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respondd: add support for delayed replies to multicast requests (#144)

This commit is contained in:
lemoer 2016-12-06 19:46:40 +01:00 committed by Matthias Schiffer
parent 738d8a2365
commit e7fbcf75a9
1 changed files with 271 additions and 31 deletions
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302
net/respondd/src/respondd.c
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@ -1,6 +1,7 @@
/*
Copyright (c) 2014-2015, Nils Schneider <nils@nilsschneider.net>
Copyright (c) 2015-2016, Matthias Schiffer <mschiffer@universe-factory.net>
Copyright (c) 2016 Leonardo Mörlein <me@irrelefant.net>
All rights reserved.
Redistribution and use in source and binary forms, with or without
@ -41,6 +42,7 @@
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#include <net/if.h>
@ -48,6 +50,16 @@
#include <sys/types.h>
#include <sys/socket.h>
#define SCHEDULE_LEN 8
#define REQUEST_MAXLEN 256
#define MAX_MULTICAST_DELAY_DEFAULT 0
struct interface_delay_info {
struct interface_delay_info *next;
unsigned int ifindex;
uint64_t max_multicast_delay;
};
struct provider_list {
struct provider_list *next;
@ -64,6 +76,18 @@ struct request_type {
int64_t cache_timeout;
};
struct request_task {
struct request_task *next;
int64_t scheduled_time;
struct sockaddr_in6 client_addr;
char request[REQUEST_MAXLEN];
};
struct request_schedule {
size_t length;
struct request_task *list_head;
};
static int64_t now;
static struct hsearch_data htab;
@ -79,15 +103,18 @@ static void usage() {
puts(" -p <int> port number to listen on");
puts(" -g <ip6> multicast group, e.g. ff02::2:1001");
puts(" -i <string> interface on which the group is joined");
puts(" -t <int> maximum delay seconds before multicast responses");
puts(" for the last specified multicast interface (default: 0)");
puts(" -d <string> data provider directory (default: current directory)");
puts(" -h this help\n");
}
static void join_mcast(const int sock, const struct in6_addr addr, const char *iface) {
// returns true on success
static bool join_mcast(const int sock, const struct in6_addr addr, unsigned int ifindex) {
struct ipv6_mreq mreq;
mreq.ipv6mr_multiaddr = addr;
mreq.ipv6mr_interface = if_nametoindex(iface);
mreq.ipv6mr_interface = ifindex;
if (mreq.ipv6mr_interface == 0)
goto error;
@ -95,11 +122,11 @@ static void join_mcast(const int sock, const struct in6_addr addr, const char *i
if (setsockopt(sock, IPPROTO_IPV6, IPV6_JOIN_GROUP, &mreq, sizeof(mreq)) == -1)
goto error;
return;
return true;
error:
fprintf(stderr, "Could not join multicast group on %s: ", iface);
perror(NULL);
return false;
}
@ -165,6 +192,55 @@ static const struct respondd_provider_info * get_providers(const char *filename)
return ret;
}
bool schedule_push_request(struct request_schedule *s, struct request_task *new_task) {
if (s->length >= SCHEDULE_LEN)
// schedule is full
return false;
// insert into sorted list
struct request_task **pos;
for (pos = &s->list_head; *pos; pos = &((*pos)->next)) {
if ((*pos)->scheduled_time > new_task->scheduled_time)
break;
}
// insert before *pos
new_task->next = *pos;
*pos = new_task;
s->length++;
return true;
}
int64_t schedule_idle_time(struct request_schedule *s) {
if (!s->list_head)
// nothing to do yet (0 = infinite time)
return 0;
int64_t result = s->list_head->scheduled_time - now;
if (result <= 0)
return -1; // zero is infinity
else
return result;
}
struct request_task * schedule_pop_request(struct request_schedule *s) {
if (!s->list_head)
// schedule is empty
return NULL;
if (schedule_idle_time(s) >= 0) {
// nothing to do yet
return NULL;
}
struct request_task *result = s->list_head;
