static int smtp_reuse_session(SMTP_STATE *state, int lookup_mx,
const char *domain, unsigned port,
DNS_RR **addr_list, int domain_best_pref)
{
int session_count = 0;
DNS_RR *addr;
DNS_RR *next;
MAI_HOSTADDR_STR hostaddr;
SMTP_SESSION *session;
/*
* First, search the cache by logical destination. We truncate the server
* address list when all the sessions for this destination are used up,
* to reduce the number of variables that need to be checked later.
*
* Note: lookup by logical destination restores the "best MX" bit.
*/
if (*addr_list && SMTP_RCPT_LEFT(state) > 0
&& (session = smtp_reuse_domain(state, lookup_mx, domain, port)) != 0) {
session_count = 1;
smtp_update_addr_list(addr_list, session->addr, session_count);
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& *addr_list == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
smtp_xfer(state);
smtp_cleanup_session(state);
}
/*
* Second, search the cache by primary MX address. Again, we use address
* list truncation so that we have to check fewer variables later.
*
* XXX This loop is safe because smtp_update_addr_list() either truncates
* the list to zero length, or removes at most one list element.
*/
for (addr = *addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
if (addr->pref != domain_best_pref)
break;
next = addr->next;
if (dns_rr_to_pa(addr, &hostaddr) != 0
&& (session = smtp_reuse_addr(state, hostaddr.buf, port)) != 0) {
session->features |= SMTP_FEATURE_BEST_MX;
session_count += 1;
smtp_update_addr_list(addr_list, session->addr, session_count);
if (*addr_list == 0)
next = 0;
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& next == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
smtp_xfer(state);
smtp_cleanup_session(state);
}
}
return (session_count);
}
static void smtp_connect_inet(SMTP_STATE *state, const char *nexthop,
char *def_service)
{
DELIVER_REQUEST *request = state->request;
SMTP_ITERATOR *iter = state->iterator;
ARGV *sites;
char *dest;
char **cpp;
int non_fallback_sites;
int retry_plain = 0;
DSN_BUF *why = state->why;
/*
* For sanity, require that at least one of INET or INET6 is enabled.
* Otherwise, we can't look up interface information, and we can't
* convert names or addresses.
*/
if (inet_proto_info()->ai_family_list[0] == 0) {
dsb_simple(why, "4.4.4", "all network protocols are disabled");
return;
}
/*
* Future proofing: do a null destination sanity check in case we allow
* the primary destination to be a list (it could be just separators).
*/
sites = argv_alloc(1);
argv_add(sites, nexthop, (char *) 0);
if (sites->argc == 0)
msg_panic("null destination: \"%s\"", nexthop);
non_fallback_sites = sites->argc;
argv_split_append(sites, var_fallback_relay, CHARS_COMMA_SP);
/*
* Don't give up after a hard host lookup error until we have tried the
* fallback relay servers.
*
* Don't bounce mail after a host lookup problem with a relayhost or with a
* fallback relay.
*
* Don't give up after a qualifying soft error until we have tried all
* qualifying backup mail servers.
*
* All this means that error handling and error reporting depends on whether
* the error qualifies for trying to deliver to a backup mail server, or
* whether we're looking up a relayhost or fallback relay. The challenge
* then is to build this into the pre-existing SMTP client without
* getting lost in the complexity.
*/
#define IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites) \
(*(cpp) && (cpp) >= (sites)->argv + (non_fallback_sites))
for (cpp = sites->argv, (state->misc_flags |= SMTP_MISC_FLAG_FIRST_NEXTHOP);
SMTP_RCPT_LEFT(state) > 0 && (dest = *cpp) != 0;
cpp++, (state->misc_flags &= ~SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
char *dest_buf;
char *domain;
unsigned port;
DNS_RR *addr_list;
DNS_RR *addr;
DNS_RR *next;
int addr_count;
int sess_count;
SMTP_SESSION *session;
int lookup_mx;
unsigned domain_best_pref;
MAI_HOSTADDR_STR hostaddr;
if (cpp[1] == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
/*
* Parse the destination. If no TCP port is specified, use the port
* that is reserved for the protocol (SMTP or LMTP).
