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pkt-line: share buffer/descriptor reading implementation

The packet_read function reads from a descriptor. The
packet_get_line function is similar, but reads from an
in-memory buffer, and uses a completely separate
implementation. This patch teaches the generic packet_read
function to accept either source, and we can do away with
packet_get_line's implementation.

There are two other differences to account for between the
old and new functions. The first is that we used to read
into a strbuf, but now read into a fixed size buffer. The
only two callers are fine with that, and in fact it
simplifies their code, since they can use the same
static-buffer interface as the rest of the packet_read_line
callers (and we provide a similar convenience wrapper for
reading from a buffer rather than a descriptor).

This is technically an externally-visible behavior change in
that we used to accept arbitrary sized packets up to 65532
bytes, and now cap out at LARGE_PACKET_MAX, 65520. In
practice this doesn't matter, as we use it only for parsing
smart-http headers (of which there is exactly one defined,
and it is small and fixed-size). And any extension headers
would be breaking the protocol to go over LARGE_PACKET_MAX
anyway.

The other difference is that packet_get_line would return
on error rather than dying. However, both callers of
packet_get_line are actually improved by dying.

The first caller does its own error checking, but we can
drop that; as a result, we'll actually get more specific
reporting about protocol breakage when packet_read dies
internally. The only downside is that packet_read will not
print the smart-http URL that failed, but that's not a big
deal; anybody not debugging can already see the remote's URL
already, and anybody debugging would want to run with
GIT_CURL_VERBOSE anyway to see way more information.

The second caller, which is just trying to skip past any
extra smart-http headers (of which there are none defined,
but which we allow to keep room for future expansion), did
not error check at all. As a result, it would treat an error
just like a flush packet. The resulting mess would generally
cause an error later in get_remote_heads, but now we get
error reporting much closer to the source of the problem.

Brown-paper-bag-fixes-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
tags/v1.8.3-rc0
Jeff King Junio C Hamano 7 years ago
parent
commit
4981fe750b
6 changed files with 69 additions and 59 deletions
  1. +2
    -1
      connect.c
  2. +1
    -1
      daemon.c
  3. +38
    -38
      pkt-line.c
  4. +17
    -6
      pkt-line.h
  5. +10
    -12
      remote-curl.c
  6. +1
    -1
      sideband.c

+ 2
- 1
connect.c View File

@@ -76,7 +76,8 @@ struct ref **get_remote_heads(int in, struct ref **list,
int len, name_len;
char *buffer = packet_buffer;

len = packet_read(in, packet_buffer, sizeof(packet_buffer),
len = packet_read(in, NULL, NULL,
packet_buffer, sizeof(packet_buffer),
PACKET_READ_GENTLE_ON_EOF |
PACKET_READ_CHOMP_NEWLINE);
if (len < 0)


+ 1
- 1
daemon.c View File

@@ -612,7 +612,7 @@ static int execute(void)
loginfo("Connection from %s:%s", addr, port);

alarm(init_timeout ? init_timeout : timeout);
pktlen = packet_read(0, packet_buffer, sizeof(packet_buffer), 0);
pktlen = packet_read(0, NULL, NULL, packet_buffer, sizeof(packet_buffer), 0);
alarm(0);

len = strlen(line);


+ 38
- 38
pkt-line.c View File

@@ -104,12 +104,28 @@ void packet_buf_write(struct strbuf *buf, const char *fmt, ...)
strbuf_add(buf, buffer, n);
}

static int safe_read(int fd, void *buffer, unsigned size, int options)
static int get_packet_data(int fd, char **src_buf, size_t *src_size,
void *dst, unsigned size, int options)
{
ssize_t ret = read_in_full(fd, buffer, size);
if (ret < 0)
die_errno("read error");
else if (ret < size) {
ssize_t ret;

if (fd >= 0 && src_buf && *src_buf)
die("BUG: multiple sources given to packet_read");

