Publish urlmount.c as 'misc'

It hasn't been packaged yet, but make it public while getting
ready to package.

misc/urlmount.c

@@ -0,0 +1,232 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2021 Lenovo
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#define FUSE_USE_VERSION 26
+#include <fuse.h>
+#include <curl/curl.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <unistd.h>
+
+CURL *curl;
+
+char curlerror[CURL_ERROR_SIZE];
+curl_off_t filesize;
+
+typedef struct downloadbuffer {
+    char *response;
+    size_t completed;
+    size_t total;
+} downloadbuffer;
+
+#define MAX_FILE_LEN 1024
+#define MAX_URL_PATHS 512
+static char filename[MAX_FILE_LEN];
+static int urlidx;
+static char* urls[MAX_URL_PATHS];
+
+
+static int http_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
+                        off_t offset, struct fuse_file_info *fi)
+{
+    if (strcmp(path, "/") != 0)  // We don't support subdirs
+        return -ENOENT;
+    filler(buf, ".", NULL, 0);
+    filler(buf, "..", NULL, 0);
+    filler(buf, filename + 1, NULL, 0);
+    return 0;
+}
+
+size_t fill_buffer(char *data, size_t size, size_t nmemb, downloadbuffer *userdata) {
+    size_t amount;
+    amount = size * nmemb;
+    if (userdata->total < amount + userdata->completed) return 0;
+    memcpy(&(userdata->response[userdata->completed]), data, amount);
+    userdata->completed += amount;
+    return amount;
+}
+
+static int http_read(const char *path, char *buf, size_t size, off_t offset,
+                     struct fuse_file_info *fi) {
+    char headbuffer[512];
+    double dldbl = 0.0;
+    int startidx;
+    int reconnecting = 0;
+    FILE* fd;
+    startidx = urlidx;
+    memset(buf, 0, size);
+    curl_off_t downloaded;
+    //Would be needed for multithread, however preferring to conserve
+    //filehandles rather than go multithread
+    // Some comparisons showed that the threaded performance boost doesn't
+    // do even offset the overhead of the new curl handles, so better
+    // to use single threaded curl overall for now
+    //CURL *tmpcurl = curl_easy_duphandle(curl);
+    downloadbuffer dlbuf;
+    dlbuf.response = buf;
+    dlbuf.completed = 0;
+    dlbuf.total = size;
+    fd = NULL;
+
+    if (strcmp(path, filename) != 0) return -ENOENT;
+    memset(headbuffer, 0, 512);
+    snprintf(headbuffer, 512, "%ld-%ld", offset, offset + size - 1);
+    curl_easy_setopt(curl, CURLOPT_RANGE, headbuffer);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &dlbuf);
+    while (curl_easy_perform(curl) != CURLE_OK) {
+        reconnecting = 1;
+        fd = fopen("/dev/kmsg", "w+");
+        dlbuf.completed = 0;
+        fprintf(fd, "<1>urlmount: error while communicating with %s: %s\n", urls[urlidx], curlerror);
+        urlidx++;
+        if (urls[urlidx] == NULL)
+            urlidx = 0;
+        if (urlidx == startidx)
+            sleep(10);
+        fprintf(fd, "urlmount: Connecting to %s\n", urls[urlidx]);
+        curl_easy_setopt(curl, CURLOPT_URL, urls[urlidx]);
+        fclose(fd);
+    }
+    if (reconnecting) {
+        fd = fopen("/dev/kmsg", "w+");
+        fprintf(fd, "<1>urlmount: Successfully connected to %s\n", urls[urlidx]);
+        fclose(fd);
+    }
+    curl_easy_getinfo(curl, CURLINFO_SIZE_DOWNLOAD, &dldbl);
+    downloaded = round(dldbl);
+    //Would be needed for multithread
+    //curl_easy_cleanup(tmpcurl);
+    return downloaded;
+}
+
+static int http_open(const char *path, struct fuse_file_info *fi) {
+    if (strcmp(path, filename) != 0)
+        return -ENOENT;
+
+    if ((fi->flags & 3) != O_RDONLY)
+        return -EACCES;
+
+    return 0;
+}
+
+static void* http_init(struct fuse_conn_info *conn) {
