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gluon-neighbour-info: fix broken output with large results (#2322)

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Currently a buffer with a fixed size of 8192 bytes is used. However the
result can potentially be larger, which leads to a truncated JSON
output on stdout. UDP packets, without compression and with IP
fragmentation, can be up to 64KiB large.

Instead of using a fixed size buffer on the stack ask the kernel first
about the size of the UDP data and allocate a buffer of appropriate size
on the heap before receiving the UDP data.

The issue was observed with a custom respondd provider.

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
This commit is contained in:
T-X 2021-10-04 21:23:29 +02:00 committed by GitHub
parent c5f5fc5624
commit 531937cf6f
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 36 additions and 7 deletions
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43
package/gluon-neighbour-info/src/gluon-neighbour-info.c
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@ -69,8 +69,23 @@ void tv_subtract (struct timeval *r, const struct timeval *a, const struct timev
}
}
ssize_t recvtimeout(int socket, void *buffer, size_t length, int flags, const struct timeval *timeout) {
void resize_recvbuffer(char **recvbuffer, size_t *recvbuffer_len, size_t recvlen)
{
free(*recvbuffer);
*recvbuffer = malloc(recvlen);
if (!(*recvbuffer)) {
perror("Could not resize recvbuffer");
exit(EXIT_FAILURE);
}
*recvbuffer_len = recvlen;
}
ssize_t recvtimeout(int socket, char **recvbuffer, size_t *recvbuffer_len,
const struct timeval *timeout) {
struct timeval now, timeout_left;
ssize_t recvlen;
getclock(&now);
tv_subtract(&timeout_left, timeout, &now);
@ -79,18 +94,28 @@ ssize_t recvtimeout(int socket, void *buffer, size_t length, int flags, const st
return -1;
setsockopt(socket, SOL_SOCKET, SO_RCVTIMEO, &timeout_left, sizeof(timeout_left));
return recv(socket, buffer, length, flags);
recvlen = recv(socket, NULL, 0, MSG_PEEK | MSG_TRUNC);
if (recvlen < 0)
return recvlen;
if (recvlen > *recvbuffer_len)
resize_recvbuffer(recvbuffer, recvbuffer_len, recvlen);
return recv(socket, *recvbuffer, *recvbuffer_len, 0);
}
int request(const int sock, const struct sockaddr_in6 *client_addr, const char *request, const char *sse, double timeout, unsigned int max_count) {
int request(const int sock, char **recvbuffer, size_t *recvbuffer_len,
const struct sockaddr_in6 *client_addr, const char *request,
const char *sse, double timeout, unsigned int max_count) {
ssize_t ret;
char buffer[8192];
unsigned int count = 0;
ret = sendto(sock, request, strlen(request), 0, (struct sockaddr *)client_addr, sizeof(struct sockaddr_in6));
if (ret < 0) {
perror("Error in sendto()");
free(*recvbuffer);
exit(EXIT_FAILURE);
}
@ -105,7 +130,7 @@ int request(const int sock, const struct sockaddr_in6 *client_addr, const char *
}
do {
ret = recvtimeout(sock, buffer, sizeof(buffer), 0, &tv_timeout);
ret = recvtimeout(sock, recvbuffer, recvbuffer_len, &tv_timeout);
if (ret < 0)
break;
@ -116,7 +141,7 @@ int request(const int sock, const struct sockaddr_in6 *client_addr, const char *
fputs("data: ", stdout);
}
fwrite(buffer, sizeof(char), ret, stdout);
fwrite(*recvbuffer, sizeof(char), ret, stdout);
if (sse)
fputs("\n\n", stdout);
@ -137,6 +162,8 @@ int main(int argc, char **argv) {
int sock;
struct sockaddr_in6 client_addr = {};
char *request_string = NULL;
char *recvbuffer = NULL;
size_t recvbuffer_len = 0;
sock = socket(PF_INET6, SOCK_DGRAM, 0);
@ -243,11 +270,13 @@ int main(int argc, char **argv) {
}
do {
ret = request(sock, &client_addr, request_string, sse, timeout, max_count);
ret = request(sock, &recvbuffer, &recvbuffer_len, &client_addr,
request_string, sse, timeout, max_count);
} while(loop);
if (sse)
fputs("event: eot\ndata: null\n\n", stdout);
free(recvbuffer);
return ret;
}