netman_watch_dns.c - openbmc/phosphor-networkd - Gitiles

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/inotify.h>
 #include <limits.h>
 #include <errno.h>
 #include <unistd.h>
 #include <systemd/sd-bus.h>

 /* Dbus settings to get the DNS entries updated in resolv.conf */
 const char *bus_name = "org.openbmc.NetworkManager";
 const char *object_path = "/org/openbmc/NetworkManager/Interface";
 const char *intf_name = "org.openbmc.NetworkManager";

 /* Used to tell Network Manager that Name Server listing is coming from DHCP */
 const char *DHCP_MARKER = "DHCP_AUTO= ";

 #define DHCP_MARKER_LEN strlen(DHCP_MARKER)

 /*
  * ----------------------------------------------
  *  Receives the buffer that has the IPs of DNS
  *  and then makes a dbus call to have these DNS
  *  entries updated in /etc/resolv.conf
  *  --------------------------------------------
  */
 int update_resolv_conf(const char *dns_entry)
 {
     /* To read the message sent by dbus handler */
     const char *resp_msg = NULL;

     /* Generic error handler */
     int rc = 0;

     if(dns_entry == NULL || !(strlen(dns_entry)))
     {
         fprintf(stderr,"Invalid DNS entry\n");
         return -1;
     }

     /*
      * Since 'state' file gets touched many a times during the network setting,
      * it does not make sense to  have the same DNS entry updated in
      * resolv.conf. SO we can actually have a cache of what was previously
      * updated and not update if the same DNS info is supplied again.
      * Eventhough this approach is a gain performance wise, it will
      * open up windows. Assume a case where DHCP has given 1.2.3.4 as IP and
      * user goes and updates the DNS as 4.5.6.7 and then user restarts the
      * network and thus getting the value of 1.2.3.4. If we maintain a cache of
      * what was previously updated, since we get 1.2.3.4 again, we will not
      * update with 1.2.3.4 eventhough that is needed since 4.5.6.7 would not
      * make sense. So doing updates to resolv.conf each time is bit of a
      * overkill but its error proof.
      */

     /* Encapsulated respose by dbus handler */
     sd_bus_message *response = NULL;

     /* Errors reported by dbus handler */
     sd_bus_error bus_error = SD_BUS_ERROR_NULL;

     /*
      * Gets a hook onto SYSTEM bus. This API may get called multiple
      * times so do not want to have so many instances of bus as it
      * leads to system resource issues. Re use the one that is present.
      */
     static sd_bus *bus_type = NULL;
     if(bus_type == NULL)
     {
         rc = sd_bus_open_system(&bus_type);
         if(rc < 0)
         {
             fprintf(stderr,"Error:[%s] getting system bus\n",strerror(-rc));
             return rc;
         }
     }

     rc = sd_bus_call_method(
                             bus_type,        /* In the System Bus */
                             bus_name,        /* Service to contact */
                             object_path,     /* Object path */
                             intf_name,       /* Interface name */
                             "SetNameServers",/* Method to be called */
                             &bus_error,      /* object to return error */
                             &response,       /* Response buffer if any */
                             "s",             /* Input as strings */
                             dns_entry,       /* string of DNS IPs */
                             NULL);           /* No return message expected */
     if(rc < 0)
     {
         fprintf(stderr,"ERROR updating DNS entries:[%s]\n",bus_error.message);
         goto finish;
     }

     /* Extract the encapsulated response message */
     rc = sd_bus_message_read(response, "s", &resp_msg);
     if (rc < 0)
     {
         fprintf(stderr,"Error:[%s] reading dns"
                 " updation status\n",strerror(-rc));
     }
     else
     {
         printf("%s\n",resp_msg);
     }

 finish:
     sd_bus_error_free(&bus_error);
     response = sd_bus_message_unref(response);

     return rc;
 }

 /*
  * ----------------------------------------------
  *  Gets invoked by inotify handler whenever the
  *  netif/state file gets modified
  *  -or- when this binary first gets launched.
  *  --------------------------------------------
  */
 int read_netif_state_file(const char *netif_dir, const char *state_file)
 {
     FILE *fp;

