Merge ~alfonsosanchezbeato/snappy-hwe-snaps/+git/network-manager:fix-dhcp-busy-loop into ~snappy-hwe-team/snappy-hwe-snaps/+git/network-manager:network-manager/xenial/1.2.2

[Alfonso Sanchez-Beato]

Use recv() instead of read() when reading DHCP packets

This applies systemd commit cf447cb62 to fix a busy loop when an empty
DHCP UDP package has been (LP: #1790974).

[Konrad Zapałowicz (kzapalowicz)]

Ack

review: Approve

[Alfonso Sanchez-Beato (alfonsosanchezbeato)]

review: Approve (continuous-integration)

[System Enablement Bot (system-enablement-ci-bot)]

PASSED: Continuous integration, rev:f3a9eb6524d947a79e0fd619f3965415332e9bed
https://jenkins.canonical.com/system-enablement/job/snappy-hwe-snaps-snap-build-prepare/271/
Executed test runs:
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    SUCCESS: https://jenkins.canonical.com/system-enablement/job/snappy-hwe-snaps-snap-build/ARCHITECTURE=armhf/314
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    SUCCESS: https://jenkins.canonical.com/system-enablement/job/snappy-hwe-snaps-snap-docs/1106
    SUCCESS: https://jenkins.canonical.com/system-enablement/job/snappy-hwe-snaps-snap-cleanup/849
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review: Approve (continuous-integration)

diff --git a/src/systemd/src/libsystemd-network/sd-dhcp-client.c b/src/systemd/src/libsystemd-network/sd-dhcp-client.c
index 758dba4..5ca3b4d 100644
--- a/src/systemd/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/systemd/src/libsystemd-network/sd-dhcp-client.c
@@ -1591,7 +1591,7 @@ static int client_receive_message_udp(sd_event_source *s, int fd,
         if (!message)
                 return -ENOMEM;
 
-        len = read(fd, message, buflen);
+        len = recv(fd, message, buflen, 0);
         if (len < 0) {
                 if (errno == EAGAIN || errno == EINTR)
                         return 0;
diff --git a/src/systemd/src/libsystemd-network/sd-dhcp6-client.c b/src/systemd/src/libsystemd-network/sd-dhcp6-client.c
index 8fa1822..d9ef249 100644
--- a/src/systemd/src/libsystemd-network/sd-dhcp6-client.c
+++ b/src/systemd/src/libsystemd-network/sd-dhcp6-client.c
@@ -899,7 +899,7 @@ static int client_receive_message(sd_event_source *s, int fd, uint32_t revents, 
         if (!message)
                 return -ENOMEM;
 
-        len = read(fd, message, buflen);
+        len = recv(fd, message, buflen, 0);
         if (len < 0) {
                 if (errno == EAGAIN || errno == EINTR)
                         return 0;
diff --git a/src/systemd/src/libsystemd-network/sd-ipv4acd.c b/src/systemd/src/libsystemd-network/sd-ipv4acd.c
index 9b5ce72..867987c 100644
--- a/src/systemd/src/libsystemd-network/sd-ipv4acd.c
+++ b/src/systemd/src/libsystemd-network/sd-ipv4acd.c
@@ -157,8 +157,10 @@ static void ipv4acd_set_state(sd_ipv4acd *ll, IPv4ACDState st, bool reset_counte
 static void ipv4acd_client_notify(sd_ipv4acd *ll, int event) {
         assert(ll);
 
-        if (ll->cb)
-                ll->cb(ll, event, ll->userdata);
+        if (!ll->cb)
+                return;
+
+        ll->cb(ll, event, ll->userdata);
 }
 
 static void ipv4acd_stop(sd_ipv4acd *ll) {
@@ -348,22 +350,36 @@ static void ipv4acd_on_conflict(sd_ipv4acd *ll) {
         ipv4acd_client_notify(ll, SD_IPV4ACD_EVENT_CONFLICT);
 }
 
-static int ipv4acd_on_packet(sd_event_source *s, int fd,
-                            uint32_t revents, void *userdata) {
+static int ipv4acd_on_packet(
+                sd_event_source *s,
+                int fd,
+                uint32_t revents,
+                void *userdata) {
+
         sd_ipv4acd *ll = userdata;
         struct ether_arp packet;
+        ssize_t n;
         int r;
 
+        assert(s);
         assert(ll);
         assert(fd >= 0);
 
-        r = read(fd, &packet, sizeof(struct ether_arp));
-        if (r < (int) sizeof(struct ether_arp))
+        n = recv(fd, &packet, sizeof(struct ether_arp), 0);
+        if (n < 0) {
+                r = log_ipv4acd_debug_errno(ll, errno, "Failed to read ARP packet: %m");
                 goto out;
+        }
+        if ((size_t) n != sizeof(struct ether_arp)) {
+                log_ipv4acd_debug(ll, "Ignoring too short ARP packet.");
+                return 0;
+        }
 
         switch (ll->state) {
+
         case IPV4ACD_STATE_ANNOUNCING:
         case IPV4ACD_STATE_RUNNING:
+
                 if (ipv4acd_arp_conflict(ll, &packet)) {
                         usec_t ts;
 
@@ -382,15 +398,15 @@ static int ipv4acd_on_packet(sd_event_source *s, int fd,
                         } else
                                 ipv4acd_on_conflict(ll);
                 }
-
                 break;
+
         case IPV4ACD_STATE_WAITING_PROBE:
         case IPV4ACD_STATE_PROBING:
         case IPV4ACD_STATE_WAITING_ANNOUNCE:
                 /* BPF ensures this packet indicates a conflict */
                 ipv4acd_on_conflict(ll);
-
                 break;
+
         default:
                 assert_not_reached("Invalid state.");
         }