*/
dest_buf = smtp_parse_destination(dest, def_service, &domain, &port);
if (var_helpful_warnings && var_smtp_tls_wrappermode == 0
&& ntohs(port) == 465) {
msg_info("SMTPS wrappermode (TCP port 465) requires setting "
"\"%s = yes\", and \"%s = encrypt\" (or stronger)",
VAR_LMTP_SMTP(TLS_WRAPPER), VAR_LMTP_SMTP(TLS_LEVEL));
}
#define NO_HOST "" /* safety */
#define NO_ADDR "" /* safety */
SMTP_ITER_INIT(iter, dest, NO_HOST, NO_ADDR, port, state);
/*
* Resolve an SMTP or LMTP server. In the case of SMTP, skip mail
* exchanger lookups when a quoted host is specified or when DNS
* lookups are disabled.
*/
if (msg_verbose)
msg_info("connecting to %s port %d", domain, ntohs(port));
if (smtp_mode) {
if (ntohs(port) == IPPORT_SMTP)
state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT;
else
state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT;
lookup_mx = (smtp_dns_support != SMTP_DNS_DISABLED && *dest != '[');
} else
lookup_mx = 0;
if (!lookup_mx) {
addr_list = smtp_host_addr(domain, state->misc_flags, why);
/* XXX We could be an MX host for this destination... */
} else {
int i_am_mx = 0;
addr_list = smtp_domain_addr(domain, &iter->mx, state->misc_flags,
why, &i_am_mx);
/* If we're MX host, don't connect to non-MX backups. */
if (i_am_mx)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
}
/*
* Don't try fall-back hosts if mail loops to myself. That would just
* make the problem worse.
*/
if (addr_list == 0 && SMTP_HAS_LOOP_DSN(why))
state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
/*
* No early loop exit or we have a memory leak with dest_buf.
*/
if (addr_list)
domain_best_pref = addr_list->pref;
/*
* When session caching is enabled, store the first good session for
* this delivery request under the next-hop destination name. All
* good sessions will be stored under their specific server IP
* address.
*
* XXX smtp_session_cache_destinations specifies domain names without
* :port, because : is already used for maptype:mapname. Because of
* this limitation we use the bare domain without the optional [] or
* non-default TCP port.
*
* Opportunistic (a.k.a. on-demand) session caching on request by the
* queue manager. This is turned temporarily when a destination has a
* high volume of mail in the active queue. When the surge reaches
* its end, the queue manager requests that connections be retrieved
* but not stored.
*/
if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
smtp_cache_policy(state, domain);
if (state->misc_flags & SMTP_MISC_FLAG_CONN_CACHE_MASK)
SET_NEXTHOP_STATE(state, dest);
}
/*
* Delete visited cached hosts from the address list.
*
* Optionally search the connection cache by domain name or by primary
* MX address before we try to create new connections.
*
* Enforce the MX session and MX address counts per next-hop or
* fall-back destination. smtp_reuse_session() will truncate the
* address list when either limit is reached.
*/
if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD)) {
if (state->cache_used->used > 0)
smtp_scrub_addr_list(state->cache_used, &addr_list);
sess_count = addr_count =
smtp_reuse_session(state, &addr_list, domain_best_pref);
} else
sess_count = addr_count = 0;
/*
* Connect to an SMTP server: create primary MX connections, and
* reuse or create backup MX connections.
*
* At the start of an SMTP session, all recipients are unmarked. In the
* course of an SMTP session, recipients are marked as KEEP (deliver
* to alternate mail server) or DROP (remove from recipient list). At
* the end of an SMTP session, weed out the recipient list. Unmark
* any left-over recipients and try to deliver them to a backup mail
* server.
*
* Cache the first good session under the next-hop destination name.
* Cache all good sessions under their physical endpoint.
*
* Don't query the session cache for primary MX hosts. We already did
* that in smtp_reuse_session(), and if any were found in the cache,
* they were already deleted from the address list.
*
* Currently, we use smtp_reuse_addr() only for SASL-unauthenticated
* connections. Furthermore, we rely on smtp_reuse_addr() to look up
* an existing SASL-unauthenticated connection only when a new
* connection would be guaranteed not to require SASL authentication.
*
* In addition, we rely on smtp_reuse_addr() to look up an existing
* plaintext connection only when a new connection would be
* guaranteed not to use TLS.