     /* Each line read from 'state' file */
     char *line = NULL;

     /* A list containing all the DNS IPs that are mentioned in 'state' file. */
     char *dns_list = NULL;

     /* length of each line read from 'state' file */
     size_t len = 0;

     /* Length of current and updated dns list */
     size_t list_len = 0;
     size_t new_list_len = 0;

     /* Generic error reporter */
     int rc = 0;

     /* Extract the 'state' file */
     char netif_state_file[strlen(netif_dir) + strlen(state_file) + 2];
     sprintf(netif_state_file,"%s%s", netif_dir,state_file);

     fp = fopen(netif_state_file,"r");
     if(fp == NULL)
     {
         fprintf(stderr,"Error opening[%s]\n",netif_state_file);
         return -1;
     }

     /*
      * Read the file line by line and look for the one that starts with DNS
      * If there is one, then what appears after DNS= are the IPs of the DNS
      * Just checking for DNS here since any non standard IP is rejected by
      * the dbus handler. This is to cater to cases where file may have DNS =
      */
     while ((getline(&line, &len, fp)) != -1)
     {
         if(!(strncmp(line,"DNS",3)))
         {
             /* Go all the way until the start of IPs */
             char *dns_entry = strrchr(line, '=');

             /* Advance to the first character after = */
             dns_entry = &((char *)dns_entry)[1];

             /* If we have never populated anything into the list */
             if(dns_list == NULL)
             {
                 /* The extra 2 characters to leave some gaps between DNS
                  * entries that would come from multiple lines since each line
                  * would start with DNS= and this overlaps with previous DNS IP.
                  * Although I don't see this as any reality to have DNS IPs
                  * spreading multiple lines.
                  */
                 list_len = strlen(dns_entry) + DHCP_MARKER_LEN + 2;
                 dns_list = (char *)malloc(list_len);

                 /*
                  * Populate DHCP_AUTO= along with the first line of DNS entries
                  * This will help in putting the appropriate comments in
                  * /etc/resolv.conf indicating the mode of DNS setting.
                  */
                 memset(dns_list, ' ', list_len);
                 memcpy(dns_list, DHCP_MARKER, DHCP_MARKER_LEN);
                 memcpy(&dns_list[DHCP_MARKER_LEN], dns_entry, strlen(dns_entry));
                 dns_list[list_len]='\0';
             }
             else
             {
                 /* This would be the entries that are coming from second+ line */
                 new_list_len = strlen(dns_entry) + list_len + 2;
                 dns_list = (char *)realloc(dns_list, new_list_len);

                 memset(&dns_list[list_len], ' ', strlen(dns_entry) + 2);
                 memmove(&dns_list[list_len], dns_entry, strlen(dns_entry));

                 /* Starting offset for next line */
                 list_len = new_list_len;
                 dns_list[list_len] = '\0';
             }
         }

         /* Memory is allocated by getline and user needs to free */
         if(line)
         {
             free(line);
             line = NULL;
         }
     }

     /* If we have found some or more DNS entries */
     if(dns_list)
     {
         /*
          * Being extra cautious if string somehow is not null terminated in the loop
          */
         dns_list[list_len] = '\0';

         rc = update_resolv_conf(dns_list);
         if(rc < 0)
         {
             fprintf(stderr,"Error updating resolv.conf with:[%s]\n",dns_list);
         }

         free(dns_list);
         dns_list = NULL;
     }

     return 0;
 }

 void usage(void)
 {
     printf("Usage: netman_watch_dns <Absolute path of DHCP netif state file>\n"
             "Example: netman_watch_dns /run/systemd/netif/state\n");
     return;
 }

 /*
  * ------------------------------------------------------
  *  Registers a inotify watch on the state file and calls
  *  into handling the state file whenever there is a change.
  * ------------------------------------------------------
  */
 int watch_for_dns_change(char *netif_dir, char *state_file)
 {
     int inotify_fd, wd;

