From bf678d54237698a79d41ea3ae49d885f0e83bec4 Mon Sep 17 00:00:00 2001 From: Denis Vlasenko Date: Wed, 9 May 2007 12:50:08 +0000 Subject: [PATCH] tftp: explain "block# 0" codepath; report our decision to bail out to server if blocksize option doesn't look good (it was a FIXME. +33 bytes code); make code more readable. --- networking/tftp.c | 143 +++++++++++++++++++++++----------------------- 1 file changed, 70 insertions(+), 73 deletions(-) diff --git a/networking/tftp.c b/networking/tftp.c index 1f1dfff71..3fb76ecbb 100644 --- a/networking/tftp.c +++ b/networking/tftp.c @@ -37,15 +37,15 @@ #define TFTP_OACK 6 #if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT -#define USE_GETPUT(a) +#define USE_GETPUT(...) #define CMD_GET(cmd) 1 #define CMD_PUT(cmd) 0 #elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT -#define USE_GETPUT(a) +#define USE_GETPUT(...) #define CMD_GET(cmd) 0 #define CMD_PUT(cmd) 1 #else -#define USE_GETPUT(a) a +#define USE_GETPUT(...) __VA_ARGS__ /* masks coming from getpot32 */ #define CMD_GET(cmd) ((cmd) & 1) #define CMD_PUT(cmd) ((cmd) & 2) @@ -109,10 +109,7 @@ static char *tftp_option_get(char *buf, int len, const char *option) #endif -static int tftp( -#if ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT - const int cmd, -#endif +static int tftp( USE_GETPUT(const int cmd,) len_and_sockaddr *peer_lsa, const char *remotefile, const int localfd, unsigned port, int tftp_bufsize) @@ -181,6 +178,9 @@ static int tftp( /* First packet is built, so skip packet generation */ goto send_pkt; + /* Using mostly goto's - continue/break will be less clear + * in where we actually jump to */ + while (1) { /* Build ACK or DATA */ cp = xbuf + 2; @@ -203,67 +203,64 @@ static int tftp( send_pkt: /* Send packet */ *((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */ - timeout = TFTP_NUM_RETRIES; /* re-initialize */ - while (1) { - send_len = cp - xbuf; - /* nb: need to preserve send_len value in code below - * for potential resend! */ + send_len = cp - xbuf; + /* NB: send_len value is preserved in code below + * for potential resend */ send_again: #if ENABLE_DEBUG_TFTP - fprintf(stderr, "sending %u bytes\n", send_len); - for (cp = xbuf; cp < &xbuf[send_len]; cp++) - fprintf(stderr, "%02x ", (unsigned char) *cp); - fprintf(stderr, "\n"); + fprintf(stderr, "sending %u bytes\n", send_len); + for (cp = xbuf; cp < &xbuf[send_len]; cp++) + fprintf(stderr, "%02x ", (unsigned char) *cp); + fprintf(stderr, "\n"); #endif - xsendto(socketfd, xbuf, send_len, &peer_lsa->sa, peer_lsa->len); - /* Was it final ACK? then exit */ - if (finished && (opcode == TFTP_ACK)) - goto ret; + xsendto(socketfd, xbuf, send_len, &peer_lsa->sa, peer_lsa->len); + /* Was it final ACK? then exit */ + if (finished && (opcode == TFTP_ACK)) + goto ret; - /* Receive packet */ + timeout = TFTP_NUM_RETRIES; /* re-initialize */ recv_again: - tv.tv_sec = TFTP_TIMEOUT; - tv.tv_usec = 0; - FD_ZERO(&rfds); - FD_SET(socketfd, &rfds); - switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) { - unsigned from_port; - case 1: - from->len = peer_lsa->len; - memset(&from->sa, 0, peer_lsa->len); - len = recvfrom(socketfd, rbuf, tftp_bufsize, 0, - &from->sa, &from->len); - if (len < 0) { - bb_perror_msg("recvfrom"); - goto ret; - } - from_port = get_nport(&from->sa); - if (port == org_port) { - /* Our first query went to port 69 - * but reply will come from different one. - * Remember and use this new port */ - port = from_port; - set_nport(peer_lsa, from_port); - } - if (port != from_port) - goto recv_again; - goto recvd_good; - case 0: - timeout--; - if (timeout == 0) { - bb_error_msg("last timeout"); - goto ret; - } - bb_error_msg("last timeout" + 5); - goto send_again; /* resend last sent pkt */ - default: - bb_perror_msg("select"); + /* Receive packet */ + tv.tv_sec = TFTP_TIMEOUT; + tv.tv_usec = 0; + FD_ZERO(&rfds); + FD_SET(socketfd, &rfds); + switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) { + unsigned from_port; + case 1: + from->len = peer_lsa->len; + memset(&from->sa, 0, peer_lsa->len); + len = recvfrom(socketfd, rbuf, tftp_bufsize, 0, + &from->sa, &from->len); + if (len < 0) { + bb_perror_msg("recvfrom"); goto ret; } - } /* while we don't see recv packet with correct port# */ - + from_port = get_nport(&from->sa); + if (port == org_port) { + /* Our first query went to port 69 + * but reply will come from different one. + * Remember and use this new port */ + port = from_port; + set_nport(peer_lsa, from_port); + } + if (port != from_port) + goto recv_again; + goto process_pkt; + case 0: + timeout--; + if (timeout == 0) { + bb_error_msg("last timeout"); + goto ret; + } + bb_error_msg("last timeout" + 5); + goto send_again; /* resend last sent pkt */ + default: + bb_perror_msg("select"); + goto ret; + } + process_pkt: /* Process recv'ed packet */ - recvd_good: opcode = ntohs( ((uint16_t*)rbuf)[0] ); recv_blk = ntohs( ((uint16_t*)rbuf)[1] ); @@ -281,9 +278,9 @@ static int tftp( "unknown transfer id", "file already exists", "no such user", + "bad option", }; enum { NUM_ERRCODE = sizeof(errcode_str) / sizeof(errcode_str[0]) }; - const char *msg = ""; if (rbuf[4] != '\0') { @@ -308,8 +305,13 @@ static int tftp( if (res) { int blksize = xatoi_u(res); if (!tftp_blocksize_check(blksize, tftp_bufsize - 4)) { + /* send ERROR 8 to server... */ + /* htons can be impossible to use in const initializer: */ + /*static const uint16_t error_8[2] = { htons(TFTP_ERROR), htons(8) };*/ + /* thus we open-code big-endian layout */ + static const char error_8[4] = { 0,TFTP_ERROR, 0,8 }; + xsendto(socketfd, error_8, 4, &peer_lsa->sa, peer_lsa->len); bb_error_msg("server proposes bad blksize %d, exiting", blksize); - // FIXME: must also send ERROR 8 to server... goto ret; } #if ENABLE_DEBUG_TFTP @@ -317,7 +319,8 @@ static int tftp( blksize); #endif tftp_bufsize = blksize + 4; - block_nr = 0; // TODO: explain why??? + /* Send ACK for OACK ("block" no: 0) */ + block_nr = 0; continue; } /* rfc2347: @@ -430,9 +433,8 @@ int tftp_main(int argc, char **argv) if (!remotefile || !argv[0]) bb_show_usage(); - if (LONE_DASH(localfile)) { - fd = CMD_GET(cmd) ? STDOUT_FILENO : STDIN_FILENO; - } else { + fd = CMD_GET(cmd) ? STDOUT_FILENO : STDIN_FILENO; + if (!LONE_DASH(localfile)) { fd = xopen(localfile, flags); } @@ -440,17 +442,12 @@ int tftp_main(int argc, char **argv) peer_lsa = xhost2sockaddr(argv[0], port); #if ENABLE_DEBUG_TFTP - fprintf(stderr, "using server \"%s\", " - "remotefile \"%s\", localfile \"%s\"\n", + fprintf(stderr, "using server '%s', remotefile '%s', localfile '%s'\n", xmalloc_sockaddr2dotted(&peer_lsa->sa, peer_lsa->len), remotefile, localfile); #endif - result = tftp( -#if ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT - cmd, -#endif - peer_lsa, remotefile, fd, port, blocksize); + result = tftp( USE_GETPUT(cmd,) peer_lsa, remotefile, fd, port, blocksize); if (ENABLE_FEATURE_CLEAN_UP) close(fd);