dhcp: don't stop receiving packets when the link goes down

When the link goes down, DHCP client_receive_message*() functions return an
error and the related I/O source is removed from the main loop. With the
current implementation of systemd-networkd this doesn't matter because the DHCP
client is always stopped on carrier down and restarted on carrier up. However
it seems wrong to have the DHCP client crippled (because no packet can be
received anymore) once the link goes temporarily down.

Change the receive functions to ignore a ENETDOWN event so that the client will
be able to receive packets again after the link comes back.

diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index ece163124a8e9a75d5ced872d83219c8576c2645..7975cfecf5b815d7e319f4c8c49c1cbd6c26329a 100644 (file)
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -1684,6 +1684,12 @@ static int client_receive_message_udp(
         assert(client);
 
         buflen = next_datagram_size_fd(fd);
+        if (buflen == -ENETDOWN) {
+                /* the link is down. Don't return an error or the I/O event
+                   source will be disconnected and we won't be able to receive
+                   packets again when the link comes back. */
+                return 0;
+        }
         if (buflen < 0)
                 return buflen;
 
@@ -1693,7 +1699,8 @@ static int client_receive_message_udp(
 
         len = recv(fd, message, buflen, 0);
         if (len < 0) {
-                if (IN_SET(errno, EAGAIN, EINTR))
+                /* see comment above for why we shouldn't error out on ENETDOWN. */
+                if (IN_SET(errno, EAGAIN, EINTR, ENETDOWN))
                         return 0;
 
                 return log_dhcp_client_errno(client, errno,
@@ -1771,6 +1778,8 @@ static int client_receive_message_raw(
         assert(client);
 
         buflen = next_datagram_size_fd(fd);
+        if (buflen == -ENETDOWN)
+                return 0;
         if (buflen < 0)
                 return buflen;
 
@@ -1782,7 +1791,7 @@ static int client_receive_message_raw(
 
         len = recvmsg(fd, &msg, 0);
         if (len < 0) {
-                if (IN_SET(errno, EAGAIN, EINTR))
+                if (IN_SET(errno, EAGAIN, EINTR, ENETDOWN))
                         return 0;
 
                 return log_dhcp_client_errno(client, errno,

diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
index 593ffd1b644fed6d88693488760f361190ff8229..68b41dfb6cd777a9b6278358103d230a3f95eb88 100644 (file)
--- a/src/libsystemd-network/sd-dhcp6-client.c
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -1112,6 +1112,12 @@ static int client_receive_message(
         assert(client->event);
 
         buflen = next_datagram_size_fd(fd);
+        if (buflen == -ENETDOWN) {
+                /* the link is down. Don't return an error or the I/O event
+                   source will be disconnected and we won't be able to receive
+                   packets again when the link comes back. */
+                return 0;
+        }
         if (buflen < 0)
                 return buflen;
 
@@ -1121,7 +1127,8 @@ static int client_receive_message(
 
         len = recv(fd, message, buflen, 0);
         if (len < 0) {
-                if (IN_SET(errno, EAGAIN, EINTR))
+                /* see comment above for why we shouldn't error out on ENETDOWN. */
+                if (IN_SET(errno, EAGAIN, EINTR, ENETDOWN))
                         return 0;
 
                 return log_dhcp6_client_errno(client, errno, "Could not receive message from UDP socket: %m");