     /* the aligned statement below is per the recommendation by inotify(7) */
     char event_data[4096]
         __attribute__ ((aligned(__alignof__(struct inotify_event))));

     /* To check the number of bytes read from inotify event */
     ssize_t bytes_read = 0;

     /* To walk event by event when inotify returns */
     char *ptr = NULL;

     /* Variable to hold individual event notification */
     const struct inotify_event *event = NULL;

     /* Generic error handler */
     int rc = 0;

     /* Create inotify instance */
     inotify_fd = inotify_init();
     if(inotify_fd == -1)
     {
         fprintf(stderr,"Error:[%s] initializing Inotify",strerror(errno));
         return -1;
     }

     /* Register to write actions on the netif directory */
     wd = inotify_add_watch(inotify_fd, netif_dir, IN_MODIFY);
     if(wd == -1)
     {
         fprintf(stderr,"Error:[%s] adding watch for:[%s]\n",
                 strerror(errno), netif_dir);
         return -1;
     }

     /*
      * When this is first launched, we need to go see
      * if there is anything present in the state file.
      * Doing it here to close any gaps between the file
      * getting created before registering inotifier.
      */
     rc = read_netif_state_file(netif_dir, state_file);
     if(rc < 0)
     {
         fprintf(stderr,"Error doing initial processing of state file\n");
     }

     /* Read events forever */
     for (;;)
     {
         memset(event_data, 0x0, sizeof(event_data));
         bytes_read = read(inotify_fd, event_data, sizeof(event_data));
         if(bytes_read <= 0)
         {
             fprintf(stderr,"event_data read from inotify fd was Invalid\n");
             continue;
         }

         /* Process all of the events in buffer returned by read() */
         for(ptr = event_data; ptr < event_data + bytes_read;
             ptr += sizeof(struct inotify_event) + event->len)
         {
             event = (struct inotify_event *)ptr;

             /*
              * We are not interested in anything other than updates to
              * state file. Now when this code is being written, its in
              * /run/systemd/netif/state.
              */
             if((event->len > 0) && (strstr(event->name, state_file)))
             {
                 rc = read_netif_state_file(netif_dir, state_file);
                 if(rc < 0)
                 {
                     fprintf(stderr,"Error processing inotify event\n");
                 }
             }
         } /* Processing all inotify events. */
     } /* Endless loop waiting for events. */

     /*
      * Technically, we should not reach here since the monitor function
      * is not supposed to stop even on error. But for completeness.....
      */
     inotify_rm_watch(inotify_fd, wd);
     close(inotify_fd);

     return 0;
 }

 int main(int argc, char *argv[])
 {
     /* Generic error handler */
     int rc = 0;

     /* Sanity checking */
     if(argc != 2 || argv[1] == NULL)
     {
         usage();
         return -1;
     }

     /*
      * We now have the job of extracting the directory and
      * the state file from the user supplied input.
      */
     char netif_dir[strlen(argv[1]) + 1];
     memset(netif_dir, 0x0, sizeof(netif_dir));

     /* File where the actual DNS= entry is found */
     char *state_file = NULL;

     /* Filter invalid inputs */
     state_file = strrchr(argv[1], '/');
     if(strlen(state_file) <= 1)
     {
         fprintf(stderr,"Invalid state file :[%s] specified\n",state_file);
         return -1;
     }
     else
     {
         /* we have /state now and what we need is just the 'state' */
         state_file = &((char *)state_file)[1];

         /*
          * Also extract the Absolute Path of the directory
          * containing this state file
          */
         strncpy(netif_dir, argv[1], strlen(argv[1]) - strlen(state_file));
         strcat(netif_dir,"\0");
     }

     printf("Watching for changes in DNS settings..\n");

      /* Commenting since this functionality has been built into network
       * manager and this file will be deleted in the very next commit
       */
     /*
     rc = watch_for_dns_change(netif_dir, state_file);
     if(rc < 0)
     {
         fprintf(stderr,"Error watching for DNS changes\n");
     }
     */

