Jeff King <peff@xxxxxxxx> writes:
> So something like this. It turned out to be a lot uglier than I had
> hoped because we get fed the data from curl in odd-sized chunks, so we
> need a state machine.
It is unfortunate that we have to snoop the protocol like this to
infer an error, but I do not think we can do better than that
approach. FWIW, I did not find the logic in update_pktline_state()
you wrote ugly at all.
Having to assume that the end of each round from the other end must
be a FLUSH does feel somewhat ugly and brittle, though.
> diff --git a/remote-curl.c b/remote-curl.c
> index f14c41f4c..605357d77 100644
> --- a/remote-curl.c
> +++ b/remote-curl.c
> @@ -403,6 +403,18 @@ struct rpc_state {
> struct strbuf result;
> unsigned gzip_request : 1;
> unsigned initial_buffer : 1;
> +
> + enum {
> + RPC_PKTLINE_ERROR, /* bogus hex chars in length */
> + RPC_PKTLINE_INITIAL, /* no packets received yet */
> + RPC_PKTLINE_1, /* got one hex char */
> + RPC_PKTLINE_2, /* got two hex chars */
> + RPC_PKTLINE_3, /* got three hex chars */
> + RPC_PKTLINE_DATA, /* reading data; pktline_len holds remaining */
> + RPC_PKTLINE_END_OF_PACKET, /* last packet completed */
> + RPC_PKTLINE_FLUSH, /* last packet was flush */
> + } pktline_state;
> + size_t pktline_len;
> };
>
> static size_t rpc_out(void *ptr, size_t eltsize,
> @@ -451,11 +463,77 @@ static curlioerr rpc_ioctl(CURL *handle, int cmd, void *clientp)
> }
> #endif
>
> +static void update_pktline_state(struct rpc_state *rpc,
> + const char *buf, size_t len)
> +{
> +#define READ_ONE_HEX(shift) do { \
> + int val = hexval(buf[0]); \
> + if (val < 0) { \
> + warning("error on %d", *buf); \
> + rpc->pktline_state = RPC_PKTLINE_ERROR; \
> + return; \
> + } \
> + rpc->pktline_len |= val << shift; \
> + buf++; \
> + len--; \
> +} while(0)
> +
> + while (len > 0) {
> + switch (rpc->pktline_state) {
> + case RPC_PKTLINE_ERROR:
> + /* previous error; there is no recovery */
> + return;
> +
> + /* We can start a new pktline at any of these states */
> + case RPC_PKTLINE_INITIAL:
> + case RPC_PKTLINE_FLUSH:
> + case RPC_PKTLINE_END_OF_PACKET:
> + rpc->pktline_len = 0;
> + READ_ONE_HEX(12);
> + rpc->pktline_state = RPC_PKTLINE_1;
> + break;
> +
> + case RPC_PKTLINE_1:
> + READ_ONE_HEX(8);
> + rpc->pktline_state = RPC_PKTLINE_2;
> + break;
> +
> + case RPC_PKTLINE_2:
> + READ_ONE_HEX(4);
> + rpc->pktline_state = RPC_PKTLINE_3;
> + break;
> +
> + case RPC_PKTLINE_3:
> + READ_ONE_HEX(0);
> + if (rpc->pktline_len) {
> + rpc->pktline_state = RPC_PKTLINE_DATA;
> + rpc->pktline_len -= 4;
> + } else
> + rpc->pktline_state = RPC_PKTLINE_FLUSH;
> + break;
> +
> + case RPC_PKTLINE_DATA:
> + if (len < rpc->pktline_len) {
> + rpc->pktline_len -= len;
> + len = 0;
> + } else {
> + buf += rpc->pktline_len;
> + len -= rpc->pktline_len;
> + rpc->pktline_len = 0;
> + rpc->pktline_state = RPC_PKTLINE_END_OF_PACKET;
> + }
> + break;
> + }
> + }
> +#undef READ_ONE_HEX
> +}
> +
> static size_t rpc_in(char *ptr, size_t eltsize,
> size_t nmemb, void *buffer_)
> {
> size_t size = eltsize * nmemb;
> struct rpc_state *rpc = buffer_;
> + update_pktline_state(rpc, ptr, size);
> write_or_die(rpc->in, ptr, size);
> return size;
> }
> @@ -659,6 +737,8 @@ static int post_rpc(struct rpc_state *rpc)
> curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, rpc_in);
> curl_easy_setopt(slot->curl, CURLOPT_FILE, rpc);
>
> + rpc->pktline_state = RPC_PKTLINE_INITIAL;
> +
> err = run_slot(slot, NULL);
> if (err == HTTP_REAUTH && !large_request) {
> credential_fill(&http_auth);
> @@ -667,6 +747,11 @@ static int post_rpc(struct rpc_state *rpc)
> if (err != HTTP_OK)
> err = -1;
>
> + if (rpc->pktline_state != RPC_PKTLINE_FLUSH) {
> + error("invalid or truncated response from http server");
> + err = -1;
> + }
> +
> curl_slist_free_all(headers);
> free(gzip_body);
> return err;