commit 0051057605aa1681a5e6144f0f590d78d842686a Author: Darell Tan Date: Sun Apr 10 21:51:52 2011 +0800 Initial commit. diff --git a/.hgignore b/.hgignore new file mode 100644 index 0000000..50629aa --- /dev/null +++ b/.hgignore @@ -0,0 +1,4 @@ +syntax: glob + +*.a +*.o diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..8ef9e34 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,457 @@ + GNU LESSER GENERAL PUBLIC LICENSE + Version 2.1, February 1999 + + Copyright (C) 1991, 1999 Free Software Foundation, Inc. + 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + +[This is the first released version of the Lesser GPL. It also counts + as the successor of the GNU Library Public License, version 2, hence + the version number 2.1.] + + Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. 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Its other goal is to be extremely +small, embeddable, and have no external dependencies. + +It only answers queries related to its own hostname (the A record), the +service PTRs, and the "_services.dns-sd._udp.local" name, which advertises +all services on a particular host. + +Services consist of a single SRV and TXT record. + +Decoding of MDNS packets is only done to retrieve the questions and answer RRs. +The purpose for decoding answer RRs is to make sure the service PTR is not +sent out if it is already included in the answer RRs. + +It also only utilizes multicast packets, so no "QU" queries are accepted. + +There is no name collision detection, so this means no queries are generated +before publishing the services. However compliant responders will avoid using +our names, since the implementation will respond to queries that match our +name. + + +TODO +----- + * better, more stable & complete API + * name collision detection + + +FILES +------ + * mdns.c - provides data structures, parsing & encoding of MDNS packets + * mdnsd.c - implements the server socket, communication and thread + * testmdnsd.c - an example that creates an instance until terminated + + +LICENSE +-------- +Copyright (C) 2011 Darell Tan + +This library is free software; you can redistribute it and/or +modify it under the terms of the GNU Lesser General Public +License as published by the Free Software Foundation; either +version 2.1 of the License, or (at your option) any later version. + +This library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Lesser General Public License for more details. + +You should have received a copy of the GNU Lesser General Public +License along with this library; if not, write to the Free Software +Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + diff --git a/mdns.c b/mdns.c new file mode 100644 index 0000000..75e7314 --- /dev/null +++ b/mdns.c @@ -0,0 +1,871 @@ +/* + * tinysvcmdns - a tiny MDNS implementation for publishing services + * Copyright (C) 2011 Darell Tan + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include "mdns.h" +#include +#include +#include +#include +#include +#include + + +#define DEFAULT_TTL 120 + + +struct name_comp { + uint8_t *label; // label + size_t pos; // position in msg + + struct name_comp *next; +}; + +// ----- label functions ----- + +// compares 2 names +static inline int cmp_nlabel(const uint8_t *L1, const uint8_t *L2) { + return strcmp((char *) L1, (char *) L2); +} + +// duplicates a name +inline uint8_t *dup_nlabel(const uint8_t *n) { + assert(n[0] <= 63); // prevent mis-use + return (uint8_t *) strdup((char *) n); +} + +// duplicates a label +uint8_t *dup_label(const uint8_t *label) { + int len = *label + 1; + if (len > 63) + return NULL; + uint8_t *newlabel = malloc(len + 1); + strncpy((char *) newlabel, (char *) label, len); + newlabel[len] = '\0'; + return newlabel; +} + +uint8_t *join_nlabel(const uint8_t *n1, const uint8_t *n2) { + int len1, len2; + uint8_t *s; + + assert(n1[0] <= 63 && n2[0] <= 63); // detect misuse + + len1 = strlen((char *) n1); + len2 = strlen((char *) n2); + + s = malloc(len1 + len2 + 1); + strncpy((char *) s, (char *) n1, len1); + strncpy((char *) s+len1, (char *) n2, len2); + s[len1 + len2] = '\0'; + return s; +} + +// returns a human-readable name label in dotted form +char *nlabel_to_str(const uint8_t *name) { + char *label, *labelp; + const uint8_t *p; + + assert(name != NULL); + + label = labelp = malloc(256); + + for (p = name; *p; p++) { + strncpy(labelp, (char *) p + 1, *p); + labelp += *p; + *labelp = '.'; + labelp++; + + p += *p; + } + + *labelp = '\0'; + + return label; +} + +// returns the length of a label field +// does NOT uncompress the field, so it could be as small as 2 bytes +// or 1 for the root +static size_t label_len(uint8_t *pkt_buf, size_t pkt_len, size_t off) { + uint8_t *p; + uint8_t *e = pkt_buf + pkt_len; + size_t len = 0; + + for (p = pkt_buf + off; p < e; p++) { + if (*p == 0) { + return len + 1; + } else if ((*p & 0xC0) == 0xC0) { + return len + 2; + } else { + len += *p + 1; + p += *p; + } + } + + return len; +} + +// creates a label +// free() after use +uint8_t *create_label(const char *txt) { + int len; + uint8_t *s; + + assert(txt != NULL); + len = strlen(txt); + if (len > 63) + return NULL; + + s = malloc(len + 