     // Returning will result in app getting launched again per Restart
     // policy in service file
     pause();

     return rc;
 }
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/inotify.h>
	#include <limits.h>
	#include <errno.h>
	#include <unistd.h>
	#include <systemd/sd-bus.h>

	/* Dbus settings to get the DNS entries updated in resolv.conf */
	const char *bus_name = "org.openbmc.NetworkManager";
	const char *object_path = "/org/openbmc/NetworkManager/Interface";
	const char *intf_name = "org.openbmc.NetworkManager";

	/* Used to tell Network Manager that Name Server listing is coming from DHCP */
	const char *DHCP_MARKER = "DHCP_AUTO= ";

	#define DHCP_MARKER_LEN strlen(DHCP_MARKER)

	/*
	* ----------------------------------------------
	* Receives the buffer that has the IPs of DNS
	* and then makes a dbus call to have these DNS
	* entries updated in /etc/resolv.conf
	* --------------------------------------------
	*/
	int update_resolv_conf(const char *dns_entry)
	{
	/* To read the message sent by dbus handler */
	const char *resp_msg = NULL;

	/* Generic error handler */
	int rc = 0;

	if(dns_entry == NULL \|\| !(strlen(dns_entry)))
	{
	fprintf(stderr,"Invalid DNS entry\n");
	return -1;
	}

	/*
	* Since 'state' file gets touched many a times during the network setting,
	* it does not make sense to have the same DNS entry updated in
	* resolv.conf. SO we can actually have a cache of what was previously
	* updated and not update if the same DNS info is supplied again.
	* Eventhough this approach is a gain performance wise, it will
	* open up windows. Assume a case where DHCP has given 1.2.3.4 as IP and
	* user goes and updates the DNS as 4.5.6.7 and then user restarts the
	* network and thus getting the value of 1.2.3.4. If we maintain a cache of
	* what was previously updated, since we get 1.2.3.4 again, we will not
	* update with 1.2.3.4 eventhough that is needed since 4.5.6.7 would not
	* make sense. So doing updates to resolv.conf each time is bit of a
	* overkill but its error proof.
	*/

	/* Encapsulated respose by dbus handler */
	sd_bus_message *response = NULL;

	/* Errors reported by dbus handler */
	sd_bus_error bus_error = SD_BUS_ERROR_NULL;

	/*
	* Gets a hook onto SYSTEM bus. This API may get called multiple
	* times so do not want to have so many instances of bus as it
	* leads to system resource issues. Re use the one that is present.
	*/
	static sd_bus *bus_type = NULL;
	if(bus_type == NULL)
	{
	rc = sd_bus_open_system(&bus_type);
	if(rc < 0)
	{
	fprintf(stderr,"Error:[%s] getting system bus\n",strerror(-rc));
	return rc;
	}
	}

	rc = sd_bus_call_method(
	bus_type, /* In the System Bus */
	bus_name, /* Service to contact */
	object_path, /* Object path */
	intf_name, /* Interface name */
	"SetNameServers",/* Method to be called */
	&bus_error, /* object to return error */
	&response, /* Response buffer if any */
	"s", /* Input as strings */
	dns_entry, /* string of DNS IPs */
	NULL); /* No return message expected */
	if(rc < 0)
	{
	fprintf(stderr,"ERROR updating DNS entries:[%s]\n",bus_error.message);
	goto finish;
	}

	/* Extract the encapsulated response message */
	rc = sd_bus_message_read(response, "s", &resp_msg);
	if (rc < 0)
	{
	fprintf(stderr,"Error:[%s] reading dns"
	" updation status\n",strerror(-rc));
	}
	else
	{
	printf("%s\n",resp_msg);
	}

	finish:
	sd_bus_error_free(&bus_error);
	response = sd_bus_message_unref(response);

	return rc;
	}

	/*
	* ----------------------------------------------
	* Gets invoked by inotify handler whenever the
	* netif/state file gets modified
	* -or- when this binary first gets launched.
	* --------------------------------------------
	*/
	int read_netif_state_file(const char netif_dir, const char state_file)
	{
	FILE *fp;