s->list_head = s->list_head->next;
s->length--;
return result;
}
static void load_cache_time(struct request_type *r, const char *name) {
r->cache = NULL;
r->cache_time = 0;
@ -308,8 +384,6 @@ static struct json_object * handle_request(char *request, bool *compress) {
if (!*request)
return NULL;
update_time();
if (!strncmp(request, "GET ", 4)) {
*compress = true;
return multi_request(request+4);
@ -320,27 +394,10 @@ static struct json_object * handle_request(char *request, bool *compress) {
}
}
static void serve(int sock) {
char input[256];
void send_response(int sock, struct json_object *result, bool compress,
struct sockaddr_in6 *addr) {
const char *output = NULL;
ssize_t input_bytes, output_bytes;
struct sockaddr_in6 addr;
socklen_t addrlen = sizeof(addr);
bool compress;
input_bytes = recvfrom(sock, input, sizeof(input)-1, 0, (struct sockaddr *)&addr, &addrlen);
if (input_bytes < 0) {
perror("recvfrom failed");
exit(EXIT_FAILURE);
}
input[input_bytes] = 0;
struct json_object *result = handle_request(input, &compress);
if (!result)
return;
size_t output_bytes;
const char *str = json_object_to_json_string_ext(result, JSON_C_TO_STRING_PLAIN);
@ -361,13 +418,143 @@ static void serve(int sock) {
}
if (output) {
if (sendto(sock, output, output_bytes, 0, (struct sockaddr *)&addr, addrlen) < 0)
if (sendto(sock, output, output_bytes, 0, (struct sockaddr *) addr, sizeof(*addr)) < 0)
perror("sendto failed");
}
json_object_put(result);
}
void serve_request(struct request_task *task, int sock) {
bool compress;
struct json_object *result = handle_request(task->request, &compress);
if (!result)
return;
send_response(
sock,
result,
compress,
&task->client_addr
);
}
/**
* Wait for an incoming request and schedule it.
*
* 1a. If the schedule is empty, we wait infinite time.
* 1b. If we have scheduled requests, we only wait for incoming requests
* until we reach the scheduling deadline.
* 1c. If there is no request incomming in the above time, the fuction will
* return.
* 2a. If the incoming request was sent to a multicast destination IPv6,
* check whether there was set a max multicast delay for the incomming iface
* in if_delay_info_list.
* 2b. If so choose a random delay between 0 and max_multicast_delay milliseconds
* and schedule the request.
* 2c. If not, send the request immediately.
* 2d. If the schedule is full, send the reply immediately.
* 3a. If the incoming request was sent to a unicast destination, the response
* will be also sent immediately.
*/
static void accept_request(struct request_schedule *schedule, int sock,
struct interface_delay_info *if_delay_info_list) {
char input[REQUEST_MAXLEN];
ssize_t input_bytes;
struct sockaddr_in6 addr;
char control[256];
struct in6_addr destaddr = {};
struct cmsghdr *cmsg;
unsigned int ifindex = 0;
int recv_errno;
int64_t timeout = schedule_idle_time(schedule);
if (timeout < 0)
return;
// set timeout to the socket
struct timeval t;
t.tv_sec = ((uint64_t) timeout) / 1000;
t.tv_usec = (((uint64_t) timeout) % 1000) * 1000;
if (setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &t, sizeof(t)) < 0)
perror("setsockopt failed\n");
struct iovec iv = {
.iov_base = input,
.iov_len = sizeof(input) - 1
};
struct msghdr mh = {
.msg_name = &addr,
.msg_namelen = sizeof(addr),
.msg_iov = &iv,
.msg_iovlen = 1,
.msg_control = control,
.msg_controllen = sizeof(control)
};
input_bytes = recvmsg(sock, &mh, 0);
recv_errno = errno;
update_time();
// Timeout
errno = recv_errno;
if (input_bytes < 0 && (errno == EAGAIN || errno == EWOULDBLOCK))
return;
if (input_bytes < 0) {
perror("recvmsg failed");
exit(EXIT_FAILURE);
}
