core/ngx_resolver.c源文件分析(3)
本章我们主要介绍一下ngx_resolver.c源文件，其主要是实现对nginx中涉及到的域名的解析。
1. 函数ngx_resolver_lookup_name()
static ngx_resolver_node_t *
ngx_resolver_lookup_name(ngx_resolver_t *r, ngx_str_t *name, uint32_t hash)
{
ngx_int_t rc;
ngx_rbtree_node_t *node, *sentinel;
ngx_resolver_node_t *rn;
node = r->name_rbtree.root;
sentinel = r->name_rbtree.sentinel;
while (node != sentinel) {
if (hash < node->key) {
node = node->left;
continue;
}
if (hash > node->key) {
node = node->right;
continue;
}
/* hash == node->key */
rn = ngx_resolver_node(node);
rc = ngx_memn2cmp(name->data, rn->name, name->len, rn->nlen);
if (rc == 0) {
return rn;
}
node = (rc < 0) ? node->left : node->right;
}
/* not found */
return NULL;
}此函数用于根据名称domain name从指定红黑树中查找节点。
2. 函数ngx_resolver_lookup_srv()
static ngx_resolver_node_t *
ngx_resolver_lookup_srv(ngx_resolver_t *r, ngx_str_t *name, uint32_t hash)
{
ngx_int_t rc;
ngx_rbtree_node_t *node, *sentinel;
ngx_resolver_node_t *rn;
node = r->srv_rbtree.root;
sentinel = r->srv_rbtree.sentinel;
while (node != sentinel) {
if (hash < node->key) {
node = node->left;
continue;
}
if (hash > node->key) {
node = node->right;
continue;
}
/* hash == node->key */
rn = ngx_resolver_node(node);
rc = ngx_memn2cmp(name->data, rn->name, name->len, rn->nlen);
if (rc == 0) {
return rn;
}
node = (rc < 0) ? node->left : node->right;
}
/* not found */
return NULL;
}此函数用于根据名称service name从指定红黑树中查找节点。
3. 函数ngx_resolver_lookup_addr()
static ngx_resolver_node_t *
ngx_resolver_lookup_addr(ngx_resolver_t *r, in_addr_t addr)
{
ngx_rbtree_node_t *node, *sentinel;
node = r->addr_rbtree.root;
sentinel = r->addr_rbtree.sentinel;
while (node != sentinel) {
if (addr < node->key) {
node = node->left;
continue;
}
if (addr > node->key) {
node = node->right;
continue;
}
/* addr == node->key */
return ngx_resolver_node(node);
}
/* not found */
return NULL;
}此函数用于根据addr从指定红黑树中查找节点。
4. 函数ngx_resolver_lookup_addr6()
#if (NGX_HAVE_INET6)
static ngx_resolver_node_t *
ngx_resolver_lookup_addr6(ngx_resolver_t *r, struct in6_addr *addr,
uint32_t hash)
{
ngx_int_t rc;
ngx_rbtree_node_t *node, *sentinel;
ngx_resolver_node_t *rn;
node = r->addr6_rbtree.root;
sentinel = r->addr6_rbtree.sentinel;
while (node != sentinel) {
if (hash < node->key) {
node = node->left;
continue;
}
if (hash > node->key) {
node = node->right;
continue;
}
/* hash == node->key */
rn = ngx_resolver_node(node);
rc = ngx_memcmp(addr, &rn->addr6, 16);
if (rc == 0) {
return rn;
}
node = (rc < 0) ? node->left : node->right;
}
/* not found */
return NULL;
}
#endif此函数适用于IPv6从指定红黑树中查找节点（当前我们并不支持NGX_HAVE_INET6宏定义)
5. 函数ngx_resolver_rbtree_insert_value()
static void
ngx_resolver_rbtree_insert_value(ngx_rbtree_node_t *temp,
ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel)
{
ngx_rbtree_node_t **p;
ngx_resolver_node_t *rn, *rn_temp;
for ( ;; ) {