	/* Each line read from 'state' file */
	char *line = NULL;

	/* A list containing all the DNS IPs that are mentioned in 'state' file. */
	char *dns_list = NULL;

	/* length of each line read from 'state' file */
	size_t len = 0;

	/* Length of current and updated dns list */
	size_t list_len = 0;
	size_t new_list_len = 0;

	/* Generic error reporter */
	int rc = 0;

	/* Extract the 'state' file */
	char netif_state_file[strlen(netif_dir) + strlen(state_file) + 2];
	sprintf(netif_state_file,"%s%s", netif_dir,state_file);

	fp = fopen(netif_state_file,"r");
	if(fp == NULL)
	{
	fprintf(stderr,"Error opening[%s]\n",netif_state_file);
	return -1;
	}

	/*
	* Read the file line by line and look for the one that starts with DNS
	* If there is one, then what appears after DNS= are the IPs of the DNS
	* Just checking for DNS here since any non standard IP is rejected by
	* the dbus handler. This is to cater to cases where file may have DNS =
	*/
	while ((getline(&line, &len, fp)) != -1)
	{
	if(!(strncmp(line,"DNS",3)))
	{
	/* Go all the way until the start of IPs */
	char *dns_entry = strrchr(line, '=');

	/* Advance to the first character after = */
	dns_entry = &((char *)dns_entry)[1];

	/* If we have never populated anything into the list */
	if(dns_list == NULL)
	{
	/* The extra 2 characters to leave some gaps between DNS
	* entries that would come from multiple lines since each line
	* would start with DNS= and this overlaps with previous DNS IP.
	* Although I don't see this as any reality to have DNS IPs
	* spreading multiple lines.
	*/
	list_len = strlen(dns_entry) + DHCP_MARKER_LEN + 2;
	dns_list = (char *)malloc(list_len);

	/*
	* Populate DHCP_AUTO= along with the first line of DNS entries
	* This will help in putting the appropriate comments in
	* /etc/resolv.conf indicating the mode of DNS setting.
	*/
	memset(dns_list, ' ', list_len);
	memcpy(dns_list, DHCP_MARKER, DHCP_MARKER_LEN);
	memcpy(&dns_list[DHCP_MARKER_LEN], dns_entry, strlen(dns_entry));
	dns_list[list_len]='\0';
	}
	else
	{
	/* This would be the entries that are coming from second+ line */
	new_list_len = strlen(dns_entry) + list_len + 2;
	dns_list = (char *)realloc(dns_list, new_list_len);

	memset(&dns_list[list_len], ' ', strlen(dns_entry) + 2);
	memmove(&dns_list[list_len], dns_entry, strlen(dns_entry));

	/* Starting offset for next line */
	list_len = new_list_len;
	dns_list[list_len] = '\0';
	}
	}

	/* Memory is allocated by getline and user needs to free */
	if(line)
	{
	free(line);
	line = NULL;
	}
	}

	/* If we have found some or more DNS entries */
	if(dns_list)
	{
	/*
	* Being extra cautious if string somehow is not null terminated in the loop
	*/
	dns_list[list_len] = '\0';

	rc = update_resolv_conf(dns_list);
	if(rc < 0)
	{
	fprintf(stderr,"Error updating resolv.conf with:[%s]\n",dns_list);
	}

	free(dns_list);
	dns_list = NULL;
	}

	return 0;
	}

	void usage(void)
	{
	printf("Usage: netman_watch_dns <Absolute path of DHCP netif state file>\n"
	"Example: netman_watch_dns /run/systemd/netif/state\n");
	return;
	}

	/*
	* ------------------------------------------------------
	* Registers a inotify watch on the state file and calls
	* into handling the state file whenever there is a change.
	* ------------------------------------------------------
	*/
	int watch_for_dns_change(char netif_dir, char state_file)
	{
	int inotify_fd, wd;

	/* the aligned statement below is per the recommendation by inotify(7) */
	char event_data[4096]
	__attribute__ ((aligned(__alignof__(struct inotify_event))));

