works perfectly * * ppphdlc will automatically set the sync interface to hdlc protocol, default line coding (typically nrz), no-crc * CRC generation/checking is done in pppd * It doesn't use any ppp features of generic HDLC, *all* ppp processing happens on pppd * * This code is linux specific, uses epoll (requires linux 2.6.x), it looks like generic hdlc is linux specific anyhow * * Forget about the sync option of pppd, it will cause framing errors under load * Anyways, this code won't work at all with pppd sync option ! * * Sugest compiling with -Os, since modern processors are cache bound anyways * gcc -o ppphdlc -Os ppphdlc.c * * This tool is in production. It works. But use at your own risk. * * Copyright (C) 2010 Marcelo Pacheco * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* typedef unsigned short u16; typedef unsigned char u8; u16 const crc_ccitt_table[256] = { 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 }; #define PPP_INITFCS 0xffff // Initial FCS value #define PPP_GOODFCS 0xf0b8 // Good final FCS value static inline u16 PPP_FCS(u16 crc, const u8 c) { return (crc >> 8) ^ crc_ccitt_table[(crc ^ c) & 0xff]; } */ #define PPP_FLAG 0x7e #define PPP_ESCAPE 0x7d /* PPP_ESPACE is followed by the original character XOR 0x20 */ #define CTRL_XOR 0x20 int sock; int startup(int argc, char *argv[]) { struct ifreq ifr; int if_sock; struct sockaddr_ll addr; raw_hdlc_proto raw; if (argc != 2) { dprintf(2, "Syntax: ppphdlc hdlcX\n" " Copyright Marcelo Pacheco - marcelo@m2j.com.br - 2010\n"); return (1); } strcpy(ifr.ifr_name, argv[1]); if ((if_sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP)) < 0) { dprintf(2, "socket: %d", errno); return (2); } memset(&raw, 0, sizeof(raw)); raw.encoding = ENCODING_DEFAULT; // Use no CRC at the driver level, we pass CRCs from pppd through raw.parity = PARITY_NONE; ifr.ifr_settings.type = IF_PROTO_HDLC; ifr.ifr_settings.ifs_ifsu.raw_hdlc = &raw; ifr.ifr_settings.size = sizeof(raw); if (ioctl(if_sock, SIOCWANDEV, &ifr)) { dprintf(2, "ioctl %d\n", errno); return (3); } if (ioctl(if_sock, SIOCGIFFLAGS, &ifr)) { dprintf(2, "ioctl SIOCGIFFLAGS %d\n", errno); return (4); } ifr.ifr_flags |= (IFF_UP | IFF_RUNNING); if (ioctl(if_sock, SIOCSIFFLAGS, &ifr)) { dprintf(2, "ioctl SIOCSIFFLAGS %d\n", errno); return (5); } if (ioctl(if_sock, SIOCGIFINDEX, &ifr)) { dprintf(2, "ioctl SIOCGIFINDEX %d\n", errno); return (6); } memset(&addr, 0, sizeof(addr)); addr.sll_family = AF_PACKET; addr.sll_protocol = htons(ETH_P_ALL); addr.sll_ifindex = ifr.ifr_ifindex; if ((sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))) < 0 || bind(sock, (struct sockaddr*)&addr, sizeof(addr)) < 0) { dprintf(2, "socket/bind %d\n", errno); return(7); } return 0; } #define PUT_BYTE(p) if ((p) == PPP_FLAG || (p) == PPP_ESCAPE) *p1++ = PPP_ESCAPE, *p1++ = (p) ^ CTRL_XOR; else *p1++ = (p); static inline int sync2async() { int ret /*, fcs */; char *p, // Input pointer *p1, // Output pointer *p2, // p2 = The end of the input message and beginning of the output message buf[4096]; // Once packet received, uses the rest of the buffer for output (escaped) message /* We get exactly one PPP packet per hdlc message */ if ((ret = read(sock, buf, sizeof(buf))) > 0) { //fcs = PPP_INITFCS; p = buf; p2 = p1 = buf + ret; while (p < p2) { PUT_BYTE(*p); // fcs = PPP_FCS(fcs, *p); p++; } /* fcs = ~fcs; ret = fcs & 0xff; PUT_BYTE(ret); ret = (fcs >> 8) & 0xff; PUT_BYTE(ret); */ *p1++ = PPP_FLAG; if ((ret = write(1, p2, p1 - p2)) != p1 - p2) { dprintf(2, "write 1 sz: %d ret: %d errno: %d\n", p2 - p1, ret, errno); return 0; } return 1; } else return 0; } int main(int argc, char *argv[]) { int ret, epfd; struct epoll_event ev; char buf[4096], // Receive buffer buf1[1530], // Store the un-escaped de-flagged message to be sent here *p, // Processing pointer into buf *p1, // Receive pointer *p2; // Processing pointer into buf1 ret = startup(argc, argv); if (ret) return ret; if ( (epfd = epoll_create(3)) < 0 ) return 0x20; ev.events = EPOLLIN | EPOLLERR | EPOLLHUP; ev.data.fd = sock; epoll_ctl(epfd, EPOLL_CTL_ADD, sock, &ev); ev.events = EPOLLIN | EPOLLERR | EPOLLHUP; ev.data.fd = 0; epoll_ctl(epfd, EPOLL_CTL_ADD, 0, &ev); p1 = p = buf, p2 = buf1; while (1) { if (epoll_wait(epfd, &ev, 1, -1) <= 0) continue; else if (ev.data.fd == sock) { if (ev.events & EPOLLHUP) return 0x10; if (ev.events & EPOLLERR) dprintf(2, "hdlcX err\n"); if (ev.events & EPOLLIN) if (!sync2async()) return 0x11; } else if (ev.data.fd == 0) { if (ev.events & EPOLLHUP) return 0xf; if (ev.events & EPOLLERR) dprintf(2, "0 err\n"); if (ev.events & EPOLLIN) if ( (ret = read(0, p1, buf + sizeof(buf) - p1)) > 0 ) { p1 += ret; while (p < p1) switch (*p) { case PPP_FLAG: p++; if (p2 > buf1 && // Only forward non empty packets (ret = write(sock, buf1, p2 - buf1)) != p2 - buf1) { if (errno != ENOBUFS) // ENOBUFS=lost packet, can happen, ignore, otherwise bomb out { dprintf(2, "write hdlcX sz: %d ret: %d errno: %d\n", p2 - buf1, ret, errno); return 0x10; } // usleep(100000); // Sleep 100msec, then try again, just enough to send 800 bytes @ 64kbps } p2 = buf1; break; case PPP_ESCAPE: if (p1 - p == 1) // The escaped character isn't in the receive buffer yet { *buf = *p; // The receive buffer has only one char, move that to the beginning p = p1 = buf; p1++; // Advance the read pointer by that one character, the ESCAPE character goto read_more; // Need more stuff in the receive buffer before continuing } p++, *p2++ = *p++ ^ CTRL_XOR; // Skip the ESCAPE break; default: *p2++ = *p++; // Any other char, just copy it } p1 = p = buf; // Receive buffer empty, point to the beginning read_more: ; } else { dprintf(2, "read 0 err: %d errno: %d\n", ret, errno); return 0xf; } } } return 0xe; }