if (node->key < temp->key) {
p = &temp->left;
} else if (node->key > temp->key) {
p = &temp->right;
} else { /* node->key == temp->key */
rn = ngx_resolver_node(node);
rn_temp = ngx_resolver_node(temp);
p = (ngx_memn2cmp(rn->name, rn_temp->name, rn->nlen, rn_temp->nlen)
< 0) ? &temp->left : &temp->right;
}
if (*p == sentinel) {
break;
}
temp = *p;
}
*p = node;
node->parent = temp;
node->left = sentinel;
node->right = sentinel;
ngx_rbt_red(node);
}此函数用于向以temp为根的红黑树中插入节点node。
6. 函数ngx_resolver_rbtree_insert_addr6_value()
#if (NGX_HAVE_INET6)
static void
ngx_resolver_rbtree_insert_addr6_value(ngx_rbtree_node_t *temp,
ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel)
{
ngx_rbtree_node_t **p;
ngx_resolver_node_t *rn, *rn_temp;
for ( ;; ) {
if (node->key < temp->key) {
p = &temp->left;
} else if (node->key > temp->key) {
p = &temp->right;
} else { /* node->key == temp->key */
rn = ngx_resolver_node(node);
rn_temp = ngx_resolver_node(temp);
p = (ngx_memcmp(&rn->addr6, &rn_temp->addr6, 16)
< 0) ? &temp->left : &temp->right;
}
if (*p == sentinel) {
break;
}
temp = *p;
}
*p = node;
node->parent = temp;
node->left = sentinel;
node->right = sentinel;
ngx_rbt_red(node);
}
#endif此函数用于向以temp为根的红黑树中插入节点node。（用于IPv6，当前我们并不支持此宏定义)
7. 函数ngx_resolver_create_name_query()
static ngx_int_t
ngx_resolver_create_name_query(ngx_resolver_t *r, ngx_resolver_node_t *rn,
ngx_str_t *name)
{
u_char *p, *s;
size_t len, nlen;
ngx_uint_t ident;
ngx_resolver_qs_t *qs;
ngx_resolver_hdr_t *query;
nlen = name->len ? (1 + name->len + 1) : 1;
len = sizeof(ngx_resolver_hdr_t) + nlen + sizeof(ngx_resolver_qs_t);
#if (NGX_HAVE_INET6)
p = ngx_resolver_alloc(r, r->ipv6 ? len * 2 : len);
#else
p = ngx_resolver_alloc(r, len);
#endif
if (p == NULL) {
return NGX_ERROR;
}
rn->qlen = (u_short) len;
rn->query = p;
#if (NGX_HAVE_INET6)
if (r->ipv6) {
rn->query6 = p + len;
}
#endif
query = (ngx_resolver_hdr_t *) p;
ident = ngx_random();
ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
"resolve: \"%V\" A %i", name, ident & 0xffff);
query->ident_hi = (u_char) ((ident >> 8) & 0xff);
query->ident_lo = (u_char) (ident & 0xff);
/* recursion query */
query->flags_hi = 1; query->flags_lo = 0;
/* one question */
query->nqs_hi = 0; query->nqs_lo = 1;
query->nan_hi = 0; query->nan_lo = 0;
query->nns_hi = 0; query->nns_lo = 0;
query->nar_hi = 0; query->nar_lo = 0;
p += sizeof(ngx_resolver_hdr_t) + nlen;
qs = (ngx_resolver_qs_t *) p;
/* query type */
qs->type_hi = 0; qs->type_lo = NGX_RESOLVE_A;
/* IN query class */
qs->class_hi = 0; qs->class_lo = 1;
/* convert "www.example.com" to "\3www\7example\3com\0" */
len = 0;
p--;
*p-- = '\0';
if (name->len == 0) {
return NGX_DECLINED;
}
for (s = name->data + name->len - 1; s >= name->data; s--) {
if (*s != '.') {
*p = *s;
len++;
} else {
if (len == 0 || len > 255) {
return NGX_DECLINED;
}