/* Read up to "size" bytes from our source, whatever it is. */
if (src_buf && *src_buf) {
ret = size < *src_size ? size : *src_size;
memcpy(dst, *src_buf, ret);
*src_buf += ret;
*src_size -= ret;
} else {
ret = read_in_full(fd, dst, size);
if (ret < 0)
die_errno("read error");
}

/* And complain if we didn't get enough bytes to satisfy the read. */
if (ret < size) {
if (options & PACKET_READ_GENTLE_ON_EOF)
return -1;

@@ -144,12 +160,13 @@ static int packet_length(const char *linelen)
return len;
}

int packet_read(int fd, char *buffer, unsigned size, int options)
int packet_read(int fd, char **src_buf, size_t *src_len,
char *buffer, unsigned size, int options)
{
int len, ret;
char linelen[4];

ret = safe_read(fd, linelen, 4, options);
ret = get_packet_data(fd, src_buf, src_len, linelen, 4, options);
if (ret < 0)
return ret;
len = packet_length(linelen);
@@ -162,7 +179,7 @@ int packet_read(int fd, char *buffer, unsigned size, int options)
len -= 4;
if (len >= size)
die("protocol error: bad line length %d", len);
ret = safe_read(fd, buffer, len, options);
ret = get_packet_data(fd, src_buf, src_len, buffer, len, options);
if (ret < 0)
return ret;

@@ -175,41 +192,24 @@ int packet_read(int fd, char *buffer, unsigned size, int options)
return len;
}

char *packet_read_line(int fd, int *len_p)
static char *packet_read_line_generic(int fd,
char **src, size_t *src_len,
int *dst_len)
{
int len = packet_read(fd, packet_buffer, sizeof(packet_buffer),
int len = packet_read(fd, src, src_len,
packet_buffer, sizeof(packet_buffer),
PACKET_READ_CHOMP_NEWLINE);
if (len_p)
*len_p = len;
if (dst_len)
*dst_len = len;
return len ? packet_buffer : NULL;
}

int packet_get_line(struct strbuf *out,
char **src_buf, size_t *src_len)
char *packet_read_line(int fd, int *len_p)
{
int len;

if (*src_len < 4)
return -1;
len = packet_length(*src_buf);
if (len < 0)
return -1;
if (!len) {
*src_buf += 4;
*src_len -= 4;
packet_trace("0000", 4, 0);
return 0;
}
if (*src_len < len)
return -2;

*src_buf += 4;
*src_len -= 4;
len -= 4;
return packet_read_line_generic(fd, NULL, NULL, len_p);
}

strbuf_add(out, *src_buf, len);
*src_buf += len;
*src_len -= len;
packet_trace(out->buf, out->len, 0);
return len;
char *packet_read_line_buf(char **src, size_t *src_len, int *dst_len)
{
return packet_read_line_generic(-1, src, src_len, dst_len);
}

+ 17
- 6
pkt-line.h View File

@@ -25,9 +25,16 @@ void packet_buf_flush(struct strbuf *buf);
void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));

/*
* Read a packetized line from the descriptor into the buffer, which must be at
* least size bytes long. The return value specifies the number of bytes read
* into the buffer.
* Read a packetized line into the buffer, which must be at least size bytes
* long. The return value specifies the number of bytes read into the buffer.
*
* If src_buffer is not NULL (and nor is *src_buffer), it should point to a
* buffer containing the packet data to parse, of at least *src_len bytes.
* After the function returns, src_buf will be incremented and src_len
* decremented by the number of bytes consumed.
*
* If src_buffer (or *src_buffer) is NULL, then data is read from the
* descriptor "fd".
*
* If options does not contain PACKET_READ_GENTLE_ON_EOF, we will die under any
* of the following conditions:
@@ -50,7 +57,8 @@ void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((f
*/
#define PACKET_READ_GENTLE_ON_EOF (1u<<0)
#define PACKET_READ_CHOMP_NEWLINE (1u<<1)
int packet_read(int fd, char *buffer, unsigned size, int options);
int packet_read(int fd, char **src_buffer, size_t *src_len, char
*buffer, unsigned size, int options);