+    // Because we fork, we need to redo curl
+    // or else suffer the wrath of NSS TLS
+    curl_global_init(CURL_GLOBAL_DEFAULT);
+    curl = curl_easy_init();
+    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curlerror);
+    //We want to consider error conditions fatal, rather than
+    //passing error text as data
+    curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
+    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 10L);
+    curl_easy_setopt(curl, CURLOPT_URL, urls[urlidx]);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fill_buffer);
+    return NULL;
+}
+
+static int http_getattr(const char *path, struct stat *st) {
+    memset(st, 0, sizeof(struct stat));
+
+    if (strcmp(path, "/") == 0) {
+        st->st_mode = S_IFDIR | 0555;
+        st->st_nlink = 2;
+    } else if (strcmp(path, filename) == 0) {
+        st->st_mode = S_IFREG | 0444;
+        st->st_nlink = 1;
+        st->st_size = filesize; // TODO: fix with curl HEAD
+    } else
+        return -ENOENT;
+    return 0;
+}
+
+
+static const struct fuse_operations http_ops = {
+    .getattr = http_getattr,
+    .readdir = http_readdir,
+    .read = http_read,
+    .open = http_open,
+    .init = http_init,
+};
+
+int main(int argc, char* argv[]) {
+    char *tmp;
+    double fsize;
+    int i, j;
+    srand(time(NULL));
+    j = 0;
+    memset(urls, 0, 32*sizeof(char*));
+    urlidx = 0;
+    curl_global_init(CURL_GLOBAL_DEFAULT);
+    curl = curl_easy_init();
+    curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curlerror);
+    //We want to consider error conditions fatal, rather than
+    //passing error text as data
+    curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
+    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 15L);
+    memset(filename, 0, MAX_FILE_LEN);
+    for (i=0; i < argc; i++) {
+        if (strstr(argv[i], ":") > 0) {
+            if (j <= MAX_URL_PATHS) {
+                urls[j] = argv[i];
+                tmp = strrchr(urls[j++], '/');
+                strncpy(filename, tmp, MAX_FILE_LEN);
+            }
+            //Request single threaded mode, as curl would need more
+            // filehandles for multithread
+            argv[i] = "-s";
+        }
+    }
+    if (filename[0] == 0) {
+        fprintf(stderr, "No URL given in arguments\n");
+        exit(1);
+    }
+    for (i=0; urls[i] != NULL; i++) {
+        printf("Registering mount path: %s\n", urls[i]);
+    }
+    urlidx = rand() % j;
+    j = urlidx;
+    printf("Connecting to %s\n", urls[urlidx]);
+    curl_easy_setopt(curl, CURLOPT_URL, urls[urlidx]);
+    curl_easy_setopt(curl, CURLOPT_NOBODY, 1);
+    while (curl_easy_perform(curl) != CURLE_OK) {
+        fprintf(stderr, "urlmount: error while communicating with %s: %s\n", urls[urlidx++], curlerror);
+        if (urls[urlidx] == NULL)
+            urlidx = 0;
+        if (urlidx == j) {
+            fprintf(stderr, "urlmount: Unable to reach any target url, aborting\n");
+            exit(1);
+        }
+        printf("Connecting to %s\n", urls[urlidx]);
+        curl_easy_setopt(curl, CURLOPT_URL, urls[urlidx]);
+    }
+    printf("Successfully connected to %s\n", urls[urlidx]);
+    curl_easy_getinfo(curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &fsize);
+    filesize = round(fsize);
+    curl_easy_setopt(curl, CURLOPT_NOBODY, 0);
+    if (filesize < 1) {
+        fprintf(stderr, "Unable to reach designated URL\n");
+        exit(1);
+    }
+    if (!curl) {
+        fprintf(stderr, "Unable to initialize CURL!\n");
+        exit(1);
+    }
+    curl_easy_cleanup(curl);
+    curl_global_cleanup();
+    fuse_main(argc, argv, &http_ops, NULL);
+}