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fix infinite retry bug. also, reduce per-packet receive timeout

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to something more reasonable than 5 seconds, and add simple
exponential backoff to compensate.  improves performance on
marginal networks.
This commit is contained in:
Paul Fox 2007-09-06 17:52:22 +00:00
parent dcf9bba3b7
commit 40f0bcf9d3
1 changed files with 20 additions and 11 deletions
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31
networking/tftp.c
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@ -21,12 +21,12 @@
#include "libbb.h" #include "libbb.h"
#if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT #if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
#define TFTP_BLOCKSIZE_DEFAULT 512 /* according to RFC 1350, don't change */ #define TFTP_BLOCKSIZE_DEFAULT 512 /* according to RFC 1350, don't change */
#define TFTP_TIMEOUT 5 /* seconds */ #define TFTP_TIMEOUT 50000 /* 50ms, in microseconds */
#define TFTP_NUM_RETRIES 5 /* number of retries */ #define TFTP_MAXTIMEOUT 999000 /* about 1 second, in microseconds */
#define TFTP_NUM_RETRIES 12 /* number of backed-off retries */
/* opcodes we support */ /* opcodes we support */
#define TFTP_RRQ 1 #define TFTP_RRQ 1
@ -124,7 +124,7 @@ static int tftp( USE_GETPUT(const int cmd,)
uint16_t opcode; uint16_t opcode;
uint16_t block_nr = 1; uint16_t block_nr = 1;
uint16_t recv_blk; uint16_t recv_blk;
int timeout = TFTP_NUM_RETRIES; int retries, waittime;
char *cp; char *cp;
unsigned org_port; unsigned org_port;
@ -206,6 +206,10 @@ static int tftp( USE_GETPUT(const int cmd,)
send_len = cp - xbuf; send_len = cp - xbuf;
/* NB: send_len value is preserved in code below /* NB: send_len value is preserved in code below
* for potential resend */ * for potential resend */
retries = TFTP_NUM_RETRIES; /* re-initialize */
waittime = TFTP_TIMEOUT;
send_again: send_again:
#if ENABLE_DEBUG_TFTP #if ENABLE_DEBUG_TFTP
fprintf(stderr, "sending %u bytes\n", send_len); 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)) if (finished && (opcode == TFTP_ACK))
goto ret; goto ret;
timeout = TFTP_NUM_RETRIES; /* re-initialize */
recv_again: recv_again:
/* Receive packet */ /* Receive packet */
tv.tv_sec = TFTP_TIMEOUT; tv.tv_sec = 0;
tv.tv_usec = 0; tv.tv_usec = waittime;
FD_ZERO(&rfds); FD_ZERO(&rfds);
FD_SET(socketfd, &rfds); FD_SET(socketfd, &rfds);
switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) { switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) {
@ -248,12 +251,18 @@ static int tftp( USE_GETPUT(const int cmd,)
goto recv_again; goto recv_again;
goto process_pkt; goto process_pkt;
case 0: case 0:
timeout--; retries--;
if (timeout == 0) { if (retries == 0) {
bb_error_msg("last timeout"); bb_error_msg("timeout");
goto ret; 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 */ goto send_again; /* resend last sent pkt */
default: default:
bb_perror_msg("select"); bb_perror_msg("select");