*/
for (addr = addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
next = addr->next;
if (++addr_count == var_smtp_mxaddr_limit)
next = 0;
if (dns_rr_to_pa(addr, &hostaddr) == 0) {
msg_warn("cannot convert type %s record to printable address",
dns_strtype(addr->type));
/* XXX Assume there is no code at the end of this loop. */
continue;
}
vstring_strcpy(iter->addr, hostaddr.buf);
vstring_strcpy(iter->host, SMTP_HNAME(addr));
iter->rr = addr;
#ifdef USE_TLS
if (!smtp_tls_policy_cache_query(why, state->tls, iter)) {
msg_warn("TLS policy lookup for %s/%s: %s",
STR(iter->dest), STR(iter->host), STR(why->reason));
continue;
/* XXX Assume there is no code at the end of this loop. */
}
if (var_smtp_tls_wrappermode
&& state->tls->level < TLS_LEV_ENCRYPT) {
msg_warn("%s requires \"%s = encrypt\" (or stronger)",
VAR_LMTP_SMTP(TLS_WRAPPER), VAR_LMTP_SMTP(TLS_LEVEL));
continue;
/* XXX Assume there is no code at the end of this loop. */
}
/* Disable TLS when retrying after a handshake failure */
if (retry_plain) {
state->tls->level = TLS_LEV_NONE;
retry_plain = 0;
}
#endif
if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
|| addr->pref == domain_best_pref
|| !(session = smtp_reuse_addr(state,
SMTP_KEY_MASK_SCACHE_ENDP_LABEL)))
session = smtp_connect_addr(iter, why, state->misc_flags);
if ((state->session = session) != 0) {
session->state = state;
#ifdef USE_TLS
session->tls_nexthop = domain;
#endif
if (addr->pref == domain_best_pref)
session->features |= SMTP_FEATURE_BEST_MX;
/* Don't count handshake errors towards the session limit. */
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& next == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
&& smtp_helo(state) != 0) {
#ifdef USE_TLS
/*
* When an opportunistic TLS handshake fails, try the
* same address again, with TLS disabled. See also the
* RETRY_AS_PLAINTEXT macro.
*/
if ((retry_plain = session->tls_retry_plain) != 0) {
--addr_count;
next = addr;
}
#endif
/*
* When a TLS handshake fails, the stream is marked
* "dead" to avoid further I/O over a broken channel.
*/
if (!THIS_SESSION_IS_FORBIDDEN
&& vstream_ferror(session->stream) == 0
&& vstream_feof(session->stream) == 0)
smtp_quit(state);
} else {
/* Do count delivery errors towards the session limit. */
if (++sess_count == var_smtp_mxsess_limit)
next = 0;
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& next == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
smtp_xfer(state);
#ifdef USE_TLS
/*
* When opportunistic TLS fails after the STARTTLS
* handshake, try the same address again, with TLS
* disabled. See also the RETRY_AS_PLAINTEXT macro.
*/
if ((retry_plain = session->tls_retry_plain) != 0) {
--sess_count;
--addr_count;
next = addr;
}
#endif
}
smtp_cleanup_session(state);
} else {
/* The reason already includes the IP address and TCP port. */
msg_info("%s", STR(why->reason));
}
/* XXX Code above assumes there is no code at this loop ending. */
}
dns_rr_free(addr_list);
if (iter->mx) {
dns_rr_free(iter->mx);
iter->mx = 0; /* Just in case */
}
myfree(dest_buf);
if (state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
break;
}
/*
* We still need to deliver, bounce or defer some left-over recipients:
* either mail loops or some backup mail server was unavailable.
*/
if (SMTP_RCPT_LEFT(state) > 0) {
/*
* In case of a "no error" indication we make up an excuse: we did
* find the host address, but we did not attempt to connect to it.
* This can happen when the fall-back relay was already tried via a
* cached connection, so that the address list scrubber left behind
* an empty list.
*/
if (!SMTP_HAS_DSN(why)) {
dsb_simple(why, "4.3.0",
"server unavailable or unable to receive mail");
}
/*
* Pay attention to what could be configuration problems, and pretend
* that these are recoverable rather than bouncing the mail.
*/
else if (!SMTP_HAS_SOFT_DSN(why)) {
/*
* The fall-back destination did not resolve as expected, or it
* is refusing to talk to us, or mail for it loops back to us.
*/
if (IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites)) {
msg_warn("%s configuration problem", VAR_SMTP_FALLBACK);
vstring_strcpy(why->status, "4.3.5");
/* XXX Keep the diagnostic code and MTA. */
}
/*
* The next-hop relayhost did not resolve as expected, or it is
* refusing to talk to us, or mail for it loops back to us.
