From 5265fabeb98dc2af702a56f1a4b45627c3d4d93f Mon Sep 17 00:00:00 2001 From: Matthieu Kermagoret Date: Mon, 3 Feb 2014 16:49:21 +0100 Subject: Use kernel reception time on ICMP packets to compute rtt. This commit uses the SO_TIMESTAMP feature of setsockopt to fetch kernel reception time of ICMP packets. This avoids invalid computations of rtt on machines with heavy load and/or heavy network traffic. --- plugins-root/check_icmp.c | 55 +++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 48 insertions(+), 7 deletions(-) diff --git a/plugins-root/check_icmp.c b/plugins-root/check_icmp.c index 8b563e40..d2f637fd 100644 --- a/plugins-root/check_icmp.c +++ b/plugins-root/check_icmp.c @@ -184,7 +184,7 @@ static u_int get_timevar(const char *); static u_int get_timevaldiff(struct timeval *, struct timeval *); static in_addr_t get_ip_address(const char *); static int wait_for_reply(int, u_int); -static int recvfrom_wto(int, void *, unsigned int, struct sockaddr *, u_int *); +static int recvfrom_wto(int, void *, unsigned int, struct sockaddr *, u_int *, struct timeval*); static int send_icmp_ping(int, struct rta_host *); static int get_threshold(char *str, threshold *th); static void run_checks(void); @@ -402,6 +402,12 @@ main(int argc, char **argv) /* now drop privileges (no effect if not setsuid or geteuid() == 0) */ setuid(getuid()); +#ifdef SO_TIMESTAMP + int on = 1; + if(setsockopt(icmp_sock, SOL_SOCKET, SO_TIMESTAMP, &on, sizeof(on))) + if(debug) printf("Warning: no SO_TIMESTAMP support\n"); +#endif // SO_TIMESTAMP + /* POSIXLY_CORRECT might break things, so unset it (the portable way) */ environ = NULL; @@ -727,7 +733,7 @@ wait_for_reply(int sock, u_int t) /* reap responses until we hit a timeout */ n = recvfrom_wto(sock, buf, sizeof(buf), - (struct sockaddr *)&resp_addr, &t); + (struct sockaddr *)&resp_addr, &t, &now); if(!n) { if(debug > 1) { printf("recvfrom_wto() timed out during a %u usecs wait\n", @@ -781,7 +787,6 @@ wait_for_reply(int sock, u_int t) sizeof(data), ntohs(icp.icmp_id), ntohs(icp.icmp_seq), icp.icmp_cksum); host = table[ntohs(icp.icmp_seq)/packets]; - gettimeofday(&now, &tz); tdiff = get_timevaldiff(&data.stime, &now); host->time_waited += tdiff; @@ -858,8 +863,17 @@ send_icmp_ping(int sock, struct rta_host *host) printf("Sending ICMP echo-request of len %u, id %u, seq %u, cksum 0x%X to host %s\n", sizeof(data), ntohs(packet.icp->icmp_id), ntohs(packet.icp->icmp_seq), packet.icp->icmp_cksum, host->name); - len = sendto(sock, packet.buf, icmp_pkt_size, 0, (struct sockaddr *)addr, - sizeof(struct sockaddr)); + struct msghdr hdr; + memset(&hdr, 0, sizeof(hdr)); + hdr.msg_name = addr; + hdr.msg_namelen = sizeof(struct sockaddr); + struct iovec iov; + memset(&iov, 0, sizeof(iov)); + iov.iov_base = packet.buf; + iov.iov_len = icmp_pkt_size; + hdr.msg_iov = &iov; + hdr.msg_iovlen = 1; + len = sendmsg(sock, &hdr, MSG_CONFIRM); if(len < 0 || (unsigned int)len != icmp_pkt_size) { if(debug) printf("Failed to send ping to %s\n", @@ -875,7 +889,7 @@ send_icmp_ping(int sock, struct rta_host *host) static int recvfrom_wto(int sock, void *buf, unsigned int len, struct sockaddr *saddr, - u_int *timo) + u_int *timo, struct timeval* tv) { u_int slen; int n; @@ -904,7 +918,34 @@ recvfrom_wto(int sock, void *buf, unsigned int len, struct sockaddr *saddr, slen = sizeof(struct sockaddr); - return recvfrom(sock, buf, len, 0, saddr, &slen); + struct msghdr hdr; + memset(&hdr, 0, sizeof(hdr)); + hdr.msg_name = saddr; + hdr.msg_namelen = slen; + struct iovec iov; + memset(&iov, 0, sizeof(iov)); + iov.iov_base = buf; + iov.iov_len = len; + hdr.msg_iov = &iov; + hdr.msg_iovlen = 1; + char ans_data[4096]; + hdr.msg_control = ans_data; + hdr.msg_controllen = sizeof(ans_data); + int ret = recvmsg(sock, &hdr, 0); +#ifdef SO_TIMESTAMP + struct cmsghdr* chdr; + for(chdr = CMSG_FIRSTHDR(&hdr); chdr; chdr = CMSG_NXTHDR(&hdr, chdr)) { + if(chdr->cmsg_level == SOL_SOCKET + && chdr->cmsg_type == SO_TIMESTAMP + && chdr->cmsg_len >= CMSG_LEN(sizeof(struct timeval))) { + memcpy(tv, CMSG_DATA(chdr), sizeof(*tv)); + break ; + } + } + if (!chdr) +#endif // SO_TIMESTAMP + gettimeofday(tv, &tz); + return (ret); } static void -- cgit v1.2.3-74-g34f1