*p = (u_char) len;
len = 0;
}
p--;
}
if (len == 0 || len > 255) {
return NGX_DECLINED;
}
*p = (u_char) len;
#if (NGX_HAVE_INET6)
if (!r->ipv6) {
return NGX_OK;
}
p = rn->query6;
ngx_memcpy(p, rn->query, rn->qlen);
query = (ngx_resolver_hdr_t *) p;
ident = ngx_random();
ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
"resolve: \"%V\" AAAA %i", name, ident & 0xffff);
query->ident_hi = (u_char) ((ident >> 8) & 0xff);
query->ident_lo = (u_char) (ident & 0xff);
p += sizeof(ngx_resolver_hdr_t) + nlen;
qs = (ngx_resolver_qs_t *) p;
qs->type_lo = NGX_RESOLVE_AAAA;
#endif
return NGX_OK;
}此函数用于构造域名查询IP的报文。报文格式如下：
ngx_resolver_hdr_t domain name ngx_resolver_qs_t
注意构造查询报文时会设置：
rn->qlen = (u_short) len;
rn->query = p;即会保存查询报文及长度。
8. 函数ngx_resolver_create_srv_query()
static ngx_int_t
ngx_resolver_create_srv_query(ngx_resolver_t *r, ngx_resolver_node_t *rn,
ngx_str_t *name)
{
u_char *p, *s;
size_t len, nlen;
ngx_uint_t ident;
ngx_resolver_qs_t *qs;
ngx_resolver_hdr_t *query;
nlen = name->len ? (1 + name->len + 1) : 1;
len = sizeof(ngx_resolver_hdr_t) + nlen + sizeof(ngx_resolver_qs_t);
p = ngx_resolver_alloc(r, len);
if (p == NULL) {
return NGX_ERROR;
}
rn->qlen = (u_short) len;
rn->query = p;
query = (ngx_resolver_hdr_t *) p;
ident = ngx_random();
ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
"resolve: \"%V\" SRV %i", name, ident & 0xffff);
query->ident_hi = (u_char) ((ident >> 8) & 0xff);
query->ident_lo = (u_char) (ident & 0xff);
/* recursion query */
query->flags_hi = 1; query->flags_lo = 0;
/* one question */
query->nqs_hi = 0; query->nqs_lo = 1;
query->nan_hi = 0; query->nan_lo = 0;
query->nns_hi = 0; query->nns_lo = 0;
query->nar_hi = 0; query->nar_lo = 0;
p += sizeof(ngx_resolver_hdr_t) + nlen;
qs = (ngx_resolver_qs_t *) p;
/* query type */
qs->type_hi = 0; qs->type_lo = NGX_RESOLVE_SRV;
/* IN query class */
qs->class_hi = 0; qs->class_lo = 1;
/* converts "www.example.com" to "\3www\7example\3com\0" */
len = 0;
p--;
*p-- = '\0';
if (name->len == 0) {
return NGX_DECLINED;
}
for (s = name->data + name->len - 1; s >= name->data; s--) {
if (*s != '.') {
*p = *s;
len++;
} else {
if (len == 0 || len > 255) {
return NGX_DECLINED;
}
*p = (u_char) len;
len = 0;
}
p--;
}
if (len == 0 || len > 255) {
return NGX_DECLINED;
}
*p = (u_char) len;
return NGX_OK;
}此函数用于构造服务名查询IP的报文。报文格式如下：
ngx_resolver_hdr_t service name ngx_resolver_qs_t
注意构造查询报文时会设置：
rn->qlen = (u_short) len;
rn->query = p;即会保存查询报文及长度。
9. 函数ngx_resolver_create_addr_query()
static ngx_int_t
ngx_resolver_create_addr_query(ngx_resolver_t *r, ngx_resolver_node_t *rn,
ngx_resolver_addr_t *addr)
{
u_char *p, *d;
size_t len;
in_addr_t inaddr;
ngx_int_t n;
ngx_uint_t ident;
ngx_resolver_hdr_t *query;
struct sockaddr_in *sin;
#if (NGX_HAVE_INET6)
struct sockaddr_in6 *sin6;
#endif
switch (addr->sockaddr->sa_family) {
#if (NGX_HAVE_INET6)