2); + s[0] = len; + strncpy((char *) s + 1, txt, len); + s[len + 1] = '\0'; + + return s; +} + +// creates a uncompressed name label given a DNS name like "apple.b.com" +// free() after use +uint8_t *create_nlabel(const char *name) { + char *label; + char *p, *e, *lenpos; + int len = 0; + + assert(name != NULL); + + len = strlen(name); + label = malloc(len + 1 + 1); + if (label == NULL) + return NULL; + + strncpy((char *) label + 1, name, len); + label[len + 1] = '\0'; + + p = label; + e = p + len; + lenpos = p; + + while (p < e) { + *lenpos = 0; + char *dot = memchr(p + 1, '.', e - p - 1); + if (dot == NULL) + dot = e + 1; + *lenpos = dot - p - 1; + + p = dot; + lenpos = dot; + } + + return (uint8_t *) label; +} + +// copies a label from the buffer into a newly-allocated string +// free() after use +static uint8_t *copy_label(uint8_t *pkt_buf, size_t pkt_len, size_t off) { + int len; + + if (off > pkt_len) + return NULL; + + len = pkt_buf[off] + 1; + if (off + len > pkt_len) { + DEBUG_PRINTF("label length exceeds packet buffer\n"); + return NULL; + } + + return dup_label(pkt_buf + off); +} + +// uncompresses a name +// free() after use +static uint8_t *uncompress_nlabel(uint8_t *pkt_buf, size_t pkt_len, size_t off) { + uint8_t *p; + uint8_t *e = pkt_buf + pkt_len; + size_t len = 0; + char *str, *sp; + if (off >= pkt_len) + return NULL; + + // calculate length of uncompressed label + for (p = pkt_buf + off; *p && p < e; p++) { + size_t llen = 0; + if ((*p & 0xC0) == 0xC0) { + uint8_t *p2 = pkt_buf + (((p[0] & ~0xC0) << 8) | p[1]); + llen = *p2 + 1; + p = p2 + llen - 1; + } else { + llen = *p + 1; + p += llen - 1; + } + len += llen; + } + + str = sp = malloc(len + 1); + if (str == NULL) + return NULL; + + // FIXME: must merge this with above code + for (p = pkt_buf + off; *p && p < e; p++) { + size_t llen = 0; + if ((*p & 0xC0) == 0xC0) { + uint8_t *p2 = pkt_buf + (((p[0] & ~0xC0) << 8) | p[1]); + llen = *p2 + 1; + strncpy(sp, (char *) p2, llen); + p = p2 + llen - 1; + } else { + llen = *p + 1; + strncpy(sp, (char *) p, llen); + p += llen - 1; + } + sp += llen; + } + *sp = '\0'; + + return (uint8_t *) str; +} + +// ----- RR list & group functions ----- + +void rr_entry_destroy(struct rr_entry *rr) { + struct rr_data_txt *txt_rec; + assert(rr); + + // check rr_type and free data elements + switch (rr->type) { + case RR_PTR: + if (rr->data.PTR.name) + free(rr->data.PTR.name); + // don't free entry + break; + + case RR_TXT: + txt_rec = &rr->data.TXT; + while (txt_rec) { + struct rr_data_txt *next = txt_rec->next; + if (txt_rec->txt) + free(txt_rec->txt); + + // only free() if it wasn't part of the struct + if (txt_rec != &rr->data.TXT) + free(txt_rec); + + txt_rec = next; + } + break; + + case RR_SRV: + if (rr->data.SRV.target) + free(rr->data.SRV.target); + break; + + default: + // nothing to free + break; + } + + free(rr->name); + free(rr); +} + +// destroys an RR list (and optionally, items) +void rr_list_destroy(struct rr_list *rr, char destroy_items) { + struct rr_list *rr_next; + + for (; rr; rr = rr_next) { + rr_next = rr->next; + if (destroy_items) + rr_entry_destroy(rr->e); + free(rr); + } +} + +int rr_list_count(struct rr_list *rr) { + int i = 0; + for (; rr; i++, rr = rr->next); + return i; +} + +struct rr_entry *rr_list_remove(struct rr_list **rr_head, struct rr_entry *rr) { + struct rr_list *le = *rr_head, *pe = NULL; + for (; le; le = le->next) { + if (le->e == rr) { + if (pe == NULL) { + *rr_head = le->next; + free(le); + return rr; + } else { + pe->next = le->next; + free(le); + return rr; + } + } + pe = le; + } + return NULL; +} + +// appends an rr_entry to an RR list +// if the RR is already in the list, it will not be added +// RRs are compared by memory location - not its contents +// return value of 0 means item not added +int rr_list_append(struct rr_list **rr_head, struct rr_entry *rr) { + struct rr_list *node = malloc(sizeof(struct rr_list)); + node->e = rr; + node->next = NULL; + + if (*rr_head == NULL) { + *rr_head = node; + } else { + struct rr_list *e = *rr_head, *taile; + for (; e; e = e->next) { + // already in list - don't add + if (e->e == rr) { + free(node); + return 0; + } + if (e->next == NULL) + taile = e; + } + taile->next = node; + } + return 1; +} + +#define FILL_RR_ENTRY(rr, _name, _type) \ + rr->name = _name; \ + rr->type = _type; \ + rr->ttl = DEFAULT_TTL; \ + rr->cache_flush = 1; \ + rr->rr_class = 1; + +struct rr_entry *rr_create_a(uint8_t *name, uint32_t addr) { + DECL_MALLOC_ZERO_STRUCT(rr, rr_entry); + FILL_RR_ENTRY(rr, name, RR_A); + rr->data.A.addr = addr; + return rr; +} + +struct rr_entry *rr_create_srv(uint8_t *name, uint16_t port, uint8_t *target) { + DECL_MALLOC_ZERO_STRUCT(rr, rr_entry); + FILL_RR_ENTRY(rr, name, RR_SRV); + rr->data.SRV.port = port; + rr->data.SRV.target = target; + return rr; +} + +struct rr_entry *rr_create_ptr(uint8_t *name, struct rr_entry *d_rr) { + DECL_MALLOC_ZERO_STRUCT(rr, rr_entry); + FILL_RR_ENTRY(rr, name, RR_PTR); + rr->data.PTR.entry = d_rr; + return rr; +} + +struct rr_entry *rr_create(uint8_t *name, enum rr_type type) { + DECL_MALLOC_ZERO_STRUCT(rr, rr_entry); + FILL_RR_ENTRY(rr, name, type); + return