*
* XXX There is no equivalent safety net for mis-configured
* sender-dependent relay hosts. The trivial-rewrite resolver
* would have to flag the result, and the queue manager would
* have to provide that information to delivery agents.
*/
else if (smtp_mode && strcmp(sites->argv[0], var_relayhost) == 0) {
msg_warn("%s configuration problem", VAR_RELAYHOST);
vstring_strcpy(why->status, "4.3.5");
/* XXX Keep the diagnostic code and MTA. */
}
/*
* Mail for the next-hop destination loops back to myself. Pass
* the mail to the best_mx_transport or bounce it.
*/
else if (smtp_mode && SMTP_HAS_LOOP_DSN(why) && *var_bestmx_transp) {
dsb_reset(why); /* XXX */
state->status = deliver_pass_all(MAIL_CLASS_PRIVATE,
var_bestmx_transp,
request);
SMTP_RCPT_LEFT(state) = 0; /* XXX */
}
}
}
/*
* Cleanup.
*/
if (HAVE_NEXTHOP_STATE(state))
FREE_NEXTHOP_STATE(state);
argv_free(sites);
}
static int smtp_reuse_session(SMTP_STATE *state, DNS_RR **addr_list,
int domain_best_pref)
{
int session_count = 0;
DNS_RR *addr;
DNS_RR *next;
MAI_HOSTADDR_STR hostaddr;
SMTP_SESSION *session;
SMTP_ITERATOR *iter = state->iterator;
DSN_BUF *why = state->why;
/*
* First, search the cache by request nexthop. We truncate the server
* address list when all the sessions for this destination are used up,
* to reduce the number of variables that need to be checked later.
*
* Note: lookup by logical destination restores the "best MX" bit.
*
* smtp_reuse_nexthop() clobbers the iterators's "dest" attribute. We save
* and restore it here, so that subsequent connections will use the
* proper nexthop information.
*
* We request a dummy "TLS disabled" policy for connection-cache lookup by
* request nexthop only. If we find a saved connection, then we know that
* plaintext was permitted, because we never save a connection after
* turning on TLS.
*/
#ifdef USE_TLS
smtp_tls_policy_dummy(state->tls);
#endif
SMTP_ITER_SAVE_DEST(state->iterator);
if (*addr_list && SMTP_RCPT_LEFT(state) > 0
&& HAVE_NEXTHOP_STATE(state)
&& (session = smtp_reuse_nexthop(state, SMTP_KEY_MASK_SCACHE_DEST_LABEL)) != 0) {
session_count = 1;
smtp_update_addr_list(addr_list, STR(iter->addr), session_count);
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& *addr_list == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
smtp_xfer(state);
smtp_cleanup_session(state);
}
SMTP_ITER_RESTORE_DEST(state->iterator);
/*
* Second, search the cache by primary MX address. Again, we use address
* list truncation so that we have to check fewer variables later.
*
* XXX This loop is safe because smtp_update_addr_list() either truncates
* the list to zero length, or removes at most one list element.
*
* Currently, we use smtp_reuse_addr() only for SASL-unauthenticated
* connections. Furthermore, we rely on smtp_reuse_addr() to look up an
* existing SASL-unauthenticated connection only when a new connection
* would be guaranteed not to require SASL authentication.
*
* In addition, we rely on smtp_reuse_addr() to look up an existing
* plaintext connection only when a new connection would be guaranteed
* not to use TLS.
*
* For more precise control over reuse, the iterator should look up SASL and
* TLS policy as it evaluates mail exchangers in order, instead of
* relying on duplicate lookup request code in smtp_reuse(3) and
* smtp_session(3).