case AF_INET6:
len = sizeof(ngx_resolver_hdr_t)
+ 64 + sizeof(".ip6.arpa.") - 1
+ sizeof(ngx_resolver_qs_t);
break;
#endif
default: /* AF_INET */
len = sizeof(ngx_resolver_hdr_t)
+ sizeof(".255.255.255.255.in-addr.arpa.") - 1
+ sizeof(ngx_resolver_qs_t);
}
p = ngx_resolver_alloc(r, len);
if (p == NULL) {
return NGX_ERROR;
}
rn->query = p;
query = (ngx_resolver_hdr_t *) p;
ident = ngx_random();
query->ident_hi = (u_char) ((ident >> 8) & 0xff);
query->ident_lo = (u_char) (ident & 0xff);
/* recursion query */
query->flags_hi = 1; query->flags_lo = 0;
/* one question */
query->nqs_hi = 0; query->nqs_lo = 1;
query->nan_hi = 0; query->nan_lo = 0;
query->nns_hi = 0; query->nns_lo = 0;
query->nar_hi = 0; query->nar_lo = 0;
p += sizeof(ngx_resolver_hdr_t);
switch (addr->sockaddr->sa_family) {
#if (NGX_HAVE_INET6)
case AF_INET6:
sin6 = (struct sockaddr_in6 *) addr->sockaddr;
for (n = 15; n >= 0; n--) {
p = ngx_sprintf(p, "\1%xd\1%xd",
sin6->sin6_addr.s6_addr[n] & 0xf,
(sin6->sin6_addr.s6_addr[n] >> 4) & 0xf);
}
p = ngx_cpymem(p, "\3ip6\4arpa\0", 10);
break;
#endif
default: /* AF_INET */
sin = (struct sockaddr_in *) addr->sockaddr;
inaddr = ntohl(sin->sin_addr.s_addr);
for (n = 0; n < 32; n += 8) {
d = ngx_sprintf(&p[1], "%ud", (inaddr >> n) & 0xff);
*p = (u_char) (d - &p[1]);
p = d;
}
p = ngx_cpymem(p, "\7in-addr\4arpa\0", 14);
}
/* query type "PTR", IN query class */
p = ngx_cpymem(p, "\0\14\0\1", 4);
rn->qlen = (u_short) (p - rn->query);
return NGX_OK;
}此函数用于构造向DNS服务器进行逆查询的报文，即查询addr地址处的域名。报文格式如下：
ngx_resolver_hdr_t 查询IP in-addr4arpa PTR
注意，我们在构造查询报文时还会将报文内容及长度保存在rn上。
10. 函数ngx_resolver_copy()
static ngx_int_t
ngx_resolver_copy(ngx_resolver_t *r, ngx_str_t *name, u_char *buf, u_char *src,
u_char *last)
{
char *err;
u_char *p, *dst;
ssize_t len;
ngx_uint_t i, n;
p = src;
len = -1;
/*
* compression pointers allow to create endless loop, so we set limit;
* 128 pointers should be enough to store 255-byte name
*/
for (i = 0; i < 128; i++) {
n = *p++;
if (n == 0) {
goto done;
}
if (n & 0xc0) {
n = ((n & 0x3f) << 8) + *p;
p = &buf[n];
} else {
len += 1 + n;
p = &p[n];
}
if (p >= last) {
err = "name is out of response";
goto invalid;
}
}
err = "compression pointers loop";
invalid:
ngx_log_error(r->log_level, r->log, 0, err);
return NGX_ERROR;
done:
if (name == NULL) {
return NGX_OK;
}
if (len == -1) {
ngx_str_null(name);
return NGX_OK;
}
dst = ngx_resolver_alloc(r, len);
if (dst == NULL) {
return NGX_ERROR;
}
name->data = dst;
n = *src++;
for ( ;; ) {
if (n & 0xc0) {
n = ((n & 0x3f) << 8) + *src;
src = &buf[n];
n = *src++;
} else {
ngx_strlow(dst, src, n);
dst += n;
src += n;
n = *src++;
if (n != 0) {
*dst++ = '.';
}
}
if (n == 0) {
name->len = dst - name->data;
return NGX_OK;
}
}
}此处主要是为了处理DNS返回的压缩指针。这里请参看[rfc1035 Message compression]。
11. 函数ngx_resolver_timeout_handler()
static void
