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Bug Fix in modesReadFromClient()

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The modesReadFromClient() funtion is called from modesReadFromClients(),
which in turn is called from backgroundTasks(). backgroundTasks() is
called from within the main processing loop.

However, modesReadFromClient() can and does block. It attempts to read
characters from the input stream, and loops whilst there was no error.
This stalls the main RTL processing loop until an error occurs. In order
to support simultaneous local reception (via our RTL dongle) and remote
forwarding (data received from the interweb) we cannot allow this
internet read to stall.

To fix this, in modesReadFromClient() attempt to read a buffer of data
(currently 0x400 bytes). If we get a full buffer of bytes, then process
them, and attempt to read another full buffer. Keep doing thios untill
we read only a partial buffer (less than 0x400 bytes). Process the
partial buffer bytes and return.

This allows us to occasionally process data that is arriving from the
internet (which is buffered anyway in the TCP stack), without blocking
local RTL dongle decoding.
This commit is contained in:
Malcolm Robb 2013-09-20 16:48:15 +01:00
parent 52ac50b018
commit 7ea2e8fdef
3 changed files with 59 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

30
net_io.c
View file

@ -759,24 +759,29 @@ void modesReadFromClient(struct client *c, char *sep,
int left;
int nread;
int fullmsg;
int bContinue = 1;
char *s, *e;
while(1) {
while(bContinue) {
fullmsg = 0;
left = MODES_CLIENT_BUF_SIZE - c->buflen;
// If our buffer is full discard it, this is some badly formatted shit
if (left == 0) {
if (left <= 0) {
c->buflen = 0;
left = MODES_CLIENT_BUF_SIZE;
// If there is garbage, read more to discard it ASAP
}
nread = read(c->fd, c->buf+c->buflen, left);
// If we didn't get all the data we asked for, then return once we've processed what we did get.
if (nread != left) {
bContinue = 0;
}
if ( (nread < 0) && (errno != EAGAIN)) { // Error, or end of file
modesFreeClient(c->fd);
}
if (nread <= 0) {
if (nread == 0 || errno != EAGAIN) { // Error, or end of file
modesFreeClient(c->fd);
}
break; // Serve next client
}
c->buflen += nread;
@ -787,12 +792,12 @@ void modesReadFromClient(struct client *c, char *sep,
e = s = c->buf; // Start with the start of buffer, first message
if (c->service == Modes.bis) {
// This is the Bease Binary scanning case.
// This is the Beast Binary scanning case.
// If there is a complete message still in the buffer, there must be the separator 'sep'
// in the buffer, note that we full-scan the buffer at every read for simplicity.
left = c->buflen; // Length of valid search for memchr()
while (left && ((s = memchr(e, (char) 0x1a, left)) != NULL)) { // In reality the first byte of buffer 'should' be 0x1a
while (left && ((s = memchr(e, (char) 0x1a, left)) != NULL)) { // The first byte of buffer 'should' be 0x1a
s++; // skip the 0x1a
if (*s == '1') {
e = s + MODEAC_MSG_BYTES + 8; // point past remainder of message
@ -820,10 +825,11 @@ void modesReadFromClient(struct client *c, char *sep,
s = e; // For the buffer remainder below
} else {
//
// This is the ASCII scanning case, AVR RAW or HTTP at present
// If there is a complete message still in the buffer, there must be the separator 'sep'
// in the buffer, note that we full-scan the buffer at every read for simplicity.
//
while ((e = strstr(s, sep)) != NULL) { // end of first message if found
*e = '\0'; // The handler expects null terminated strings
if (handler(c, s)) { // Pass message to handler.
@ -835,10 +841,10 @@ void modesReadFromClient(struct client *c, char *sep,
}
}
if (fullmsg) { // We processed something - so
c->buflen = &(c->buf[c->buflen]) - s; // The unprocessed buffer length
memmove(c->buf, s, c->buflen); // move what's remaining to the start of the buffer
} else { // If no message was decoded process the next client
if (fullmsg) { // We processed something - so
c->buflen = &(c->buf[c->buflen]) - s; // Update the unprocessed buffer length
memmove(c->buf, s, c->buflen); // Move what's remaining to the start of the buffer
} else { // If no message was decoded process the next client
break;
}
}