*/
for (addr = *addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
if (addr->pref != domain_best_pref)
break;
next = addr->next;
if (dns_rr_to_pa(addr, &hostaddr) == 0) {
msg_warn("cannot convert type %s record to printable address",
dns_strtype(addr->type));
/* XXX Assume there is no code at the end of this loop. */
continue;
}
vstring_strcpy(iter->addr, hostaddr.buf);
vstring_strcpy(iter->host, SMTP_HNAME(addr));
iter->rr = addr;
#ifdef USE_TLS
if (!smtp_tls_policy_cache_query(why, state->tls, iter)) {
msg_warn("TLS policy lookup error for %s/%s: %s",
STR(iter->dest), STR(iter->host), STR(why->reason));
continue;
/* XXX Assume there is no code at the end of this loop. */
}
#endif
if ((session = smtp_reuse_addr(state,
SMTP_KEY_MASK_SCACHE_ENDP_LABEL)) != 0) {
session->features |= SMTP_FEATURE_BEST_MX;
session_count += 1;
smtp_update_addr_list(addr_list, STR(iter->addr), session_count);
if (*addr_list == 0)
next = 0;
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& next == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
smtp_xfer(state);
smtp_cleanup_session(state);
}
}
return (session_count);
}
static void smtp_connect_local(SMTP_STATE *state, const char *path)
{
const char *myname = "smtp_connect_local";
SMTP_ITERATOR *iter = state->iterator;
SMTP_SESSION *session;
DSN_BUF *why = state->why;
/*
* Do not silently ignore an unused setting.
*/
if (*var_fallback_relay)
msg_warn("ignoring \"%s = %s\" setting for non-TCP connections",
VAR_LMTP_FALLBACK, var_fallback_relay);
/*
* It's too painful to weave this code into the SMTP connection
* management routine.
*
* Connection cache management is based on the UNIX-domain pathname, without
* the "unix:" prefix.
*/
smtp_cache_policy(state, path);
/*
* Here we ensure that the iter->addr member refers to a copy of the
* UNIX-domain pathname, so that smtp_save_session() will cache the
* connection using the pathname as the physical endpoint name.
*
* We set dest=path for backwards compatibility.
*/
#define NO_PORT 0
SMTP_ITER_INIT(iter, path, var_myhostname, path, NO_PORT, state);
/*
* Opportunistic TLS for unix domain sockets does not make much sense,
* since the channel is private, mere encryption without authentication
* is just wasted cycles and opportunity for breakage. Since we are not
* willing to retry after TLS handshake failures here, we downgrade "may"
* no "none". Nothing is lost, and much waste is avoided.
*
* We don't know who is authenticating whom, so if a client cert is
* available, "encrypt" may be a sensible policy. Otherwise, we also
* downgrade "encrypt" to "none", this time just to avoid waste.
*
* We use smtp_reuse_nexthop() instead of smtp_reuse_addr(), so that we can
* reuse a SASL-authenticated connection (however unlikely this scenario
* may be). The smtp_reuse_addr() interface currently supports only reuse
* of SASL-unauthenticated connections.
*/
#ifdef USE_TLS
if (!smtp_tls_policy_cache_query(why, state->tls, iter)) {
msg_warn("TLS policy lookup error for %s/%s: %s",
STR(iter->host), STR(iter->addr), STR(why->reason));
return;
}
#endif
if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
|| (session = smtp_reuse_nexthop(state,
SMTP_KEY_MASK_SCACHE_DEST_LABEL)) == 0)
session = smtp_connect_unix(iter, why, state->misc_flags);
if ((state->session = session) != 0) {
session->state = state;
#ifdef USE_TLS
session->tls_nexthop = var_myhostname; /* for TLS_LEV_SECURE */
if (state->tls->level == TLS_LEV_MAY) {
msg_warn("%s: opportunistic TLS encryption is not appropriate "
"for unix-domain destinations.", myname);
state->tls->level = TLS_LEV_NONE;
}
#endif
/* All delivery errors bounce or defer. */
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
/*
* When a TLS handshake fails, the stream is marked "dead" to avoid
* further I/O over a broken channel.
*/
if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
&& smtp_helo(state) != 0) {
if (!THIS_SESSION_IS_FORBIDDEN
&& vstream_ferror(session->stream) == 0
&& vstream_feof(session->stream) == 0)
smtp_quit(state);
} else {
smtp_xfer(state);
}
/*
* With opportunistic TLS disabled we don't expect to be asked to
* retry connections without TLS, and so we expect the final server
* flag to stay on.
*/
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_SERVER) == 0)
msg_panic("%s: unix-domain destination not final!", myname);
smtp_cleanup_session(state);
}
}
static void smtp_connect_remote(SMTP_STATE *state, const char *nexthop,
char *def_service)
{
DELIVER_REQUEST *request = state->request;
ARGV *sites;
char *dest;
char **cpp;
int non_fallback_sites;
int retry_plain = 0;
DSN_BUF *why = state->why;
/*
* First try to deliver to the indicated destination, then try to deliver
* to the optional fall-back relays.
*
* Future proofing: do a null destination sanity check in case we allow the
* primary destination to be a list (it could be just separators).