ngx_resolver_timeout_handler(ngx_event_t *ev)
{
ngx_resolver_ctx_t *ctx;
ctx = ev->data;
ctx->state = NGX_RESOLVE_TIMEDOUT;
ctx->handler(ctx);
}此函数作为context在超时(context->timeout)之后的回调函数
12. 函数ngx_resolver_free_node()
static void
ngx_resolver_free_node(ngx_resolver_t *r, ngx_resolver_node_t *rn)
{
ngx_uint_t i;
/* lock alloc mutex */
if (rn->query) {
ngx_resolver_free_locked(r, rn->query);
}
if (rn->name) {
ngx_resolver_free_locked(r, rn->name);
}
if (rn->cnlen) {
ngx_resolver_free_locked(r, rn->u.cname);
}
if (rn->naddrs > 1 && rn->naddrs != (u_short) -1) {
ngx_resolver_free_locked(r, rn->u.addrs);
}
#if (NGX_HAVE_INET6)
if (rn->naddrs6 > 1 && rn->naddrs6 != (u_short) -1) {
ngx_resolver_free_locked(r, rn->u6.addrs6);
}
#endif
if (rn->nsrvs) {
for (i = 0; i < rn->nsrvs; i++) {
if (rn->u.srvs[i].name.data) {
ngx_resolver_free_locked(r, rn->u.srvs[i].name.data);
}
}
ngx_resolver_free_locked(r, rn->u.srvs);
}
ngx_resolver_free_locked(r, rn);
/* unlock alloc mutex */
}此函数用于释放一个ngx_resolver_node_t节点。删除如下：
1) query查询报文 2) name查询域名或服务名 3) 规范名称canonical name 4) 解析到的IP地址信息 5) SRV查询时的目标服务器信息
13. resolver相关的内存分配与释放
static void *
ngx_resolver_alloc(ngx_resolver_t *r, size_t size)
{
u_char *p;
/* lock alloc mutex */
p = ngx_alloc(size, r->log);
/* unlock alloc mutex */
return p;
}
static void *
ngx_resolver_calloc(ngx_resolver_t *r, size_t size)
{
u_char *p;
p = ngx_resolver_alloc(r, size);
if (p) {
ngx_memzero(p, size);
}
return p;
}
static void
ngx_resolver_free(ngx_resolver_t *r, void *p)
{
/* lock alloc mutex */
ngx_free(p);
/* unlock alloc mutex */
}
static void
ngx_resolver_free_locked(ngx_resolver_t *r, void *p)
{
ngx_free(p);
}14. 函数ngx_resolver_dup()
static void *
ngx_resolver_dup(ngx_resolver_t *r, void *src, size_t size)
{
void *dst;
dst = ngx_resolver_alloc(r, size);
if (dst == NULL) {
return dst;
}
ngx_memcpy(dst, src, size);
return dst;
}分配一块size大小的内存，并进行数据拷贝。
15. 函数ngx_resolver_export()
static ngx_resolver_addr_t *
ngx_resolver_export(ngx_resolver_t *r, ngx_resolver_node_t *rn,
ngx_uint_t rotate)
{
ngx_uint_t d, i, j, n;
u_char (*sockaddr)[NGX_SOCKADDRLEN];
in_addr_t *addr;
struct sockaddr_in *sin;
ngx_resolver_addr_t *dst;
#if (NGX_HAVE_INET6)
struct in6_addr *addr6;
struct sockaddr_in6 *sin6;
#endif
n = rn->naddrs;
#if (NGX_HAVE_INET6)
n += rn->naddrs6;
#endif
dst = ngx_resolver_calloc(r, n * sizeof(ngx_resolver_addr_t));
if (dst == NULL) {
return NULL;
}
sockaddr = ngx_resolver_calloc(r, n * NGX_SOCKADDRLEN);
if (sockaddr == NULL) {
ngx_resolver_free(r, dst);
return NULL;
}
i = 0;
d = rotate ? ngx_random() % n : 0;
if (rn->naddrs) {
j = rotate ? ngx_random() % rn->naddrs : 0;
addr = (rn->naddrs == 1) ? &rn->u.addr : rn->u.addrs;
do {
sin = (struct sockaddr_in *) sockaddr[d];
sin->sin_family = AF_INET;
sin->sin_addr.s_addr = addr[j++];
dst[d].sockaddr = (struct sockaddr *) sin;