rr; +} + +void rr_set_nsec(struct rr_entry *rr_nsec, enum rr_type type) { + assert(rr_nsec->type = RR_NSEC); + assert((type / 8) < sizeof(rr_nsec->data.NSEC.bitmap)); + + rr_nsec->data.NSEC.bitmap[ type / 8 ] = 1 << (7 - (type % 8)); +} + +void rr_add_txt(struct rr_entry *rr_txt, const char *txt) { + struct rr_data_txt *txt_rec; + assert(rr_txt->type == RR_TXT); + + txt_rec = &rr_txt->data.TXT; + + // is current data filled? + if (txt_rec->txt == NULL) { + txt_rec->txt = create_label(txt); + return; + } + + // find the last node + for (; txt_rec->next; txt_rec = txt_rec->next); + + // create a new empty node + txt_rec->next = malloc(sizeof(struct rr_data_txt)); + + txt_rec = txt_rec->next; + txt_rec->txt = create_label(txt); + txt_rec->next = NULL; +} + +// adds a record to an rr_group +void rr_group_add(struct rr_group **group, struct rr_entry *rr) { + struct rr_group *g; + + assert(rr != NULL); + + if (*group) { + g = rr_group_find(*group, rr->name); + if (g) { + rr_list_append(&g->rr, rr); + return; + } + } + + MALLOC_ZERO_STRUCT(g, rr_group); + g->name = dup_nlabel(rr->name); + rr_list_append(&g->rr, rr); + + // prepend to list + g->next = *group; + *group = g; +} + +// finds a rr_group matching the given name +struct rr_group *rr_group_find(struct rr_group* g, uint8_t *name) { + for (; g; g = g->next) { + if (cmp_nlabel(g->name, name) == 0) + return g; + } + return NULL; +} + +struct rr_entry *rr_entry_find(struct rr_list *rr_list, uint8_t *name, uint16_t type) { + struct rr_list *rr = rr_list; + for (; rr; rr = rr->next) { + if (rr->e->type == type) + return rr->e; + } + return NULL; +} + +void rr_group_destroy(struct rr_group *group) { + struct rr_group *g = group; + + while (g) { + struct rr_group *nextg = g->next; + free(g->name); + rr_list_destroy(g->rr, 1); + free(g); + g = nextg; + } +} + +// initialize the packet for reply +// clears the packet of list structures but not its list items +void mdns_init_reply(struct mdns_pkt *pkt, uint16_t id) { + // copy transaction ID + pkt->id = id; + + // response flags + pkt->flags = MDNS_FLAG_RESP | MDNS_FLAG_AA; + + rr_list_destroy(pkt->rr_qn, 0); + rr_list_destroy(pkt->rr_ans, 0); + rr_list_destroy(pkt->rr_auth, 0); + rr_list_destroy(pkt->rr_add, 0); + + pkt->rr_qn = NULL; + pkt->rr_ans = NULL; + pkt->rr_auth = NULL; + pkt->rr_add = NULL; + + pkt->num_qn = 0; + pkt->num_ans_rr = 0; + pkt->num_auth_rr = 0; + pkt->num_add_rr = 0; +} + +// destroys an mdns_pkt struct, including its contents +void mdns_pkt_destroy(struct mdns_pkt *p) { + rr_list_destroy(p->rr_qn, 1); + rr_list_destroy(p->rr_ans, 1); + rr_list_destroy(p->rr_auth, 1); + rr_list_destroy(p->rr_add, 1); + + free(p); +} + + +// parse the MDNS questions section +// stores the parsed data in the given mdns_pkt struct +static size_t mdns_parse_qn(uint8_t *pkt_buf, size_t pkt_len, size_t off, + struct mdns_pkt *pkt) { + const uint8_t *p = pkt_buf + off; + struct rr_entry *rr; + uint8_t *name; + + assert(pkt != NULL); + + rr = malloc(sizeof(struct rr_entry)); + memset(rr, 0, sizeof(struct rr_entry)); + + name = uncompress_nlabel(pkt_buf, pkt_len, off); + p += label_len(pkt_buf, pkt_len, off); + rr->name = name; + + rr->type = ntohs( * (uint16_t *) p ); + p += sizeof(uint16_t); + + rr->unicast_query = (*p & 0x80) == 0x80; + rr->rr_class = ntohs( * (uint16_t *) p) & ~0x80; + p += sizeof(uint16_t); + + rr_list_append(&pkt->rr_qn, rr); + + return p - (pkt_buf + off); +} + +// parse the MDNS RR section +// stores the parsed data in the given mdns_pkt struct +static size_t mdns_parse_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off, + struct mdns_pkt *pkt) { + const uint8_t *p = pkt_buf + off; + const uint8_t *e = pkt_buf + pkt_len; + struct rr_entry *rr; + uint8_t *name; + size_t rr_data_len = 0; + struct rr_data_txt *txt_rec; + + assert(pkt != NULL); + + if (off > pkt_len) + return 0; + + rr = malloc(sizeof(struct rr_entry)); + memset(rr, 0, sizeof(struct rr_entry)); + + name = uncompress_nlabel(pkt_buf, pkt_len, off); + p += label_len(pkt_buf, pkt_len, off); + rr->name = name; + + rr->type = ntohs( * (uint16_t *) p ); + p += sizeof(uint16_t); + + rr->cache_flush = (*p & 0x80) == 0x80; + rr->rr_class = ntohs( * (uint16_t *) p) & ~0x80; + p += sizeof(uint16_t); + + rr->ttl = ntohl( * (uint32_t *) p ); + p += sizeof(uint32_t); + + // RR data + rr_data_len = ntohs( * (uint16_t *) p ); + p += sizeof(uint16_t); + e = p + rr_data_len; + + // see if we can parse the RR data + switch (rr->type) { + case RR_A: + rr->data.A.addr = ntohl( * (uint32_t *) p ); + p += sizeof(uint32_t); + break; + + case RR_PTR: + rr->data.PTR.name = uncompress_nlabel(pkt_buf, pkt_len, p - pkt_buf); + p += rr_data_len; + break; + + case RR_TXT: + txt_rec = &rr->data.TXT; + while (1) { + txt_rec->txt = copy_label(pkt_buf, pkt_len, p - pkt_buf); + p += txt_rec->txt[0] + 1; + + if (p >= e) + break; + + // allocate another record + txt_rec->next = malloc(sizeof(struct rr_data_txt)); + txt_rec = txt_rec->next; + txt_rec->next = NULL; + } + break; + + default: + // skip to end of RR data + p = e; + } + + rr_list_append(&pkt->rr_ans, rr); + + return p - (pkt_buf + off); +} + +// parse a MDNS packet into an