*/
sites = argv_alloc(1);
argv_add(sites, nexthop, (char *) 0);
if (sites->argc == 0)
msg_panic("null destination: \"%s\"", nexthop);
non_fallback_sites = sites->argc;
if ((state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0)
argv_split_append(sites, var_fallback_relay, ", \t\r\n");
/*
* Don't give up after a hard host lookup error until we have tried the
* fallback relay servers.
*
* Don't bounce mail after a host lookup problem with a relayhost or with a
* fallback relay.
*
* Don't give up after a qualifying soft error until we have tried all
* qualifying backup mail servers.
*
* All this means that error handling and error reporting depends on whether
* the error qualifies for trying to deliver to a backup mail server, or
* whether we're looking up a relayhost or fallback relay. The challenge
* then is to build this into the pre-existing SMTP client without
* getting lost in the complexity.
*/
#define IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites) \
(*(cpp) && (cpp) >= (sites)->argv + (non_fallback_sites))
for (cpp = sites->argv, (state->misc_flags |= SMTP_MISC_FLAG_FIRST_NEXTHOP);
SMTP_RCPT_LEFT(state) > 0 && (dest = *cpp) != 0;
cpp++, (state->misc_flags &= ~SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
char *dest_buf;
char *domain;
unsigned port;
DNS_RR *addr_list;
DNS_RR *addr;
DNS_RR *next;
int addr_count;
int sess_count;
SMTP_SESSION *session;
int lookup_mx;
unsigned domain_best_pref;
MAI_HOSTADDR_STR hostaddr;
if (cpp[1] == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
/*
* Parse the destination. Default is to use the SMTP port. Look up
* the address instead of the mail exchanger when a quoted host is
* specified, or when DNS lookups are disabled.
*/
dest_buf = smtp_parse_destination(dest, def_service, &domain, &port);
if (var_helpful_warnings && ntohs(port) == 465) {
msg_info("CLIENT wrappermode (port smtps/465) is unimplemented");
msg_info("instead, send to (port submission/587) with STARTTLS");
}
/*
* Resolve an SMTP server. Skip mail exchanger lookups when a quoted
* host is specified, or when DNS lookups are disabled.
*/
if (msg_verbose)
msg_info("connecting to %s port %d", domain, ntohs(port));
if ((state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) {
if (ntohs(port) == IPPORT_SMTP)
state->misc_flags |= SMTP_MISC_FLAG_LOOP_DETECT;
else
state->misc_flags &= ~SMTP_MISC_FLAG_LOOP_DETECT;
lookup_mx = (var_disable_dns == 0 && *dest != '[');
} else
lookup_mx = 0;
if (!lookup_mx) {
addr_list = smtp_host_addr(domain, state->misc_flags, why);
/* XXX We could be an MX host for this destination... */
} else {
int i_am_mx = 0;
addr_list = smtp_domain_addr(domain, state->misc_flags,
why, &i_am_mx);
/* If we're MX host, don't connect to non-MX backups. */
if (i_am_mx)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
}
/*
* Don't try fall-back hosts if mail loops to myself. That would just
* make the problem worse.
*/
if (addr_list == 0 && SMTP_HAS_LOOP_DSN(why))
state->misc_flags |= SMTP_MISC_FLAG_FINAL_NEXTHOP;
/*
* No early loop exit or we have a memory leak with dest_buf.
*/
if (addr_list)
domain_best_pref = addr_list->pref;
/*
* When session caching is enabled, store the first good session for
* this delivery request under the next-hop destination name. All
* good sessions will be stored under their specific server IP
* address.
*
* XXX Replace sites->argv by (lookup_mx, domain, port) triples so we
* don't have to make clumsy ad-hoc copies and keep track of who
* free()s the memory.
*
* XXX smtp_session_cache_destinations specifies domain names without
* :port, because : is already used for maptype:mapname. Because of
* this limitation we use the bare domain without the optional [] or
* non-default TCP port.
*
* Opportunistic (a.k.a. on-demand) session caching on request by the
* queue manager. This is turned temporarily when a destination has a
* high volume of mail in the active queue.
*
* XXX Disable connection caching when sender-dependent authentication
* is enabled. We must not send someone elses mail over an
* authenticated connection, and we must not send mail that requires
* authentication over a connection that wasn't authenticated.
