diff options
| author | Thomas Haller <thaller@redhat.com> | 2016-11-30 15:09:41 +0100 |
|---|---|---|
| committer | Thomas Haller <thaller@redhat.com> | 2016-11-30 15:40:26 +0100 |
| commit | 55ea6e6b6cd805f441b410971c9dd7575e783ef4 (patch) | |
| tree | 674fa1461f678f54aa8750c72ffcaaf69945f559 /include | |
| parent | 6f9620721200d171d6a317573b3c1c00141f036b (diff) | |
| download | libnl-55ea6e6b6cd805f441b410971c9dd7575e783ef4.tar.gz | |
lib: use MSG_PEEK by default for nl_recvmsgs()
The MSG_PEEK API of recvmsg() should be avoid because it requires an additional
syscall. But worse is to choose a too small buffer size and failing to receive
the message.
A user who is aware of the issue can avoid MSG_PEEK by either
nl_socket_disable_msg_peek()/nl_socket_enable_msg_peek() or by setting
a buffer size via nl_socket_set_msg_buf_size().
By default however we now use MSG_PEEK. This is more important since commit
90c6ebec9bd7a where the link dump request can be rather large.
Signed-off-by: Thomas Haller <thaller@redhat.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/netlink-private/types.h | 3 | ||||
| -rw-r--r-- | include/netlink/utils.h | 15 |
2 files changed, 17 insertions, 1 deletions
diff --git a/include/netlink-private/types.h b/include/netlink-private/types.h index d8c0e3fd..1b19b584 100644 --- a/include/netlink-private/types.h +++ b/include/netlink-private/types.h @@ -29,7 +29,8 @@ #define NL_SOCK_PASSCRED (1<<1) #define NL_OWN_PORT (1<<2) #define NL_MSG_PEEK (1<<3) -#define NL_NO_AUTO_ACK (1<<4) +#define NL_MSG_PEEK_EXPLICIT (1<<4) +#define NL_NO_AUTO_ACK (1<<5) #define NL_MSG_CRED_PRESENT 1 diff --git a/include/netlink/utils.h b/include/netlink/utils.h index 6f984e18..a2ffe4b1 100644 --- a/include/netlink/utils.h +++ b/include/netlink/utils.h @@ -246,6 +246,21 @@ enum { NL_CAPABILITY_LINK_BUILD_ADD_REQUEST_SET_CHANGE = 23, #define NL_CAPABILITY_LINK_BUILD_ADD_REQUEST_SET_CHANGE NL_CAPABILITY_LINK_BUILD_ADD_REQUEST_SET_CHANGE + /* Older versions of libnl3 would not use MSG_PEEK for nl_recvmsgs() unless calling + * nl_socket_enable_msg_peek(). Instead, the user had to specify the buffer size via + * nl_socket_set_msg_buf_size(), which in turn would default to 4*getpagesize(). + * + * The default value might not be large enough, so users who were not aware of the + * problem easily ended up using a too small receive buffer. Usually, one wants to + * avoid MSG_PEEK for recvmsg() because it requires an additional syscall. + * + * Now, as indicated by this capability, nl_recvmsgs() would use MSG_PEEK by default. The + * user still can explicitly disable MSG_PEEK by calling nl_socket_disable_msg_peek() or + * by setting the nl_socket_set_msg_buf_size() to a non-zero value. + */ + NL_CAPABILITY_NL_RECVMSGS_PEEK_BY_DEFAULT = 24, +#define NL_CAPABILITY_NL_RECVMSGS_PEEK_BY_DEFAULT NL_CAPABILITY_NL_RECVMSGS_PEEK_BY_DEFAULT + __NL_CAPABILITY_MAX, NL_CAPABILITY_MAX = (__NL_CAPABILITY_MAX - 1), #define NL_CAPABILITY_MAX NL_CAPABILITY_MAX |