// determine destination address
for (cmsg = CMSG_FIRSTHDR(&mh); cmsg != NULL; cmsg = CMSG_NXTHDR(&mh, cmsg))
{
// skip other packet headers
if (cmsg->cmsg_level != IPPROTO_IPV6 || cmsg->cmsg_type != IPV6_PKTINFO)
continue;
struct in6_pktinfo *pi = (struct in6_pktinfo *) CMSG_DATA(cmsg);
destaddr = pi->ipi6_addr;
ifindex = pi->ipi6_ifindex;
break;
}
input[input_bytes] = 0;
// get the max delay
uint64_t max_multicast_delay = MAX_MULTICAST_DELAY_DEFAULT;
struct interface_delay_info *tmp = if_delay_info_list;
for (; tmp; tmp = tmp->next) {
if (tmp->ifindex == ifindex) {
max_multicast_delay = tmp->max_multicast_delay;
break;
}
}
struct request_task *new_task = malloc(sizeof(*new_task));
// the ternary operator avoids division by 0
new_task->scheduled_time = max_multicast_delay ? now + rand() % max_multicast_delay : 0;
strncpy(new_task->request, input, input_bytes + 1);
new_task->request[input_bytes] = 0;
new_task->client_addr = addr;
bool is_scheduled;
if(new_task->scheduled_time && IN6_IS_ADDR_MULTICAST(&destaddr))
// scheduling could fail because the schedule is full
is_scheduled = schedule_push_request(schedule, new_task);
else
// unicast packets are always sent directly
is_scheduled = false;
if (!is_scheduled) {
// reply immediately
serve_request(new_task, sock);
free(new_task);
}
}
int main(int argc, char **argv) {
const int one = 1;
@ -376,6 +563,8 @@ int main(int argc, char **argv) {
struct sockaddr_in6 server_addr = {};
struct in6_addr mgroup_addr;
srand(time(NULL));
sock = socket(PF_INET6, SOCK_DGRAM, 0);
if (sock < 0) {
@ -388,15 +577,24 @@ int main(int argc, char **argv) {
exit(EXIT_FAILURE);
}
if (setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one))) {
perror("can't set socket to deliver IPV6_PKTINFO control message");
exit(EXIT_FAILURE);
}
server_addr.sin6_family = AF_INET6;
server_addr.sin6_addr = in6addr_any;
char *endptr;
opterr = 0;
int group_set = 0;
bool iface_set = false;
unsigned int last_ifindex = 0;
struct interface_delay_info *if_delay_info_list = NULL;
int c;
while ((c = getopt(argc, argv, "p:g:i:d:h")) != -1) {
while ((c = getopt(argc, argv, "p:g:t:i:d:h")) != -1) {
switch (c) {
case 'p':
server_addr.sin6_port = htons(atoi(optarg));
@ -416,7 +614,38 @@ int main(int argc, char **argv) {
fprintf(stderr, "Multicast group must be given before interface.\n");
exit(EXIT_FAILURE);
}
join_mcast(sock, mgroup_addr, optarg);
iface_set = true;
last_ifindex = if_nametoindex(optarg);
if(!join_mcast(sock, mgroup_addr, last_ifindex)) {
fprintf(stderr, "Could not join multicast group on %s: ", optarg);
last_ifindex = 0;
}
break;
case 't':
if (!iface_set) {
fprintf(stderr, "Interface must be given before max response delay.\n");
exit(EXIT_FAILURE);
}
uint64_t max_multicast_delay = UINT64_C(1000) * strtoul(optarg, &endptr, 10);
if (!*optarg || *endptr || max_multicast_delay > INT64_MAX) {
fprintf(stderr, "Invalid multicast delay\n");
exit(EXIT_FAILURE);
}
if (last_ifindex) {
// insert the interface delay info at the beginning of the list
struct interface_delay_info **head = &if_delay_info_list;
struct interface_delay_info *old_head = if_delay_info_list;
*head = malloc(sizeof(*if_delay_info_list));
(*head)->ifindex = last_ifindex;
(*head)->max_multicast_delay = max_multicast_delay;
(*head)->next = old_head;
}
break;
case 'd':
@ -443,8 +672,19 @@ int main(int argc, char **argv) {
load_providers();
while (true)
serve(sock);
struct request_schedule schedule = {};
while (true) {
accept_request(&schedule, sock, if_delay_info_list);
struct request_task *task = schedule_pop_request(&schedule);
if (!task)
continue;
serve_request(task, sock);
free(task);
}
return EXIT_FAILURE;
}