mdns_pkt struct +struct mdns_pkt *mdns_parse_pkt(uint8_t *pkt_buf, size_t pkt_len) { + uint16_t *p = (uint16_t *) pkt_buf; + size_t off; + struct mdns_pkt *pkt; + int i; + + if (pkt_len < 12) + return NULL; + + MALLOC_ZERO_STRUCT(pkt, mdns_pkt); + + // parse header + pkt->id = ntohs(*p); p++; + pkt->flags = ntohs(*p); p++; + pkt->num_qn = ntohs(*p); p++; + pkt->num_ans_rr = ntohs(*p); p++; + pkt->num_auth_rr = ntohs(*p); p++; + pkt->num_add_rr = ntohs(*p); p++; + + off = (uint8_t *) p - pkt_buf; + + // parse questions + for (i = 0; i < pkt->num_qn; i++) { + size_t l = mdns_parse_qn(pkt_buf, pkt_len, off, pkt); + if (! l) { + DEBUG_PRINTF("error parsing question #%d\n", i); + mdns_pkt_destroy(pkt); + return NULL; + } + + off += l; + } + + // parse answer RRs + for (i = 0; i < pkt->num_ans_rr; i++) { + size_t l = mdns_parse_rr(pkt_buf, pkt_len, off, pkt); + if (! l) { + DEBUG_PRINTF("error parsing answer #%d\n", i); + mdns_pkt_destroy(pkt); + return NULL; + } + + off += l; + } + + // TODO: parse the authority and additional RR sections + + return pkt; +} + +// encodes a name (label) into a packet using the name compression scheme +// encoded names will be added to the compression list for subsequent use +static size_t mdns_encode_name(uint8_t *pkt_buf, size_t pkt_len, size_t off, + const uint8_t *name, struct name_comp *comp) { + struct name_comp *c, *c_tail = NULL; + uint8_t *p = pkt_buf + off; + size_t len = 0; + + if (name) { + while (*name) { + // find match for compression + for (c = comp; c; c = c->next) { + if (cmp_nlabel(name, c->label) == 0) { + *(uint16_t *) p = htons(0xC000 | (c->pos & ~0xC000)); + return len + sizeof(uint16_t); + } + + if (c->next == NULL) + c_tail = c; + } + + // copy this segment + int segment_len = *name + 1; + strncpy((char *) p, (char *) name, segment_len); + + // cache the name for subsequent compression + DECL_MALLOC_ZERO_STRUCT(new_c, name_comp); + + new_c->label = (uint8_t *) name; + new_c->pos = p - pkt_buf; + c_tail->next = new_c; + + // advance to next name segment + p += segment_len; + len += segment_len; + name += segment_len; + } + } + + *p = '\0'; // root "label" + len += 1; + + return len; +} + +// encodes an RR entry at the given offset +// returns the size of the entire RR entry +static size_t mdns_encode_rr(uint8_t *pkt_buf, size_t pkt_len, size_t off, + struct rr_entry *rr, struct name_comp *comp) { + uint8_t *p = pkt_buf + off, *p_data; + size_t l; + struct rr_data_txt *txt_rec; + uint8_t *label; + int i; + + assert(off < pkt_len); + + // name + l = mdns_encode_name(pkt_buf, pkt_len, off, rr->name, comp); + assert(l != 0); + p += l; + + // type + *(uint16_t *) p = htons(rr->type); + p += sizeof(uint16_t); + + // class & cache flush + *(uint16_t *) p = htons((rr->rr_class & ~0x8000) | (rr->cache_flush << 15)); + p += sizeof(uint16_t); + + // TTL + *(uint32_t *) p = htonl(rr->ttl); + p += sizeof(uint32_t); + + // data length (filled in later) + p += sizeof(uint16_t); + + // start of data marker + p_data = p; + + switch (rr->type) { + case RR_A: + *(uint32_t *) p = (rr->data.A.addr); + p += sizeof(uint32_t); + break; + + case RR_PTR: + label = rr->data.PTR.name ? + rr->data.PTR.name : + rr->data.PTR.entry->name; + p += mdns_encode_name(pkt_buf, pkt_len, p - pkt_buf, label, comp); + break; + + case RR_TXT: + txt_rec = &rr->data.TXT; + for (; txt_rec; txt_rec = txt_rec->next) { + int len = txt_rec->txt[0] + 1; + strncpy((char *) p, (char *) txt_rec->txt, len); + p += len; + } + break; + + case RR_SRV: + *(uint16_t *) p = htons(rr->data.SRV.priority); + p += sizeof(uint16_t); + + *(uint16_t *) p = htons(rr->data.SRV.weight); + p += sizeof(uint16_t); + + *(uint16_t *) p = htons(rr->data.SRV.port); + p += sizeof(uint16_t); + + p += mdns_encode_name(pkt_buf, pkt_len, p - pkt_buf, + rr->data.SRV.target, comp); + break; + + case RR_NSEC: + p += mdns_encode_name(pkt_buf, pkt_len, p - pkt_buf, + rr->name, comp); + + *p++ = 0; // bitmap window/block number + + *p++ = sizeof(rr->data.NSEC.bitmap); // bitmap length + + for (i = 0; i < sizeof(rr->data.NSEC.bitmap); i++) + *p++ = rr->data.NSEC.bitmap[i]; + + break; + + default: + DEBUG_PRINTF("unhandled rr type 0x%02x\n", rr->type); + } + + // calculate data length based on p + l = p - p_data; + + // fill in the length + *(uint16_t *) (p - l - sizeof(uint16_t)) = htons(l); + + return p - pkt_buf - off; +} + +// encodes a MDNS packet from the given mdns_pkt struct into a buffer +// returns the size of the entire MDNS packet +size_t mdns_encode_pkt(struct mdns_pkt *answer, uint8_t *pkt_buf, size_t pkt_len) { + struct name_comp *comp; + uint16_t *p = (uint16_t *) pkt_buf; + //uint8_t *e = pkt_buf + pkt_len; + size_t off; + int i; + + assert(answer != NULL); + assert(pkt_len >= 12); + + if (p == NULL) + return -1; + + // this is an Answer - number of qns should be zero + assert(answer->num_qn == 0); + + *p++ = htons(answer->id); + *p++ = htons(answer->flags); + *p++ = htons(answer->num_qn); + *p++ = htons(answer->num_ans_rr); + *p++ = htons(answer->num_auth_rr); + *p++ = htons(answer->num_add_rr); + + off = (uint8_t *) p - pkt_buf; + + // allocate list for name compression + comp = malloc(sizeof(struct