/*
* Convenience wrapper for packet_read that is not gentle, and sets the
@@ -61,11 +69,14 @@ int packet_read(int fd, char *buffer, unsigned size, int options);
*/
char *packet_read_line(int fd, int *size);

/*
* Same as packet_read_line, but read from a buf rather than a descriptor;
* see packet_read for details on how src_* is used.
*/
char *packet_read_line_buf(char **src_buf, size_t *src_len, int *size);

#define DEFAULT_PACKET_MAX 1000
#define LARGE_PACKET_MAX 65520
extern char packet_buffer[LARGE_PACKET_MAX];

int packet_get_line(struct strbuf *out, char **src_buf, size_t *src_len);

#endif

+ 10
- 12
remote-curl.c View File

@@ -138,28 +138,26 @@ static struct discovery* discover_refs(const char *service)
if (maybe_smart &&
(5 <= last->len && last->buf[4] == '#') &&
!strbuf_cmp(&exp, &type)) {
char *line;

/*
* smart HTTP response; validate that the service
* pkt-line matches our request.
*/
if (packet_get_line(&buffer, &last->buf, &last->len) <= 0)
die("%s has invalid packet header", refs_url);
if (buffer.len && buffer.buf[buffer.len - 1] == '\n')
strbuf_setlen(&buffer, buffer.len - 1);
line = packet_read_line_buf(&last->buf, &last->len, NULL);

strbuf_reset(&exp);
strbuf_addf(&exp, "# service=%s", service);
if (strbuf_cmp(&exp, &buffer))
die("invalid server response; got '%s'", buffer.buf);
if (strcmp(line, exp.buf))
die("invalid server response; got '%s'", line);
strbuf_release(&exp);

/* The header can include additional metadata lines, up
* until a packet flush marker. Ignore these now, but
* in the future we might start to scan them.
*/
strbuf_reset(&buffer);
while (packet_get_line(&buffer, &last->buf, &last->len) > 0)
strbuf_reset(&buffer);
while (packet_read_line_buf(&last->buf, &last->len, NULL))
;

last->proto_git = 1;
}
@@ -308,7 +306,7 @@ static size_t rpc_out(void *ptr, size_t eltsize,

if (!avail) {
rpc->initial_buffer = 0;
avail = packet_read(rpc->out, rpc->buf, rpc->alloc, 0);
avail = packet_read(rpc->out, NULL, NULL, rpc->buf, rpc->alloc, 0);
if (!avail)
return 0;
rpc->pos = 0;
@@ -425,7 +423,7 @@ static int post_rpc(struct rpc_state *rpc)
break;
}

n = packet_read(rpc->out, buf, left, 0);
n = packet_read(rpc->out, NULL, NULL, buf, left, 0);
if (!n)
break;
rpc->len += n;
@@ -579,7 +577,7 @@ static int rpc_service(struct rpc_state *rpc, struct discovery *heads)
rpc->hdr_accept = strbuf_detach(&buf, NULL);

while (!err) {
int n = packet_read(rpc->out, rpc->buf, rpc->alloc, 0);
int n = packet_read(rpc->out, NULL, NULL, rpc->buf, rpc->alloc, 0);
if (!n)
break;
rpc->pos = 0;


+ 1
- 1
sideband.c View File

@@ -38,7 +38,7 @@ int recv_sideband(const char *me, int in_stream, int out)

while (1) {
int band, len;
len = packet_read(in_stream, buf + pf, LARGE_PACKET_MAX, 0);
len = packet_read(in_stream, NULL, NULL, buf + pf, LARGE_PACKET_MAX, 0);
if (len == 0)
break;
if (len < 1) {


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