sip: UDP for the protected leg, TCP first with a fallback
imsd's protected leg (the second REGISTER and everything after it) was
TCP only. A P-CSCF that never answers the TCP connect on its protected
server port (O2 UK: the SYNs leave ESP-protected, nothing comes back)
left the unit looping with no way forward, although the SAs, the
listener sockets and the firewall rule already covered UDP.
The client flow now carries a transport. UDP binds the same protected
client port and connect()s the datagram socket to the P-CSCF's protected
server port, so the kernel delivers that peer's datagrams to it ahead of
the unconnected listener on the same port. One datagram is one message
(RFC 3261 18.3: a Content-Length that fits truncates, one that does not
fit discards the datagram, none means the rest of the datagram); a
receive error is logged and marks the flow dead; a message over the
single-packet ESP budget at the ims PDN's MTU is logged once per flow,
since the kernel fragments it and a P-CSCF may drop the fragments.
Every protected request's Via follows the transport; the challenge
stays UDP.
SIP_TRANSPORT selects the policy: auto (default) registers over TCP and,
after two unanswered connects, registers again over UDP (new challenge,
new SA pair) - but only on a phone whose state file does not record a
successful TCP registration, so an outage on a TCP carrier never becomes
a second initial REGISTER; a phone whose last registration was UDP goes
straight to UDP. tcp and udp force one. A connect refused locally
(EADDRNOTAVAIL: the 4-tuple still in TIME_WAIT from the previous flow)
keeps retrying and is not counted as silence; SO_ERROR results are
logged by name. The registration's transport is persisted so a warm
resume reconnects the same way, and the resume gives up after two
silences.
Two things the change exposed and fixes: an engine-fatal event exited 0
("exiting for systemd restart" with Restart=on-failure never firing),
and a fresh registration refused with the P-CSCF's fresh-SA throttle
(Security-Server spi-s=0) must not be retried by a 120-s restart loop,
since every attempt re-arms the ~20-min window - it is now waited out
in-process, growing on repeats, with D-Bus commands still served. A
resume the network refuses falls through to a fresh registration. A
retransmitted 200 OK to our INVITE is ACKed again and no longer starts
a second media leg.
Verified on KPN: resume over TCP after a binary swap, MT and MO calls
with media both ways, the throttle deferral and its self-recovery, the
UDP client path up to KPN dropping the datagram. The UDP success path
is a field test; SIP retransmission timers over UDP are not in this
change.
This commit is contained in:
parent
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GPG key ID:
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8 changed files with 292 additions and 29 deletions
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@ -37,6 +37,10 @@ export namespace imsd::msg {
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int portUc = imsd::util::PortUc;
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int portUs = imsd::util::PortUs;
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int initPort = 5060;
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// Transport of the protected leg (REGISTER 2 onwards): the Via token
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// of every request we send over it. TCP unless the engine fell back
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// to, or was told to use, UDP.
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std::string transport = "TCP";
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std::string ealgOffer = "aes-cbc";
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// RFC 7254 IMEI URN for +sip.instance (e.g. urn:gsma:imei:35999999-
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// 000000-1); empty omits the parameter.
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@ -218,7 +222,7 @@ export namespace imsd::msg {
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std::string BuildRegisterProtected(const Context& c, std::string_view callid, std::string_view ftag, std::string_view branch, int cseq, std::uint32_t spiUc, std::uint32_t spiUs, std::string_view authLine) {
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std::vector<std::string> l = {
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std::format("REGISTER {} SIP/2.0", c.id.regUri),
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ViaLine(c, "TCP", c.portUs, branch),
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ViaLine(c, c.transport, c.portUs, branch),
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"Max-Forwards: 70",
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std::format("From: <{}>;tag={}", c.id.impu, ftag),
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std::format("To: <{}>", c.id.impu),
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@ -252,7 +256,7 @@ export namespace imsd::msg {
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: std::string_view(c.aor);
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std::vector<std::string> l = {
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std::format("SUBSCRIBE {} SIP/2.0", aor),
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ViaLine(c, "TCP", c.portUs, branch),
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ViaLine(c, c.transport, c.portUs, branch),
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"Max-Forwards: 70",
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std::format("Route: {}", c.route),
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std::format("From: <{}>;tag={}", aor, ftag),
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@ -331,7 +335,7 @@ export namespace imsd::msg {
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: "100rel, timer";
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std::vector<std::string> l = {
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std::format("INVITE {} SIP/2.0", d.ruri),
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std::format("Via: SIP/2.0/TCP {};branch=z9hG4bK{};rport", imsd::util::HostPort(c.local, c.portUs), d.invBranch),
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ViaLine(c, c.transport, c.portUs, d.invBranch),
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"Max-Forwards: 70",
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std::format("Route: {}", c.route),
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std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
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@ -364,7 +368,7 @@ export namespace imsd::msg {
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std::string to = d.dialogTo.value_or(std::format("<{}>", d.ruri));
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std::vector<std::string> l = {
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std::format("{} {} SIP/2.0", method, target),
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ViaLine(c, "TCP", c.portUs, viaBranch),
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ViaLine(c, c.transport, c.portUs, viaBranch),
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"Max-Forwards: 70",
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std::format("Route: {}", DialogRoute(c, d)),
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std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
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@ -391,7 +395,7 @@ export namespace imsd::msg {
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std::string to = d.dialogTo.value_or(std::string(toHeader));
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std::vector<std::string> l = {
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std::format("ACK {} SIP/2.0", target),
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ViaLine(c, "TCP", c.portUs, viaBranch),
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ViaLine(c, c.transport, c.portUs, viaBranch),
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"Max-Forwards: 70",
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std::format("Route: {}", DialogRoute(c, d)),
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std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
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@ -408,7 +412,7 @@ export namespace imsd::msg {
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std::string BuildAckNon2xx(const Context& c, const Dialog& d, std::string_view toHeader) {
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std::vector<std::string> l = {
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std::format("ACK {} SIP/2.0", d.ruri),
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std::format("Via: SIP/2.0/TCP {};branch=z9hG4bK{};rport", imsd::util::HostPort(c.local, c.portUs), d.invBranch),
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ViaLine(c, c.transport, c.portUs, d.invBranch),
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"Max-Forwards: 70",
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std::format("Route: {}", c.route),
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std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
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@ -424,7 +428,7 @@ export namespace imsd::msg {
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std::string BuildCancel(const Context& c, const Dialog& d) {
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std::vector<std::string> l = {
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std::format("CANCEL {} SIP/2.0", d.ruri),
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std::format("Via: SIP/2.0/TCP {};branch=z9hG4bK{};rport", imsd::util::HostPort(c.local, c.portUs), d.invBranch),
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ViaLine(c, c.transport, c.portUs, d.invBranch),
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"Max-Forwards: 70",
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std::format("Route: {}", c.route),
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std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
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