name_comp)); + if (comp == NULL) + return -1; + memset(comp, 0, sizeof(struct name_comp)); + + // dummy entry + comp->label = (uint8_t *) ""; + comp->pos = 0; + + // skip encoding of qn + + struct rr_list *rr_set[] = { + answer->rr_ans, + answer->rr_auth, + answer->rr_add + }; + + // encode answer, authority and additional RRs + for (i = 0; i < sizeof(rr_set) / sizeof(rr_set[0]); i++) { + struct rr_list *rr = rr_set[i]; + for (; rr; rr = rr->next) { + size_t l = mdns_encode_rr(pkt_buf, pkt_len, off, rr->e, comp); + off += l; + + if (off >= pkt_len) { + DEBUG_PRINTF("packet buffer too small\n"); + return -1; + } + } + + } + + // free name compression list + while (comp) { + struct name_comp *c = comp->next; + free(comp); + comp = c; + } + + return off; +} + diff --git a/mdns.h b/mdns.h new file mode 100644 index 0000000..afd7474 --- /dev/null +++ b/mdns.h @@ -0,0 +1,169 @@ +/* + * tinysvcmdns - a tiny MDNS implementation for publishing services + * Copyright (C) 2011 Darell Tan + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef __MDNS_H__ +#define __MDNS_H__ + +#include +#include + +#define MALLOC_ZERO_STRUCT(x, type) \ + x = malloc(sizeof(struct type)); \ + memset(x, 0, sizeof(struct type)); + +#define DECL_MALLOC_ZERO_STRUCT(x, type) \ + struct type * MALLOC_ZERO_STRUCT(x, type) + +#ifndef NDEBUG + #define DEBUG_PRINTF(...) printf(__VA_ARGS__) +#else + #define DEBUG_PRINTF(...) ((void) 0) +#endif + + +struct rr_data_srv { + uint16_t priority; + uint16_t weight; + uint16_t port; + uint8_t *target; // host +}; + +struct rr_data_txt { + struct rr_data_txt *next; + uint8_t *txt; +}; + +struct rr_data_nsec { + //uint8_t *name; // same as record + + // NSEC occupies the 47th bit, 5 bytes + //uint8_t bitmap_len; // = 5 + uint8_t bitmap[5]; // network order: first byte contains LSB +}; + +struct rr_data_ptr { + uint8_t *name; // NULL if entry is to be used + struct rr_entry *entry; +}; + +struct rr_data_a { + uint32_t addr; +}; + +struct rr_entry { + uint8_t *name; + + enum rr_type { + RR_A = 0x01, + RR_PTR = 0x0C, + RR_TXT = 0x10, + RR_AAAA = 0x1C, + RR_SRV = 0x21, + RR_NSEC = 0x2F, + RR_ANY = 0xFF, + } type; + + uint32_t ttl; + + // for use in Questions only + char unicast_query; + + // for use in Answers only + char cache_flush; + + uint16_t rr_class; + + // RR data + union { + struct rr_data_nsec NSEC; + struct rr_data_srv SRV; + struct rr_data_txt TXT; + struct rr_data_ptr PTR; + struct rr_data_a A; + } data; +}; + +struct rr_list { + struct rr_entry *e; + struct rr_list *next; +}; + +struct rr_group { + uint8_t *name; + + struct rr_list *rr; + + struct rr_group *next; +}; + +#define MDNS_FLAG_RESP (1 << 15) // Query=0 / Response=1 +#define MDNS_FLAG_AA (1 << 10) // Authoritative +#define MDNS_FLAG_TC (1 << 9) // TrunCation +#define MDNS_FLAG_RD (1 << 8) // Recursion Desired +#define MDNS_FLAG_RA (1 << 7) // Recursion Available +#define MDNS_FLAG_Z (1 << 6) // Reserved (zero) + +#define MDNS_FLAG_GET_RCODE(x) (x & 0x0F) +#define MDNS_FLAG_GET_OPCODE(x) ((x >> 11) & 0x0F) + +struct mdns_pkt { + uint16_t id; // transaction ID + uint16_t flags; + uint16_t num_qn; + uint16_t num_ans_rr; + uint16_t num_auth_rr; + uint16_t num_add_rr; + + struct rr_list *rr_qn; // questions + struct rr_list *rr_ans; // answer RRs + struct rr_list *rr_auth; // authority RRs + struct rr_list *rr_add; // additional RRs +}; + +struct mdns_pkt *mdns_parse_pkt(uint8_t *pkt_buf, size_t pkt_len); + +void mdns_init_reply(struct mdns_pkt *pkt, uint16_t id); +size_t mdns_encode_pkt(struct mdns_pkt *answer, uint8_t *pkt_buf, size_t pkt_len); + +void mdns_pkt_destroy(struct mdns_pkt *p); +void rr_group_destroy(struct rr_group *group); +struct rr_group *rr_group_find(struct rr_group *g, uint8_t *name); +struct rr_entry *rr_entry_find(struct rr_list *rr_list, uint8_t *name, uint16_t type); +void rr_group_add(struct rr_group **group, struct rr_entry *rr); + +int rr_list_count(struct rr_list *rr); +int rr_list_append(struct rr_list **rr_head, struct rr_entry *rr); +struct rr_entry *rr_list_remove(struct rr_list **rr_head, struct rr_entry *rr); +void rr_list_destroy(struct rr_list *rr, char destroy_items); + +struct rr_entry *rr_create_ptr(uint8_t *name, struct rr_entry *d_rr); +struct rr_entry *rr_create_srv(uint8_t *name, uint16_t port, uint8_t *target); +struct rr_entry *rr_create_a(uint8_t *name, uint32_t addr); +struct rr_entry *rr_create(uint8_t *name, enum rr_type type); +void rr_set_nsec(struct rr_entry *rr_nsec, enum rr_type type); +void rr_add_txt(struct rr_entry *rr_txt, const char *txt); + +uint8_t *create_label(const char *txt); +uint8_t *create_nlabel(const char *name); +char *nlabel_to_str(const uint8_t *name); +uint8_t *dup_label(const uint8_t *label); +uint8_t *dup_nlabel(const uint8_t *n); +uint8_t *join_nlabel(const uint8_t *n1, const uint8_t *n2); + +#endif /*!