dst[d++].socklen = sizeof(struct sockaddr_in);
if (d == n) {
d = 0;
}
if (j == rn->naddrs) {
j = 0;
}
} while (++i < rn->naddrs);
}
#if (NGX_HAVE_INET6)
if (rn->naddrs6) {
j = rotate ? ngx_random() % rn->naddrs6 : 0;
addr6 = (rn->naddrs6 == 1) ? &rn->u6.addr6 : rn->u6.addrs6;
do {
sin6 = (struct sockaddr_in6 *) sockaddr[d];
sin6->sin6_family = AF_INET6;
ngx_memcpy(sin6->sin6_addr.s6_addr, addr6[j++].s6_addr, 16);
dst[d].sockaddr = (struct sockaddr *) sin6;
dst[d++].socklen = sizeof(struct sockaddr_in6);
if (d == n) {
d = 0;
}
if (j == rn->naddrs6) {
j = 0;
}
} while (++i < n);
}
#endif
return dst;
}此函数用于导出ngx_resolver_node_t节点中的ip地址信息。参数rotate用于控制是否以一个随机的起始点导出数据。
16. 函数ngx_resolver_report_srv()
static void
ngx_resolver_report_srv(ngx_resolver_t *r, ngx_resolver_ctx_t *ctx)
{
ngx_uint_t naddrs, nsrvs, nw, i, j, k, l, m, n, w;
ngx_resolver_addr_t *addrs;
ngx_resolver_srv_name_t *srvs;
naddrs = 0;
for (i = 0; i < ctx->nsrvs; i++) {
naddrs += ctx->srvs[i].naddrs;
}
if (naddrs == 0) {
ctx->state = NGX_RESOLVE_NXDOMAIN;
ctx->valid = ngx_time() + (r->valid ? r->valid : 10);
ctx->handler(ctx);
return;
}
addrs = ngx_resolver_calloc(r, naddrs * sizeof(ngx_resolver_addr_t));
if (addrs == NULL) {
ctx->state = NGX_ERROR;
ctx->valid = ngx_time() + (r->valid ? r->valid : 10);
ctx->handler(ctx);
return;
}
srvs = ctx->srvs;
nsrvs = ctx->nsrvs;
i = 0;
n = 0;
do {
nw = 0;
for (j = i; j < nsrvs; j++) {
if (srvs[j].priority != srvs[i].priority) {
break;
}
nw += srvs[j].naddrs * srvs[j].weight;
}
if (nw == 0) {
goto next_srv;
}
w = ngx_random() % nw;
for (k = i; k < j; k++) {
if (w < srvs[k].naddrs * srvs[k].weight) {
break;
}
w -= srvs[k].naddrs * srvs[k].weight;
}
for (l = i; l < j; l++) {
for (m = 0; m < srvs[k].naddrs; m++) {
addrs[n].socklen = srvs[k].addrs[m].socklen;
addrs[n].sockaddr = srvs[k].addrs[m].sockaddr;
addrs[n].name = srvs[k].name;
addrs[n].priority = srvs[k].priority;
addrs[n].weight = srvs[k].weight;
n++;
}
if (++k == j) {
k = i;
}
}
next_srv:
i = j;
} while (i < ctx->nsrvs);
ctx->state = NGX_OK;
ctx->addrs = addrs;
ctx->naddrs = naddrs;
ctx->handler(ctx);
ngx_resolver_free(r, addrs);
}此函数用于按一定的顺序报告查询到的ip地址信息。
17. 函数ngx_resolver_strerror()
char *
ngx_resolver_strerror(ngx_int_t err)
{
static char *errors[] = {
"Format error", /* FORMERR */
"Server failure", /* SERVFAIL */
"Host not found", /* NXDOMAIN */
"Unimplemented", /* NOTIMP */
"Operation refused" /* REFUSED */
};
if (err > 0 && err < 6) {
return errors[err - 1];
}
if (err == NGX_RESOLVE_TIMEDOUT) {
return "Operation timed out";
}
return "Unknown error";
}打印指定错误码的error信息。
18. 函数ngx_resolver_log_error()
static u_char *
ngx_resolver_log_error(ngx_log_t *log, u_char *buf, size_t len)
{
u_char *p;
ngx_resolver_connection_t *rec;
p = buf;
if (log->action) {
p = ngx_snprintf(buf, len, " while %s", log->action);
len -= p - buf;