	/* To check the number of bytes read from inotify event */
	ssize_t bytes_read = 0;

	/* To walk event by event when inotify returns */
	char *ptr = NULL;

	/* Variable to hold individual event notification */
	const struct inotify_event *event = NULL;

	/* Generic error handler */
	int rc = 0;

	/* Create inotify instance */
	inotify_fd = inotify_init();
	if(inotify_fd == -1)
	{
	fprintf(stderr,"Error:[%s] initializing Inotify",strerror(errno));
	return -1;
	}

	/* Register to write actions on the netif directory */
	wd = inotify_add_watch(inotify_fd, netif_dir, IN_MODIFY);
	if(wd == -1)
	{
	fprintf(stderr,"Error:[%s] adding watch for:[%s]\n",
	strerror(errno), netif_dir);
	return -1;
	}

	/*
	* When this is first launched, we need to go see
	* if there is anything present in the state file.
	* Doing it here to close any gaps between the file
	* getting created before registering inotifier.
	*/
	rc = read_netif_state_file(netif_dir, state_file);
	if(rc < 0)
	{
	fprintf(stderr,"Error doing initial processing of state file\n");
	}

	/* Read events forever */
	for (;;)
	{
	memset(event_data, 0x0, sizeof(event_data));
	bytes_read = read(inotify_fd, event_data, sizeof(event_data));
	if(bytes_read <= 0)
	{
	fprintf(stderr,"event_data read from inotify fd was Invalid\n");
	continue;
	}

	/* Process all of the events in buffer returned by read() */
	for(ptr = event_data; ptr < event_data + bytes_read;
	ptr += sizeof(struct inotify_event) + event->len)
	{
	event = (struct inotify_event *)ptr;

	/*
	* We are not interested in anything other than updates to
	* state file. Now when this code is being written, its in
	* /run/systemd/netif/state.
	*/
	if((event->len > 0) && (strstr(event->name, state_file)))
	{
	rc = read_netif_state_file(netif_dir, state_file);
	if(rc < 0)
	{
	fprintf(stderr,"Error processing inotify event\n");
	}
	}
	} /* Processing all inotify events. */
	} /* Endless loop waiting for events. */

	/*
	* Technically, we should not reach here since the monitor function
	* is not supposed to stop even on error. But for completeness.....
	*/
	inotify_rm_watch(inotify_fd, wd);
	close(inotify_fd);

	return 0;
	}

	int main(int argc, char *argv[])
	{
	/* Generic error handler */
	int rc = 0;

	/* Sanity checking */
	if(argc != 2 \|\| argv[1] == NULL)
	{
	usage();
	return -1;
	}

	/*
	* We now have the job of extracting the directory and
	* the state file from the user supplied input.
	*/
	char netif_dir[strlen(argv[1]) + 1];
	memset(netif_dir, 0x0, sizeof(netif_dir));

	/* File where the actual DNS= entry is found */
	char *state_file = NULL;

	/* Filter invalid inputs */
	state_file = strrchr(argv[1], '/');
	if(strlen(state_file) <= 1)
	{
	fprintf(stderr,"Invalid state file :[%s] specified\n",state_file);
	return -1;
	}
	else
	{
	/* we have /state now and what we need is just the 'state' */
	state_file = &((char *)state_file)[1];

	/*
	* Also extract the Absolute Path of the directory
	* containing this state file
	*/
	strncpy(netif_dir, argv[1], strlen(argv[1]) - strlen(state_file));
	strcat(netif_dir,"\0");
	}

	printf("Watching for changes in DNS settings..\n");

	/* Commenting since this functionality has been built into network
	* manager and this file will be deleted in the very next commit
	*/
	/*
	rc = watch_for_dns_change(netif_dir, state_file);
	if(rc < 0)
	{
	fprintf(stderr,"Error watching for DNS changes\n");
	}
	*/

	// Returning will result in app getting launched again per Restart
	// policy in service file
	pause();

	return rc;
	}