*/
if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_FIRST_NEXTHOP)) {
smtp_cache_policy(state, domain);
if (state->misc_flags & SMTP_MISC_FLAG_CONN_STORE)
SET_NEXTHOP_STATE(state, lookup_mx, domain, port);
}
/*
* Delete visited cached hosts from the address list.
*
* Optionally search the connection cache by domain name or by primary
* MX address before we try to create new connections.
*
* Enforce the MX session and MX address counts per next-hop or
* fall-back destination. smtp_reuse_session() will truncate the
* address list when either limit is reached.
*/
if (addr_list && (state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD)) {
if (state->cache_used->used > 0)
smtp_scrub_addr_list(state->cache_used, &addr_list);
sess_count = addr_count =
smtp_reuse_session(state, lookup_mx, domain, port,
&addr_list, domain_best_pref);
} else
sess_count = addr_count = 0;
/*
* Connect to an SMTP server: create primary MX connections, and
* reuse or create backup MX connections.
*
* At the start of an SMTP session, all recipients are unmarked. In the
* course of an SMTP session, recipients are marked as KEEP (deliver
* to alternate mail server) or DROP (remove from recipient list). At
* the end of an SMTP session, weed out the recipient list. Unmark
* any left-over recipients and try to deliver them to a backup mail
* server.
*
* Cache the first good session under the next-hop destination name.
* Cache all good sessions under their physical endpoint.
*
* Don't query the session cache for primary MX hosts. We already did
* that in smtp_reuse_session(), and if any were found in the cache,
* they were already deleted from the address list.
*/
for (addr = addr_list; SMTP_RCPT_LEFT(state) > 0 && addr; addr = next) {
next = addr->next;
if (++addr_count == var_smtp_mxaddr_limit)
next = 0;
if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
|| addr->pref == domain_best_pref
|| dns_rr_to_pa(addr, &hostaddr) == 0
|| !(session = smtp_reuse_addr(state, hostaddr.buf, port)))
session = smtp_connect_addr(dest, addr, port, why,
state->misc_flags);
if ((state->session = session) != 0) {
session->state = state;
if (addr->pref == domain_best_pref)
session->features |= SMTP_FEATURE_BEST_MX;
/* Don't count handshake errors towards the session limit. */
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& next == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
#ifdef USE_TLS
/* Disable TLS when retrying after a handshake failure */
if (retry_plain) {
if (session->tls_level >= TLS_LEV_ENCRYPT)
msg_panic("Plain-text retry wrong for mandatory TLS");
session->tls_level = TLS_LEV_NONE;
retry_plain = 0;
}
session->tls_nexthop = domain; /* for TLS_LEV_SECURE */
#endif
if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
&& smtp_helo(state) != 0) {
#ifdef USE_TLS
/*
* When an opportunistic TLS handshake fails, try the
* same address again, with TLS disabled. See also the
* RETRY_AS_PLAINTEXT macro.
*/
if ((retry_plain = session->tls_retry_plain) != 0) {
--addr_count;
next = addr;
}
#endif
/*
* When a TLS handshake fails, the stream is marked
* "dead" to avoid further I/O over a broken channel.
*/
if (!THIS_SESSION_IS_DEAD
&& vstream_ferror(session->stream) == 0
&& vstream_feof(session->stream) == 0)
smtp_quit(state);
} else {
/* Do count delivery errors towards the session limit. */
if (++sess_count == var_smtp_mxsess_limit)
next = 0;
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
&& next == 0)
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
smtp_xfer(state);
}
smtp_cleanup_session(state);
} else {
/* The reason already includes the IP address and TCP port. */
msg_info("%s", STR(why->reason));
}
/* Insert: test if we must skip the remaining MX hosts. */
}
dns_rr_free(addr_list);
myfree(dest_buf);
if (state->misc_flags & SMTP_MISC_FLAG_FINAL_NEXTHOP)
break;
}
/*
* We still need to deliver, bounce or defer some left-over recipients:
* either mail loops or some backup mail server was unavailable.
*/
if (SMTP_RCPT_LEFT(state) > 0) {
/*
* In case of a "no error" indication we make up an excuse: we did
* find the host address, but we did not attempt to connect to it.
* This can happen when the fall-back relay was already tried via a
* cached connection, so that the address list scrubber left behind
* an empty list.
*/
if (!SMTP_HAS_DSN(why)) {
dsb_simple(why, "4.3.0",
"server unavailable or unable to receive mail");
}
/*
* Pay attention to what could be configuration problems, and pretend
* that these are recoverable rather than bouncing the mail.