__MDNS_H__*/ diff --git a/mdnsd.c b/mdnsd.c new file mode 100644 index 0000000..1f6b916 --- /dev/null +++ b/mdnsd.c @@ -0,0 +1,555 @@ +/* + * tinysvcmdns - a tiny MDNS implementation for publishing services + * Copyright (C) 2011 Darell Tan + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "mdns.h" +#include "mdnsd.h" + +#define MDNS_ADDR "224.0.0.251" +#define MDNS_PORT 5353 + +#define PACKET_SIZE 65536 + +#define SERVICES_DNS_SD_NLABEL \ + ((uint8_t *) "\x09_services\x07_dns-sd\x04_udp\x05local") + +struct mdnsd { + pthread_mutex_t data_lock; + int sockfd; + int notify_pipe[2]; + int stop_flag; + + struct rr_group *group; + struct rr_list *announce; + struct rr_list *services; + uint8_t *hostname; +}; + +struct mdns_service { + struct rr_list *entries; +}; + +///////////////////////////////// + + +static void log_message(int loglevel, char *fmt_str, ...) { + va_list ap; + char buf[2048]; + + va_start(ap, fmt_str); + vsnprintf(buf, 2047, fmt_str, ap); + va_end(ap); + buf[2047] = 0; + + fprintf(stderr, "%s\n", buf); +} + +static int create_recv_sock() { + int sd = socket(AF_INET, SOCK_DGRAM, 0); + if (sd < 0) { + log_message(LOG_ERR, "recv socket(): %m"); + return sd; + } + + int r = -1; + + int on = 1; + if ((r = setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *) &on, sizeof(on))) < 0) { + log_message(LOG_ERR, "recv setsockopt(SO_REUSEADDR): %m"); + return r; + } + + /* bind to an address */ + struct sockaddr_in serveraddr; + memset(&serveraddr, 0, sizeof(serveraddr)); + serveraddr.sin_family = AF_INET; + serveraddr.sin_port = htons(MDNS_PORT); + serveraddr.sin_addr.s_addr = htonl(INADDR_ANY); /* receive multicast */ + if ((r = bind(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr))) < 0) { + log_message(LOG_ERR, "recv bind(): %m"); + } + + // add membership to receiving socket + struct ip_mreq mreq; + memset(&mreq, 0, sizeof(struct ip_mreq)); + mreq.imr_interface.s_addr = htonl(INADDR_ANY); + mreq.imr_multiaddr.s_addr = inet_addr(MDNS_ADDR); + if ((r = setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *) &mreq, sizeof(mreq))) < 0) { + log_message(LOG_ERR, "recv setsockopt(IP_ADD_MEMBERSHIP): %m"); + return r; + } + + // enable loopback in case someone else needs the data + if ((r = setsockopt(sd, IPPROTO_IP, IP_MULTICAST_LOOP, (char *) &on, sizeof(on))) < 0) { + log_message(LOG_ERR, "recv setsockopt(IP_MULTICAST_LOOP): %m"); + return r; + } + + +#ifdef IP_PKTINFO + if ((r = setsockopt(sd, SOL_IP, IP_PKTINFO, (char *) &on, sizeof(on))) < 0) { + log_message(LOG_ERR, "recv setsockopt(IP_PKTINFO): %m"); + return r; + } +#endif + + return sd; +} + +static ssize_t send_packet(int fd, const void *data, size_t len) { + static struct sockaddr_in toaddr; + if (toaddr.sin_family != AF_INET) { + memset(&toaddr, 0, sizeof(struct sockaddr_in)); + toaddr.sin_family = AF_INET; + toaddr.sin_port = htons(MDNS_PORT); + toaddr.sin_addr.s_addr = inet_addr(MDNS_ADDR); + } + + return sendto(fd, data, len, 0, (struct sockaddr *) &toaddr, sizeof(struct sockaddr_in)); +} + + +// populate the specified list which matches the RR name and type +// type can be RR_ANY, which populates all entries EXCEPT RR_NSEC +static int populate_answers(struct mdnsd *svr, struct rr_list **rr_head, uint8_t *name, enum rr_type type) { + int num_ans = 0; + struct rr_entry *rr; + + // check if we have the records + pthread_mutex_lock(&svr->data_lock); + struct rr_group *ans_grp = rr_group_find(svr->group, name); + if (ans_grp == NULL) { + pthread_mutex_unlock(&svr->data_lock); + return num_ans; + } + + // include all records? + if (type == RR_ANY) { + struct rr_list *n = ans_grp->rr; + for (; n; n = n->next) { + // exclude NSEC + if (n->e->type == RR_NSEC) + continue; + + num_ans += rr_list_append(rr_head, n->e); + } + } else { + // match record type + rr = rr_entry_find(ans_grp->rr, name, type); + if (rr) + num_ans += rr_list_append(rr_head, rr); + } + pthread_mutex_unlock(&svr->data_lock); + + return num_ans; +} + +// given a list of RRs, look up related records and add them +static void add_related_rr(struct mdnsd *svr, struct rr_list *list, struct mdns_pkt *reply) { + for (; list; list = list->next) { + struct rr_entry *ans = list->e; + + switch (ans->type) { + case RR_PTR: + // target host A, AAAA records + reply->num_add_rr += populate_answers(svr, &reply->rr_add, + (ans->data.PTR.name ? + ans->data.PTR.name : + ans->data.PTR.entry->name), + RR_ANY); + break; + + case RR_SRV: + // target host A, AAAA records + reply->num_add_rr += populate_answers(svr, &reply->rr_add, + ans->data.SRV.target, RR_ANY); + + // perhaps TXT records of the same name? + // if we use RR_ANY, we risk pulling in the same RR_SRV + reply->num_add_rr += populate_answers(svr, &reply->rr_add, + ans->name, RR_TXT); + break; + + case RR_A: + case RR_AAAA: + reply->num_add_rr += populate_answers(svr, &reply->rr_add, + ans->name, RR_NSEC); + break; + + default: + // nothing to add + break; + } + } +} + +// creates an announce packet given the type name PTR +static void announce_srv(struct mdnsd *svr, struct mdns_pkt *reply, uint8_t *name) { + mdns_init_reply(reply, 0); + + reply->num_ans_rr += populate_answers(svr, &reply->rr_ans, name, RR_PTR); + + // remember to add the services dns-sd PTR too + reply->num_ans_rr += populate_answers(svr, &reply->rr_ans, + SERVICES_DNS_SD_NLABEL, RR_PTR); + + // see if we can match additional records for answers + add_related_rr(svr, reply->rr_ans, reply); + + // additional records for additional records + add_related_rr(svr, reply->rr_add, reply); +} + +// processes