106 lines
3.1 KiB
Go
106 lines
3.1 KiB
Go
package send
|
||
|
||
import (
|
||
stdcontext "context"
|
||
"errors"
|
||
"fmt"
|
||
"net"
|
||
"net/textproto"
|
||
"sort"
|
||
"strings"
|
||
"time"
|
||
|
||
"git.pcux.cn/xuans/Smail/utils/smtp"
|
||
)
|
||
|
||
var errNullMX = errors.New("收件域名声明不接收邮件")
|
||
|
||
type mxLookup func(stdcontext.Context, string) ([]*net.MX, error)
|
||
|
||
func resolveMX(domain string, lookup mxLookup) ([]string, error) {
|
||
return resolveMXContext(stdcontext.Background(), domain, lookup)
|
||
}
|
||
|
||
func resolveMXContext(parent stdcontext.Context, domain string, lookup mxLookup) ([]string, error) {
|
||
ctx, cancel := stdcontext.WithTimeout(parent, 10*time.Second)
|
||
defer cancel()
|
||
records, err := lookup(ctx, domain)
|
||
if err != nil {
|
||
var dnsErr *net.DNSError
|
||
if !errors.As(err, &dnsErr) || !dnsErr.IsNotFound || dnsErr.IsTemporary || dnsErr.IsTimeout {
|
||
return nil, fmt.Errorf("查询收件域名 MX 失败: %w", err)
|
||
}
|
||
// 无 MX 时使用域名自身的地址记录，不猜测 smtp 子域名。
|
||
return []string{domain}, nil
|
||
}
|
||
if len(records) == 0 {
|
||
return []string{domain}, nil
|
||
}
|
||
records = append([]*net.MX(nil), records...)
|
||
for _, record := range records {
|
||
if record == nil || record.Host == "" {
|
||
return nil, errors.New("收件域名 MX 记录无效")
|
||
}
|
||
if record.Host == "." {
|
||
return nil, errNullMX
|
||
}
|
||
}
|
||
sort.SliceStable(records, func(i, j int) bool { return records[i].Pref < records[j].Pref })
|
||
hosts := make([]string, 0, len(records))
|
||
seen := make(map[string]bool)
|
||
for _, record := range records {
|
||
host := strings.ToLower(strings.TrimSuffix(record.Host, "."))
|
||
if !seen[host] {
|
||
hosts = append(hosts, host)
|
||
seen[host] = true
|
||
}
|
||
}
|
||
return hosts, nil
|
||
}
|
||
|
||
func stopFallback(err error) bool {
|
||
return smtp.IsDeliveryUncertain(err) || isCertificateVerificationError(err) || isPermanentSMTPResponse(err) || errors.Is(err, smtp.ErrUnsafeRemoteAddress)
|
||
}
|
||
|
||
// deliverMX 只在确认本次未接收时切换安全通道，DATA 不确定结果不进入下一条路由。
|
||
func deliverMX(hosts []string, attempt func(host, port string) error) error {
|
||
return deliverMXContext(stdcontext.Background(), hosts, attempt)
|
||
}
|
||
|
||
func deliverMXContext(ctx stdcontext.Context, hosts []string, attempt func(host, port string) error) error {
|
||
var lastErr error
|
||
for _, host := range hosts {
|
||
// 标准投递端口不可达时优先尝试隐式 TLS，避免先等待不提供欢迎响应的提交端口。
|
||
for _, port := range []string{"25", "465", "587"} {
|
||
if err := ctx.Err(); err != nil {
|
||
return err
|
||
}
|
||
lastErr = attempt(host, port)
|
||
if lastErr == nil || stopFallback(lastErr) {
|
||
return lastErr
|
||
}
|
||
}
|
||
}
|
||
if lastErr == nil {
|
||
lastErr = errors.New("收件域名没有可用邮件服务器")
|
||
}
|
||
return lastErr
|
||
}
|
||
|
||
// Retryable 仅允许有明确临时失败语义的结果进入持久队列重试。
|
||
func Retryable(err error) bool {
|
||
if err == nil || stopFallback(err) {
|
||
return false
|
||
}
|
||
var response *textproto.Error
|
||
if errors.As(err, &response) {
|
||
return response.Code >= 400 && response.Code <= 499
|
||
}
|
||
var dnsErr *net.DNSError
|
||
if errors.As(err, &dnsErr) {
|
||
return dnsErr.IsTimeout || dnsErr.IsTemporary
|
||
}
|
||
var networkErr net.Error
|
||
return errors.As(err, &networkErr)
|
||
}
|