*/
else if (!SMTP_HAS_SOFT_DSN(why)
&& (state->misc_flags & SMTP_MISC_FLAG_USE_LMTP) == 0) {
/*
* The fall-back destination did not resolve as expected, or it
* is refusing to talk to us, or mail for it loops back to us.
*/
if (IS_FALLBACK_RELAY(cpp, sites, non_fallback_sites)) {
msg_warn("%s configuration problem", VAR_SMTP_FALLBACK);
vstring_strcpy(why->status, "4.3.5");
/* XXX Keep the diagnostic code and MTA. */
}
/*
* The next-hop relayhost did not resolve as expected, or it is
* refusing to talk to us, or mail for it loops back to us.
*/
else if (strcmp(sites->argv[0], var_relayhost) == 0) {
msg_warn("%s configuration problem", VAR_RELAYHOST);
vstring_strcpy(why->status, "4.3.5");
/* XXX Keep the diagnostic code and MTA. */
}
/*
* Mail for the next-hop destination loops back to myself. Pass
* the mail to the best_mx_transport or bounce it.
*/
else if (SMTP_HAS_LOOP_DSN(why) && *var_bestmx_transp) {
dsb_reset(why); /* XXX */
state->status = deliver_pass_all(MAIL_CLASS_PRIVATE,
var_bestmx_transp,
request);
SMTP_RCPT_LEFT(state) = 0; /* XXX */
}
}
}
/*
* Cleanup.
*/
if (HAVE_NEXTHOP_STATE(state))
FREE_NEXTHOP_STATE(state);
argv_free(sites);
}
static void smtp_connect_local(SMTP_STATE *state, const char *path)
{
const char *myname = "smtp_connect_local";
SMTP_SESSION *session;
DSN_BUF *why = state->why;
/*
* It's too painful to weave this code into the SMTP connection
* management routine.
*
* Connection cache management is based on the UNIX-domain pathname, without
* the "unix:" prefix.
*/
smtp_cache_policy(state, path);
/*
* XXX We assume that the session->addr member refers to a copy of the
* UNIX-domain pathname, so that smtp_save_session() will cache the
* connection using the pathname as the physical endpoint name.
*/
#define NO_PORT 0
/*
* Opportunistic TLS for unix domain sockets does not make much sense,
* since the channel is private, mere encryption without authentication
* is just wasted cycles and opportunity for breakage. Since we are not
* willing to retry after TLS handshake failures here, we downgrade "may"
* no "none". Nothing is lost, and much waste is avoided.
*
* We don't know who is authenticating whom, so if a client cert is
* available, "encrypt" may be a sensible policy. Otherwise, we also
* downgrade "encrypt" to "none", this time just to avoid waste.
*/
if ((state->misc_flags & SMTP_MISC_FLAG_CONN_LOAD) == 0
|| (session = smtp_reuse_addr(state, path, NO_PORT)) == 0)
session = smtp_connect_unix(path, why, state->misc_flags);
if ((state->session = session) != 0) {
session->state = state;
#ifdef USE_TLS
session->tls_nexthop = var_myhostname; /* for TLS_LEV_SECURE */
if (session->tls_level == TLS_LEV_MAY) {
msg_warn("%s: opportunistic TLS encryption is not appropriate "
"for unix-domain destinations.", myname);
session->tls_level = TLS_LEV_NONE;
}
#endif
/* All delivery errors bounce or defer. */
state->misc_flags |= SMTP_MISC_FLAG_FINAL_SERVER;
/*
* When a TLS handshake fails, the stream is marked "dead" to avoid
* further I/O over a broken channel.
*/
if ((session->features & SMTP_FEATURE_FROM_CACHE) == 0
&& smtp_helo(state) != 0) {
if (!THIS_SESSION_IS_DEAD
&& vstream_ferror(session->stream) == 0
&& vstream_feof(session->stream) == 0)
smtp_quit(state);
} else {
smtp_xfer(state);
}
/*
* With opportunistic TLS disabled we don't expect to be asked to
* retry connections without TLS, and so we expect the final server
* flag to stay on.
*/
if ((state->misc_flags & SMTP_MISC_FLAG_FINAL_SERVER) == 0)
msg_panic("%s: unix-domain destination not final!", myname);
smtp_cleanup_session(state);
}
}