}
rec = log->data;
if (rec) {
p = ngx_snprintf(p, len, ", resolver: %V", &rec->server);
}
return p;
}用于将日志格式话到buf中。
19. 函数ngx_udp_connect()
ngx_int_t
ngx_udp_connect(ngx_resolver_connection_t *rec)
{
int rc;
ngx_int_t event;
ngx_event_t *rev, *wev;
ngx_socket_t s;
ngx_connection_t *c;
s = ngx_socket(rec->sockaddr->sa_family, SOCK_DGRAM, 0);
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, &rec->log, 0, "UDP socket %d", s);
if (s == (ngx_socket_t) -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_socket_n " failed");
return NGX_ERROR;
}
c = ngx_get_connection(s, &rec->log);
if (c == NULL) {
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_close_socket_n "failed");
}
return NGX_ERROR;
}
if (ngx_nonblocking(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_nonblocking_n " failed");
goto failed;
}
rev = c->read;
wev = c->write;
rev->log = &rec->log;
wev->log = &rec->log;
rec->udp = c;
c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, &rec->log, 0,
"connect to %V, fd:%d #%uA", &rec->server, s, c->number);
rc = connect(s, rec->sockaddr, rec->socklen);
/* TODO: iocp */
if (rc == -1) {
ngx_log_error(NGX_LOG_CRIT, &rec->log, ngx_socket_errno,
"connect() failed");
goto failed;
}
/* UDP sockets are always ready to write */
wev->ready = 1;
event = (ngx_event_flags & NGX_USE_CLEAR_EVENT) ?
/* kqueue, epoll */ NGX_CLEAR_EVENT:
/* select, poll, /dev/poll */ NGX_LEVEL_EVENT;
/* eventport event type has no meaning: oneshot only */
if (ngx_add_event(rev, NGX_READ_EVENT, event) != NGX_OK) {
goto failed;
}
return NGX_OK;
failed:
ngx_close_connection(c);
rec->udp = NULL;
return NGX_ERROR;
}此函数首先采用socket()方法构造一个fd，然后调用非阻塞的connect()连接到指定地址。注意： 针对UDP建立连接，那么后续在发送时就可以不用指定目标地址。
20 函数ngx_tcp_connect()
ngx_int_t
ngx_tcp_connect(ngx_resolver_connection_t *rec)
{
int rc;
ngx_int_t event;
ngx_err_t err;
ngx_uint_t level;
ngx_socket_t s;
ngx_event_t *rev, *wev;
ngx_connection_t *c;
s = ngx_socket(rec->sockaddr->sa_family, SOCK_STREAM, 0);
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, &rec->log, 0, "TCP socket %d", s);
if (s == (ngx_socket_t) -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_socket_n " failed");
return NGX_ERROR;
}
c = ngx_get_connection(s, &rec->log);
if (c == NULL) {
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_close_socket_n "failed");
}
return NGX_ERROR;
}
if (ngx_nonblocking(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_nonblocking_n " failed");
goto failed;
}
rev = c->read;
wev = c->write;
rev->log = &rec->log;
wev->log = &rec->log;
rec->tcp = c;
c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
if (ngx_add_conn) {
if (ngx_add_conn(c) == NGX_ERROR) {
goto failed;
}
}
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, &rec->log, 0,
"connect to %V, fd:%d #%uA", &rec->server, s, c->number);
rc = connect(s, rec->sockaddr, rec->socklen);
