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Run mDNS over IPv6, too #69

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Run mDNS over IPv6, too #69

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76b2ec3
libmdnsd: Remove superflous code
fzs Oct 5, 2022
b2863df
libmdnsd: Process messages from/to IPv4 and IPv6 destinations
fzs Oct 5, 2022
d2bc2b5
mquery: Adjust to new `mdnsd_in/_out` interface with sockaddr_storage
fzs Oct 5, 2022
ba0524f
libmdnsd: Add INFO message when sending queries
fzs Oct 5, 2022
06450eb
Provide mdns_sock for IPv4 and IPv6
fzs Oct 10, 2022
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140 changes: 98 additions & 42 deletions libmdnsd/mdnsd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,17 @@
* cached
*/

/* Sockaddr structure with sin_addr and sin6_addr union, to save the
extra storage requirements of a sockaddr_storage in smaller systems. */
struct sockaddr46 {
sa_family_t family;
in_port_t port;
union {
struct in_addr sin_addr;
struct in6_addr sin6_addr;
};
};

struct query {
char *name;
int type;
Expand All @@ -64,8 +75,7 @@ struct query {

struct unicast {
int id;
struct in_addr to;
unsigned short port;
struct sockaddr46 to;
mdns_record_t *r;
struct unicast *next;
};
Expand Down Expand Up @@ -320,7 +330,7 @@ static void _r_send(mdns_daemon_t *d, mdns_record_t *r)
}

/* Create generic unicast response struct */
static void _u_push(mdns_daemon_t *d, mdns_record_t *r, int id, struct in_addr to, unsigned short port)
static void _u_push(mdns_daemon_t *d, mdns_record_t *r, int id, const struct sockaddr46 *to)
{
struct unicast *u;

Expand All @@ -330,8 +340,7 @@ static void _u_push(mdns_daemon_t *d, mdns_record_t *r, int id, struct in_addr t

u->r = r;
u->id = id;
u->to = to;
u->port = port;
u->to = *to;
u->next = d->uanswers;
d->uanswers = u;
}
Expand Down Expand Up @@ -501,7 +510,7 @@ static void _gc(mdns_daemon_t *d)
d->expireall = (unsigned long)(d->now.tv_sec + GC);
}

static int _cache(mdns_daemon_t *d, struct resource *r, struct in_addr ip)
static int _cache(mdns_daemon_t *d, struct resource *r, const struct sockaddr46 *ips)
{
unsigned long int ttl;
struct cached *c = 0;
Expand Down Expand Up @@ -587,7 +596,11 @@ static int _cache(mdns_daemon_t *d, struct resource *r, struct in_addr ip)
case QTYPE_CNAME:
case QTYPE_PTR:
c->rr.rdname = strdup(r->known.ns.name);
c->rr.ip = ip;
if (ips->family == AF_INET) {
c->rr.ip = ips->sin_addr;
} else {
c->rr.ip6 = ips->sin6_addr;
}
break;

case QTYPE_SRV:
Expand Down Expand Up @@ -855,16 +868,30 @@ void mdnsd_register_receive_callback(mdns_daemon_t *d, mdnsd_record_received_cal
d->received_callback_data = data;
}

int mdnsd_in(mdns_daemon_t *d, struct message *m, struct in_addr ip, unsigned short port)
int mdnsd_in(mdns_daemon_t *d, struct message *m, const struct sockaddr_storage *ss_from)
{
mdns_record_t *r = NULL;
struct sockaddr46 from = { 0 };
int i, j;

if (d->shutdown)
return 1;

gettimeofday(&d->now, 0);

if (ss_from->ss_family == AF_INET) {
from.family = AF_INET;
from.port = ((struct sockaddr_in*)ss_from)->sin_port;
from.sin_addr = ((struct sockaddr_in*)ss_from)->sin_addr;
} else if (ss_from->ss_family == AF_INET6) {
from.family = AF_INET6;
from.port = ((struct sockaddr_in6*)ss_from)->sin6_port;
from.sin6_addr = ((struct sockaddr_in6*)ss_from)->sin6_addr;
} else {
WARN("Unsupported protocol family in incoming packet: %d", ss_from->ss_family);
return -1;
}

if (m->header.qr == 0) {
/* Process each query */
for (i = 0; i < m->qdcount; i++) {
Expand Down Expand Up @@ -936,8 +963,8 @@ int mdnsd_in(mdns_daemon_t *d, struct message *m, struct in_addr ip, unsigned sh
}