the incoming MDNS packet +// returns >0 if processed, 0 otherwise +static int process_mdns_pkt(struct mdnsd *svr, struct mdns_pkt *pkt, struct mdns_pkt *reply) { + int i; + + assert(pkt != NULL); + + // is it standard query? + if ((pkt->flags & MDNS_FLAG_RESP) == 0 && + MDNS_FLAG_GET_OPCODE(pkt->flags) == 0) { + mdns_init_reply(reply, pkt->id); + + DEBUG_PRINTF("flags = %04x, qn = %d, ans = %d, add = %d\n", + pkt->flags, + pkt->num_qn, + pkt->num_ans_rr, + pkt->num_add_rr); + + // loop through questions + struct rr_list *qnl = pkt->rr_qn; + for (i = 0; i < pkt->num_qn; i++, qnl = qnl->next) { + struct rr_entry *qn = qnl->e; + char *namestr = nlabel_to_str(qn->name); + DEBUG_PRINTF("qn #%d: type 0x%02x %s - ", i, qn->type, namestr); + free(namestr); + + // check if it's a unicast query - we ignore those + if (qn->unicast_query) { + DEBUG_PRINTF("skipping unicast query\n"); + continue; + } + + // see if it is in the answers + if (rr_entry_find(pkt->rr_ans, qn->name, qn->type)) { + DEBUG_PRINTF("our record is already in their answers\n"); + continue; + } + + reply->num_ans_rr += populate_answers(svr, &reply->rr_ans, qn->name, qn->type); + + DEBUG_PRINTF("adding %d answers\n", reply->num_ans_rr); + } + + // see if we can match additional records for answers + add_related_rr(svr, reply->rr_ans, reply); + + // additional records for additional records + add_related_rr(svr, reply->rr_add, reply); + + DEBUG_PRINTF("\n"); + + return reply->num_ans_rr; + } + + return 0; +} + +// main loop to receive, process and send out MDNS replies +// also handles MDNS service announces +static void main_loop(struct mdnsd *svr) { + fd_set sockfd_set; + int max_fd = svr->sockfd; + + void *pkt_buffer = malloc(PACKET_SIZE); + + if (svr->notify_pipe[0] > max_fd) + max_fd = svr->notify_pipe[0]; + + struct mdns_pkt *mdns_reply = malloc(sizeof(struct mdns_pkt)); + memset(mdns_reply, 0, sizeof(struct mdns_pkt)); + + while (! svr->stop_flag) { + struct timeval tv = { + .tv_sec = 0, + .tv_usec = 0, + }; + + FD_ZERO(&sockfd_set); + FD_SET(svr->sockfd, &sockfd_set); + FD_SET(svr->notify_pipe[0], &sockfd_set); + select(max_fd + 1, &sockfd_set, NULL, NULL, &tv); + + if (FD_ISSET(svr->sockfd, &sockfd_set)) { + struct sockaddr_in fromaddr; + socklen_t sockaddr_size = sizeof(struct sockaddr_in); + + ssize_t recvsize = recvfrom(svr->sockfd, pkt_buffer, PACKET_SIZE, 0, + (struct sockaddr *) &fromaddr, &sockaddr_size); + if (recvsize < 0) { + log_message(LOG_ERR, "recv(): %m"); + } + + DEBUG_PRINTF("data from=%s size=%ld\n", inet_ntoa(fromaddr.sin_addr), (long) recvsize); + struct mdns_pkt *mdns = mdns_parse_pkt(pkt_buffer, recvsize); + if (mdns != NULL) { + if (process_mdns_pkt(svr, mdns, mdns_reply)) { + size_t replylen = mdns_encode_pkt(mdns_reply, pkt_buffer, PACKET_SIZE); + send_packet(svr->sockfd, pkt_buffer, replylen); + } + + mdns_pkt_destroy(mdns); + } + } + + // send out announces + while (1) { + struct rr_entry *ann_e = NULL; + + // extract from head of list + pthread_mutex_lock(&svr->data_lock); + if (svr->announce) + ann_e = rr_list_remove(&svr->announce, svr->announce->e); + pthread_mutex_unlock(&svr->data_lock); + + if (! ann_e) + break; + + char *namestr = nlabel_to_str(ann_e->name); + DEBUG_PRINTF("sending announce for %s\n", namestr); + free(namestr); + + announce_srv(svr, mdns_reply, ann_e->name); + + if (mdns_reply->num_ans_rr > 0) { + size_t replylen = mdns_encode_pkt(mdns_reply, pkt_buffer, PACKET_SIZE); + send_packet(svr->sockfd, pkt_buffer, replylen); + } + } + } + + // main thread terminating. send out "goodbye packets" for services + mdns_init_reply(mdns_reply, 0); + + pthread_mutex_lock(&svr->data_lock); + struct rr_list *svc_le = svr->services; + for (; svc_le; svc_le = svc_le->next) { + // set TTL to zero + svc_le->e->ttl = 0; + mdns_reply->num_ans_rr += rr_list_append(&mdns_reply->rr_ans, svc_le->e); + } + pthread_mutex_unlock(&svr->data_lock); + + // send out packet + if (mdns_reply->num_ans_rr > 0) { + size_t replylen = mdns_encode_pkt(mdns_reply, pkt_buffer, PACKET_SIZE); + send_packet(svr->sockfd, pkt_buffer, replylen); + } + + // destroy packet + mdns_init_reply(mdns_reply, 0); + free(mdns_reply); + + free(pkt_buffer); + + close(svr->sockfd); + + svr->stop_flag = 2; +} + +///////////////////////////////////////////////////// + + +void mdnsd_set_hostname(struct mdnsd *svr, const char *hostname, uint32_t ip) { + struct rr_entry *a_e = NULL, + *nsec_e = NULL; + + // currently can't be called twice + // dont ask me what happens if the IP changes + assert(svr->hostname == NULL); + + a_e = rr_create_a(create_nlabel(hostname), ip); + + nsec_e = rr_create(create_nlabel(hostname), RR_NSEC); + rr_set_nsec(nsec_e, RR_A); + + pthread_mutex_lock(&svr->data_lock); + svr->hostname = create_nlabel(hostname); + rr_group_add(&svr->group, a_e); + rr_group_add(&svr->group, nsec_e); + pthread_mutex_unlock(&svr->data_lock); +} + +struct mdns_service *mdnsd_register_svc(struct mdnsd *svr, const char *instance_name, + const char *type, uint16_t port, const char *hostname, const char *txt[]) { + struct rr_entry *txt_e = NULL, + *srv_e = NULL, + *ptr_e = NULL, + *bptr_e = NULL; + uint8_t *target; + uint8_t *inst_nlabel, *type_nlabel, *nlabel; + struct mdns_service *service = malloc(sizeof(struct mdns_service)); + memset(service, 0, sizeof(struct mdns_service)); + + // combine service name + type_nlabel = create_nlabel(type); + inst_nlabel = create_nlabel(instance_name); + nlabel = join_nlabel(inst_nlabel, type_nlabel); + + // create TXT record + if (txt && *txt) { + txt_e = rr_create(dup_nlabel(nlabel), RR_TXT); + rr_list_append(&service->entries, txt_e); + + // add TXTs + for (; *txt; txt++) + rr_add_txt(txt_e, *txt); + } + + // create SRV record + assert(hostname || svr->hostname); // either one as target + target = hostname ? + create_nlabel(hostname) : + dup_nlabel(svr->hostname); + + srv_e = rr_create_srv(dup_nlabel(nlabel), port, target); + rr_list_append(&service->entries, srv_e); + + // create PTR record for type + ptr_e = rr_create_ptr(type_nlabel, srv_e); + + // create services PTR record for type + // this enables the type to show up as a "service" + bptr_e = rr_create_ptr(dup_nlabel(SERVICES_DNS_SD_NLABEL), ptr_e); + + // modify lists here + pthread_mutex_lock(&svr->data_lock); + + if (txt_e) + rr_group_add(&svr->group, txt_e); + rr_group_add(&svr->group, srv_e); + rr_group_add(&svr->group, ptr_e); + rr_group_add(&svr->group, bptr_e); + + // append PTR entry to announce list + rr_list_append(&svr->announce, ptr_e); + rr_list_append(&svr->services, ptr_e); + + pthread_mutex_unlock(&svr->data_lock); + + // don't free type_nlabel - it's with the PTR record + free(nlabel); + free(inst_nlabel); + + // notify server + write(svr->notify_pipe[1], ".", 1); + + return service; +} + +void mdns_service_destroy(struct mdns_service *srv) { + assert(srv != NULL); + rr_list_destroy(srv->entries, 0); + free(srv); +} + +struct mdnsd *mdnsd_start() { + pthread_t tid; + pthread_attr_t attr; + + struct mdnsd *server = malloc(sizeof(struct mdnsd)); + memset(server, 0, sizeof(struct mdnsd)); + + if (pipe(server->notify_pipe) != 0) { + log_message(LOG_ERR, "pipe(): %m\n"); + free(server); + return NULL; + } + + server->sockfd = create_recv_sock(); + if (server->sockfd < 0) { + log_message(LOG_ERR, "unable to create recv socket"); + free(server); + return NULL; + } + + pthread_mutex_init(&server->data_lock, NULL); + + // init thread + pthread_attr_init(&attr); + pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); + + if (pthread_create(&tid, &attr, (void *(*)(void *)) main_loop, (void *) server) != 0) { + pthread_mutex_destroy(&server->data_lock); + free(server); + return NULL; + } + + return server; +} + +void mdnsd_stop(struct mdnsd *s) { + assert(s != NULL); + + struct timeval tv = { + .tv_sec = 0, + .tv_usec = 500 * 1000, + }; + + s->stop_flag = 1; + write(s->notify_pipe[1], ".", 1); + + while (s->stop_flag != 2) + select(0, NULL, NULL, NULL, &tv); + + close(s->notify_pipe[0]); + close(s->notify_pipe[1]); + + pthread_mutex_destroy(&s->data_lock); + rr_group_destroy(s->group); + rr_list_destroy(s->announce, 0); + rr_list_destroy(s->services, 0); + + if (s->hostname) + free(s->hostname); + + free(s); +} + diff --git a/mdnsd.h b/mdnsd.h new file mode 100644 index 0000000..2a6fb39 --- /dev/null +++ b/mdnsd.h @@ -0,0 +1,46 @@ +/* + * tinysvcmdns - a tiny MDNS implementation for publishing services + * Copyright (C) 2011 Darell Tan + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef __MDNSD_H__ +#define __MDNSD_H__ + +#include + +struct mdnsd; +struct mdns_service; + +// starts a MDNS responder instance +// returns NULL if unsuccessful +struct mdnsd *mdnsd_start(); + +// stops the given MDNS responder instance +void mdnsd_stop(struct mdnsd *s); + +// sets the hostname for the given MDNS responder instance +void mdnsd_set_hostname(struct mdnsd *svr, const char *hostname, uint32_t ip); + +// registers a service with the MDNS responder instance +struct mdns_service *mdnsd_register_svc(struct mdnsd *svr, const char *instance_name, + const char *type, uint16_t port, const char *hostname, const char *txt[]); + +// destroys the mdns_service struct returned by mdnsd_register_svc() +void mdns_service_destroy(struct mdns_service *srv); + + +#endif/*!__MDNSD_H__*/ diff --git a/testmdnsd.c b/testmdnsd.c new file mode 100644 index 0000000..0cce98e --- /dev/null +++ b/testmdnsd.c @@ -0,0 +1,56 @@ +/* + * tinysvcmdns - a tiny MDNS implementation for publishing services + * Copyright (C) 2011 Darell Tan + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include +#include +#include +#include "mdns.h" +#include "mdnsd.h" + +int main(int argc, char *argv[]) { + // create host entries + char *hostname = "some-random-host.local"; + + struct mdnsd *svr = mdnsd_start(); + if (svr == NULL) { + printf("mdnsd_start() error\n"); + return 1; + } + + printf("mdnsd_start OK. press ENTER to add hostname & service\n"); + getchar(); + + mdnsd_set_hostname(svr, hostname, inet_addr("192.168.0.29")); + + const char *txt[] = { + "path=/mywebsite", + NULL + }; + struct mdns_service *svc = mdnsd_register_svc(svr, "My Website", + "_http._tcp.local", 8080, NULL, txt); + mdns_service_destroy(svc); + + printf("added service and hostname. press ENTER to exit\n"); + getchar(); + + mdnsd_stop(svr); + + return 0; +} +