if (rc == -1) {
err = ngx_socket_errno;
if (err != NGX_EINPROGRESS
#if (NGX_WIN32)
/* Winsock returns WSAEWOULDBLOCK (NGX_EAGAIN) */
&& err != NGX_EAGAIN
#endif
)
{
if (err == NGX_ECONNREFUSED
#if (NGX_LINUX)
/*
* Linux returns EAGAIN instead of ECONNREFUSED
* for unix sockets if listen queue is full
*/
|| err == NGX_EAGAIN
#endif
|| err == NGX_ECONNRESET
|| err == NGX_ENETDOWN
|| err == NGX_ENETUNREACH
|| err == NGX_EHOSTDOWN
|| err == NGX_EHOSTUNREACH)
{
level = NGX_LOG_ERR;
} else {
level = NGX_LOG_CRIT;
}
ngx_log_error(level, c->log, err, "connect() to %V failed",
&rec->server);
ngx_close_connection(c);
rec->tcp = NULL;
return NGX_ERROR;
}
}
if (ngx_add_conn) {
if (rc == -1) {
/* NGX_EINPROGRESS */
return NGX_AGAIN;
}
ngx_log_debug0(NGX_LOG_DEBUG_EVENT, &rec->log, 0, "connected");
wev->ready = 1;
return NGX_OK;
}
if (ngx_event_flags & NGX_USE_IOCP_EVENT) {
ngx_log_debug1(NGX_LOG_DEBUG_EVENT, &rec->log, ngx_socket_errno,
"connect(): %d", rc);
if (ngx_blocking(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, &rec->log, ngx_socket_errno,
ngx_blocking_n " failed");
goto failed;
}
/*
* FreeBSD's aio allows to post an operation on non-connected socket.
* NT does not support it.
*
* TODO: check in Win32, etc. As workaround we can use NGX_ONESHOT_EVENT
*/
rev->ready = 1;
wev->ready = 1;
return NGX_OK;
}
if (ngx_event_flags & NGX_USE_CLEAR_EVENT) {
/* kqueue */
event = NGX_CLEAR_EVENT;
} else {
/* select, poll, /dev/poll */
event = NGX_LEVEL_EVENT;
}
if (ngx_add_event(rev, NGX_READ_EVENT, event) != NGX_OK) {
goto failed;
}
if (rc == -1) {
/* NGX_EINPROGRESS */
if (ngx_add_event(wev, NGX_WRITE_EVENT, event) != NGX_OK) {
goto failed;
}
return NGX_AGAIN;
}
ngx_log_debug0(NGX_LOG_DEBUG_EVENT, &rec->log, 0, "connected");
wev->ready = 1;
return NGX_OK;
failed:
ngx_close_connection(c);
rec->tcp = NULL;
return NGX_ERROR;
}此函数用于建立一个tcp连接。下面我们简要分析一下建立流程：
ngx_int_t
ngx_tcp_connect(ngx_resolver_connection_t *rec)
{
//1) 调用socket()方法建立文件句柄fd
//2) 从全局ngx_cycle中获取一个空闲的connection对象
//3) 设置socket为非阻塞方式
//4) 将连接的使用次数加1
c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
//5) 调用connect()函数连接到服务器
rc = connect(s, rec->sockaddr, rec->socklen);
if (rc == -1)
{
//5.1 如果errno值为NGX_EINPROGRESS，表示当前socket为非阻塞模式并且不能马上返回连接
}
//6) 处理ready情况, 表明当前socket正处于连接中
if (ngx_add_conn) {
if (rc == -1) {
/* NGX_EINPROGRESS */
return NGX_AGAIN;
}
ngx_log_debug0(NGX_LOG_DEBUG_EVENT, &rec->log, 0, "connected");
wev->ready = 1;
return NGX_OK;
}
//7) 在socket上监听相应的可读、可写事件
}21. 函数ngx_resolver_cmp_srvs()
static ngx_int_t
ngx_resolver_cmp_srvs(const void *one, const void *two)
{
ngx_int_t p1, p2;
ngx_resolver_srv_t *first, *second;
first = (ngx_resolver_srv_t *) one;
second = (ngx_resolver_srv_t *) two;
p1 = first->priority;
p2 = second->priority;
return p1 - p2;
}根据priority来比较两个ngx_resolver_srv_t类型对象的大小。
[参看]