/* Send the matching unicast reply */
if (!has_conflict && port != 5353)
_u_push(d, r_start, m->id, ip, port);
if (!has_conflict && ntohs(from.port) != 5353)
_u_push(d, r_start, m->id, &from);
}

return 0;
Expand All @@ -958,15 +985,16 @@ int mdnsd_in(mdns_daemon_t *d, struct message *m, struct in_addr ip, unsigned sh
r = _r_next(d, NULL, m->an[i].name, m->an[i].type);
if (r && r->unique && r->modified && _a_match(&m->an[i], &r->rr)) {
/* double check, is this actually from us, looped back? */
if (ip.s_addr == d->addr.s_addr)
if ((from.family == AF_INET && from.sin_addr.s_addr == d->addr.s_addr) ||
(from.family == AF_INET6 && IN6_ARE_ADDR_EQUAL(&(from.sin6_addr), &(d->addr_v6))) )
continue;
_conflict(d, r);
}

if (d->received_callback)
d->received_callback(&m->an[i], d->received_callback_data);

if (_cache(d, &m->an[i], ip) != 0) {
if (_cache(d, &m->an[i], &from) != 0) {
ERR("Failed caching answer, possibly too long packet, skipping.");
continue;
}
Expand All @@ -975,7 +1003,7 @@ int mdnsd_in(mdns_daemon_t *d, struct message *m, struct in_addr ip, unsigned sh
return 0;
}

int mdnsd_out(mdns_daemon_t *d, struct message *m, struct in_addr *ip, unsigned short *port)
int mdnsd_out(mdns_daemon_t *d, struct message *m, struct sockaddr_storage *to)
{
mdns_record_t *r;
int ret = 0;
Expand All @@ -984,28 +1012,56 @@ int mdnsd_out(mdns_daemon_t *d, struct message *m, struct in_addr *ip, unsigned
memset(m, 0, sizeof(struct message));

/* Defaults, multicast */
*port = htons(5353);
ip->s_addr = inet_addr("224.0.0.251");
if (to->ss_family == AF_INET) {
((struct sockaddr_in*)to)->sin_port = htons(5353);
inet_pton(AF_INET, "224.0.0.251", &(((struct sockaddr_in*)to)->sin_addr));
} else if (to->ss_family == AF_INET6) {
((struct sockaddr_in6*)to)->sin6_port = htons(5353);
inet_pton(AF_INET6, "FF02::FB", &(((struct sockaddr_in6*)to)->sin6_addr));
} else {
WARN("Unsupported outgoing protocol family requested: %d", to->ss_family);
return -1;
}
m->header.qr = 1;
m->header.aa = 1;

/* Send out individual unicast answers */
if (d->uanswers) {
struct unicast *u = d->uanswers;
struct unicast *prev = d->uanswers;

INFO("Send Unicast Answer: Name: %s, Type: %d", u->r->rr.name, u->r->rr.type);
/* Find a unicast answer that matches the currently handled protocol. */
while (u && u->to.family != to->ss_family) {
prev = u;
u = u->next;
}

d->uanswers = u->next;
*port = htons(u->port);
*ip = u->to;
m->id = u->id;
message_qd(m, u->r->rr.name, u->r->rr.type, d->class);
message_an(m, u->r->rr.name, u->r->rr.type, d->class, u->r->rr.ttl);
u->r->last_sent = d->now;
_a_copy(m, &u->r->rr);
free(u);
if (u != NULL) {
INFO("Send Unicast Answer: Name: %s, Type: %d", u->r->rr.name, u->r->rr.type);

return 1;
if (prev == d->uanswers) {
d->uanswers = u->next;
} else {
prev->next = u->next;
}
u->next = NULL;

if (to->ss_family == AF_INET) {
((struct sockaddr_in*)to)->sin_port = u->to.port;
((struct sockaddr_in*)to)->sin_addr = u->to.sin_addr;
} else {
((struct sockaddr_in6*)to)->sin6_port = u->to.port;
((struct sockaddr_in6*)to)->sin6_addr = u->to.sin6_addr;
}
m->id = u->id;
message_qd(m, u->r->rr.name, u->r->rr.type, d->class);
message_an(m, u->r->rr.name, u->r->rr.type, d->class, u->r->rr.ttl);
u->r->last_sent = d->now;
_a_copy(m, &u->r->rr);
free(u);

return 1;
}
}

/* Accumulate any immediate responses */
Expand Down Expand Up @@ -1131,8 +1187,10 @@ int mdnsd_out(mdns_daemon_t *d, struct message *m, struct in_addr *ip, unsigned

