netns: improve netnsid allocation

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/network.c b/src/lxc/network.c
index d0824690fcbc9f51cf2a1050de14724b48328bd2..53bc581114b96b22cbe7418e5cb360b3ca77c54b 100644 (file)
--- a/src/lxc/network.c
+++ b/src/lxc/network.c
@@ -3192,16 +3192,102 @@ enum {
        __LXC_NETNSA_MAX,
 };
 
+static int nl_send(struct nl_handler *handler, struct nlmsghdr *nlmsghdr)
+{
+       struct sockaddr_nl nladdr;
+       struct iovec iov = {
+               .iov_base = nlmsghdr,
+               .iov_len = nlmsghdr->nlmsg_len,
+       };
+       struct msghdr msg = {
+               .msg_name = &nladdr,
+               .msg_namelen = sizeof(nladdr),
+               .msg_iov = &iov,
+               .msg_iovlen = 1,
+       };
+       int ret;
+
+       memset(&nladdr, 0, sizeof(nladdr));
+       nladdr.nl_family = AF_NETLINK;
+       nladdr.nl_pid = 0;
+       nladdr.nl_groups = 0;
+
+       ret = sendmsg(handler->fd, &msg, MSG_NOSIGNAL);
+       if (ret < 0)
+               return -errno;
+
+       return ret;
+}
+
+static int nl_recv(struct nl_handler *handler, struct nlmsghdr *nlmsghdr)
+{
+       int ret;
+       struct sockaddr_nl nladdr;
+       struct iovec iov = {
+           .iov_base = nlmsghdr,
+           .iov_len = nlmsghdr->nlmsg_len,
+       };
+
+       struct msghdr msg = {
+               .msg_name = &nladdr,
+               .msg_namelen = sizeof(nladdr),
+               .msg_iov = &iov,
+               .msg_iovlen = 1,
+       };
+
+       memset(&nladdr, 0, sizeof(nladdr));
+       nladdr.nl_family = AF_NETLINK;
+       nladdr.nl_pid = 0;
+       nladdr.nl_groups = 0;
+
+again:
+       ret = recvmsg(handler->fd, &msg, 0);
+       if (ret < 0) {
+               if (errno == EINTR)
+                       goto again;
+
+               return -1;
+       }
+
+       if (!ret)
+               return 0;
+
+       if (msg.msg_flags & MSG_TRUNC && (ret == nlmsghdr->nlmsg_len))
+               return -EMSGSIZE;
+
+       return ret;
+}
+
+extern int nl_transaction(struct nl_handler *handler, struct nlmsghdr *request,
+                         struct nlmsghdr *answer)
+{
+       int ret;
+
+       ret = nl_send(handler, request);
+       if (ret < 0)
+               return ret;
+
+       ret = nl_recv(handler, answer);
+       if (ret < 0)
+               return ret;
+
+       if (answer->nlmsg_type == NLMSG_ERROR) {
+               struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(answer);
+               return err->error;
+       }
+
+       return 0;
+}
+
 int lxc_netns_set_nsid(int fd)
 {
        ssize_t ret;
-       char l_buffer[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
-                     NLMSG_ALIGN(sizeof(struct rtgenmsg)) +
-                     NLMSG_ALIGN(1024)];
+       char buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+                NLMSG_ALIGN(sizeof(struct rtgenmsg)) +
+                NLMSG_ALIGN(1024)];
        struct nl_handler nlh;
-       struct nlmsghdr *l_hdr;
-       struct rtgenmsg *l_msg;
-       struct sockaddr_nl l_addr;
+       struct nlmsghdr *hdr;
+       struct rtgenmsg *msg;
        __s32 ns_id = -1;
        __u32 netns_fd = fd;
 
@@ -3209,25 +3295,21 @@ int lxc_netns_set_nsid(int fd)
        if (ret < 0)
                return ret;
 
-       memset(l_buffer, 0, sizeof(l_buffer));
-       l_hdr = (struct nlmsghdr *)l_buffer;
-       l_msg = (struct rtgenmsg *)NLMSG_DATA(l_hdr);
-
-       l_hdr->nlmsg_len = NLMSG_LENGTH(sizeof(*l_msg));
-       l_hdr->nlmsg_type = RTM_NEWNSID;
-       l_hdr->nlmsg_flags = NLM_F_REQUEST;
-       l_hdr->nlmsg_pid = 0;
-       l_hdr->nlmsg_seq = RTM_NEWNSID;
-       l_msg->rtgen_family = AF_UNSPEC;
+       memset(buf, 0, sizeof(buf));
+       hdr = (struct nlmsghdr *)buf;
+       msg = (struct rtgenmsg *)NLMSG_DATA(hdr);
 
-       addattr(l_hdr, 1024, __LXC_NETNSA_FD, &netns_fd, sizeof(netns_fd));
-       addattr(l_hdr, 1024, __LXC_NETNSA_NSID, &ns_id, sizeof(ns_id));
+       hdr->nlmsg_len = NLMSG_LENGTH(sizeof(*msg));
+       hdr->nlmsg_type = RTM_NEWNSID;
+       hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+       hdr->nlmsg_pid = 0;
+       hdr->nlmsg_seq = RTM_NEWNSID;
+       msg->rtgen_family = AF_UNSPEC;
 
-       memset(&l_addr, 0, sizeof(l_addr));
-       l_addr.nl_family = AF_NETLINK;
+       addattr(hdr, 1024, __LXC_NETNSA_FD, &netns_fd, sizeof(netns_fd));
+       addattr(hdr, 1024, __LXC_NETNSA_NSID, &ns_id, sizeof(ns_id));
 
-       ret = sendto(nlh.fd, l_hdr, l_hdr->nlmsg_len, 0,
-                    (struct sockaddr *)&l_addr, sizeof(l_addr));
+       ret = nl_transaction(&nlh, hdr, hdr);
        netlink_close(&nlh);
        if (ret < 0)
                return -1;