40f0bcf9d
Paul Fox
2007-09-06
Subject
fix infinite retry bug. also, reduce per-packet receive timeout to something more reasonable than 5 seconds, and add simple exponential backoff to compensate. improves performance on marginal networks.
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Commit Diff GitHub →
networking/tftp.c+20 -11
| @@ -21,12 +21,12 @@ | |
| #include "libbb.h" | |
| - | |
| #if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT | |
| #define TFTP_BLOCKSIZE_DEFAULT 512 /* according to RFC 1350, don't change */ | |
| - | #define TFTP_TIMEOUT 5 /* seconds */ |
| - | #define TFTP_NUM_RETRIES 5 /* number of retries */ |
| + | #define TFTP_TIMEOUT 50000 /* 50ms, in microseconds */ |
| + | #define TFTP_MAXTIMEOUT 999000 /* about 1 second, in microseconds */ |
| + | #define TFTP_NUM_RETRIES 12 /* number of backed-off retries */ |
| /* opcodes we support */ | |
| #define TFTP_RRQ 1 | |
| @@ -124,7 +124,7 @@ static int tftp( USE_GETPUT(const int cmd,) | |
| uint16_t opcode; | |
| uint16_t block_nr = 1; | |
| uint16_t recv_blk; | |
| - | int timeout = TFTP_NUM_RETRIES; |
| + | int retries, waittime; |
| char *cp; | |
| unsigned org_port; | |
| @@ -206,6 +206,10 @@ static int tftp( USE_GETPUT(const int cmd,) | |
| send_len = cp - xbuf; | |
| /* NB: send_len value is preserved in code below | |
| * for potential resend */ | |
| + | |
| + | retries = TFTP_NUM_RETRIES; /* re-initialize */ |
| + | waittime = TFTP_TIMEOUT; |
| + | |
| send_again: | |
| #if ENABLE_DEBUG_TFTP | |
| fprintf(stderr, "sending %u bytes\n", send_len); | |
| @@ -218,11 +222,10 @@ static int tftp( USE_GETPUT(const int cmd,) | |
| if (finished && (opcode == TFTP_ACK)) | |
| goto ret; | |
| - | timeout = TFTP_NUM_RETRIES; /* re-initialize */ |
| recv_again: | |
| /* Receive packet */ | |
| - | tv.tv_sec = TFTP_TIMEOUT; |
| - | tv.tv_usec = 0; |
| + | tv.tv_sec = 0; |
| + | tv.tv_usec = waittime; |
| FD_ZERO(&rfds); | |
| FD_SET(socketfd, &rfds); | |
| switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) { | |
| @@ -248,12 +251,18 @@ static int tftp( USE_GETPUT(const int cmd,) | |
| goto recv_again; | |
| goto process_pkt; | |
| case 0: | |
| - | timeout--; |
| - | if (timeout == 0) { |
| - | bb_error_msg("last timeout"); |
| + | retries--; |
| + | if (retries == 0) { |
| + | bb_error_msg("timeout"); |
| goto ret; | |
| } | |
| - | bb_error_msg("last timeout" + 5); |
| + | |
| + | /* exponential backoff with limit */ |
| + | waittime += waittime/2; |
| + | if (waittime > TFTP_MAXTIMEOUT) { |
| + | waittime = TFTP_MAXTIMEOUT; |
| + | } |
| + | |
| goto send_again; /* resend last sent pkt */ | |
| default: | |
| bb_perror_msg("select"); | |