/* Ask questions first, track nextbest time */
for (q = d->qlist; q != 0; q = q->list) {
if (q->nexttry > 0 && q->nexttry <= (unsigned long)d->now.tv_sec && q->tries < 3)
if (q->nexttry > 0 && q->nexttry <= (unsigned long)d->now.tv_sec && q->tries < 3) {
INFO("Send query for: Name: %s, Type: %d", q->name, q->type);
message_qd(m, q->name, q->type, d->class);
}
else if (q->nexttry > 0 && (nextbest == 0 || q->nexttry < nextbest))
nextbest = q->nexttry;
}
Expand Down Expand Up @@ -1460,8 +1518,8 @@ void mdnsd_set_srv(mdns_daemon_t *d, mdns_record_t *r, unsigned short priority,
static int process_in(mdns_daemon_t *d, int sd)
{
static unsigned char buf[MAX_PACKET_LEN + 1];
struct sockaddr_in from;
socklen_t ssize = sizeof(struct sockaddr_in);
struct sockaddr_storage from;
socklen_t ssize = sizeof(struct sockaddr_storage);
ssize_t bsize;

memset(buf, 0, sizeof(buf));
Expand All @@ -1476,9 +1534,7 @@ static int process_in(mdns_daemon_t *d, int sd)
rc = message_parse(&m, buf);
if (rc)
continue;
rc = mdnsd_in(d, &m, from.sin_addr, ntohs(from.sin_port));
if (rc)
continue;
mdnsd_in(d, &m, &from);
}

if (bsize < 0 && errno != EAGAIN)
Expand All @@ -1489,25 +1545,25 @@ static int process_in(mdns_daemon_t *d, int sd)

static int process_out(mdns_daemon_t *d, int sd)
{
unsigned short int port;
struct sockaddr_in to;
struct in_addr ip;
struct sockaddr_storage to = { 0 };
socklen_t ssize = sizeof(struct sockaddr_storage);
struct message m;

while (mdnsd_out(d, &m, &ip, &port)) {
if (getsockname(sd, (struct sockaddr*)&to, &ssize) != 0) {
WARN("Unable to determine address family of socket %d: %s", sd, strerror(errno));
return 1;
}

DBG("Processing %s (%d) socket %d, ssize %d", to.ss_family == AF_INET ? "IPv4" : "IPv6", to.ss_family, sd, ssize);
while (mdnsd_out(d, &m, &to) > 0) {
unsigned char *buf;
ssize_t len;

memset(&to, 0, sizeof(to));
to.sin_family = AF_INET;
to.sin_port = port;
to.sin_addr = ip;

len = message_packet_len(&m);
buf = message_packet(&m);
mdnsd_log_hex("Send Data:", buf, len);

if (sendto(sd, buf, len, MSG_DONTWAIT, (struct sockaddr *)&to, sizeof(struct sockaddr_in)) != len)
if (sendto(sd, buf, len, MSG_DONTWAIT, (struct sockaddr *)&to, ssize) != len)
return 2;
}

Expand Down
17 changes: 12 additions & 5 deletions libmdnsd/mdnsd.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -153,13 +153,20 @@ void mdnsd_register_receive_callback(mdns_daemon_t *d, mdnsd_record_received_cal
/**
* Oncoming message from host (to be cached/processed)
*/
int mdnsd_in(mdns_daemon_t *d, struct message *m, struct in_addr ip, unsigned short port);
int mdnsd_in(mdns_daemon_t *d, struct message *m, const struct sockaddr_storage *from);

/**
* Outgoing messge to be delivered to host, returns >0 if one was
* returned and m/ip/port set
*/
int mdnsd_out(mdns_daemon_t *d, struct message *m, struct in_addr *ip, unsigned short *port);
* Outgoing message passed to the host for delivery to destination.
*
* @param[out] m Message filled in to be sent by teh host
* @param[in,out] to The sockaddr_storage needs to have the family member set to
* the protocol family over which the message should be sent.
* When processing a IPv4 socket it must be set to AF_INET and
* when processing a IPv6 socket it must be set to AF_INET6.
* The function fills in the destination port and IP address.
* @return >0 if a message was returned and m/ip/port set, <0 in case of error
*/
int mdnsd_out(mdns_daemon_t *d, struct message *m, struct sockaddr_storage *to);

/**
* returns the max wait-time until mdnsd_out() needs to be called again
Expand Down
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