ctdb-common: Factor out TCP packet parsing code

This can be tested separately.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

diff --git a/ctdb/common/system_socket.c b/ctdb/common/system_socket.c
index 7adb55040f4134985389c5ca83e49db3f7740657..8de70f8bca628f19a0c0860e5a687c61037b60e4 100644 (file)
--- a/ctdb/common/system_socket.c
+++ b/ctdb/common/system_socket.c
@@ -736,6 +736,116 @@ int ctdb_sys_send_tcp(const ctdb_sock_addr *dest,
  * wscript has checked to make sure that pcap is available if needed.
  */
 
+static int tcp4_extract(const uint8_t *ip_pkt,
+                       size_t pktlen,
+                       struct sockaddr_in *src,
+                       struct sockaddr_in *dst,
+                       uint32_t *ack_seq,
+                       uint32_t *seq,
+                       int *rst,
+                       uint16_t *window)
+{
+       const struct ip *ip;
+       const struct tcphdr *tcp;
+
+       if (pktlen < sizeof(struct ip)) {
+               return EMSGSIZE;
+       }
+
+       /* IP */
+       ip = (const struct ip *)ip_pkt;
+
+       /* We only want IPv4 packets */
+       if (ip->ip_v != 4) {
+               return ENOMSG;
+       }
+       /* Dont look at fragments */
+       if ((ntohs(ip->ip_off)&0x1fff) != 0) {
+               return ENOMSG;
+       }
+       /* we only want TCP */
+       if (ip->ip_p != IPPROTO_TCP) {
+               return ENOMSG;
+       }
+
+       /* make sure its not a short packet */
+       if (offsetof(struct tcphdr, th_ack) + 4 + (ip->ip_hl*4) > pktlen) {
+               return EMSGSIZE;
+       }
+
+       /* TCP */
+       tcp = (const struct tcphdr *)((ip->ip_hl*4) + (const char *)ip);
+
+       /* tell the caller which one we've found */
+       src->sin_family      = AF_INET;
+       src->sin_addr.s_addr = ip->ip_src.s_addr;
+       src->sin_port        = tcp->th_sport;
+
+       dst->sin_family      = AF_INET;
+       dst->sin_addr.s_addr = ip->ip_dst.s_addr;
+       dst->sin_port        = tcp->th_dport;
+
+       *ack_seq             = tcp->th_ack;
+       *seq                 = tcp->th_seq;
+       if (window != NULL) {
+               *window = tcp->th_win;
+       }
+       if (rst != NULL) {
+               *rst = tcp->th_flags & TH_RST;
+       }
+
+       return 0;
+}
+
+static int tcp6_extract(const uint8_t *ip_pkt,
+                       size_t pktlen,
+                       struct sockaddr_in6 *src,
+                       struct sockaddr_in6 *dst,
+                       uint32_t *ack_seq,
+                       uint32_t *seq,
+                       int *rst,
+                       uint16_t *window)
+{
+       const struct ip6_hdr *ip6;
+       const struct tcphdr *tcp;
+
+       if (pktlen < sizeof(struct ip6_hdr)) {
+               return EMSGSIZE;
+       }
+
+       /* IP6 */
+       ip6 = (const struct ip6_hdr *)ip_pkt;
+
+       /* we only want TCP */
+       if (ip6->ip6_nxt != IPPROTO_TCP) {
+               return ENOMSG;
+       }
+
+       /* TCP */
+       tcp = (const struct tcphdr *)(ip6+1);
+
+       /* tell the caller which one we've found */
+       src->sin6_family = AF_INET6;
+       src->sin6_port   = tcp->th_sport;
+       src->sin6_addr   = ip6->ip6_src;
+
+       dst->sin6_family = AF_INET6;
+       dst->sin6_port   = tcp->th_dport;
+       dst->sin6_addr   = ip6->ip6_dst;
+
+       *ack_seq             = tcp->th_ack;
+       *seq                 = tcp->th_seq;
+       if (window != NULL) {
+               *window = tcp->th_win;
+       }
+       if (rst != NULL) {
+               *rst = tcp->th_flags & TH_RST;
+       }
+
+       return 0;
+}
+
+
 #ifdef HAVE_AF_PACKET
 
 /*
@@ -792,13 +902,10 @@ int ctdb_sys_read_tcp_packet(int s, void *private_data,
        ssize_t nread;
        uint8_t pkt[100]; /* Large enough for simple ACK/RST packets */
        struct ether_header *eth;
-       struct iphdr *ip;
-       struct ip6_hdr *ip6;
-       struct tcphdr *tcp;
        int ret;
 
        nread = recv(s, pkt, sizeof(pkt), MSG_TRUNC);
-       if (nread < sizeof(*eth)+sizeof(*ip)) {
+       if (nread < sizeof(*eth)) {
                return EMSGSIZE;
        }
 
@@ -810,78 +917,26 @@ int ctdb_sys_read_tcp_packet(int s, void *private_data,
 
        /* we want either IPv4 or IPv6 */
        if (ntohs(eth->ether_type) == ETHERTYPE_IP) {
-               /* IP */
-               ip = (struct iphdr *)(eth+1);
-
-               /* We only want IPv4 packets */
-               if (ip->version != 4) {
-                       return ENOMSG;
-               }
-               /* Dont look at fragments */
-               if ((ntohs(ip->frag_off)&0x1fff) != 0) {
-                       return ENOMSG;
-               }
-               /* we only want TCP */
-               if (ip->protocol != IPPROTO_TCP) {
-                       return ENOMSG;
-               }
-
-               /* make sure its not a short packet */
-               if (offsetof(struct tcphdr, th_ack) + 4 +
-                   (ip->ihl*4) + sizeof(*eth) > nread) {
-                       return EMSGSIZE;
-               }
-               /* TCP */
-               tcp = (struct tcphdr *)((ip->ihl*4) + (char *)ip);
-
-               /* tell the caller which one we've found */
-               src->ip.sin_family      = AF_INET;
-               src->ip.sin_addr.s_addr = ip->saddr;
-               src->ip.sin_port        = tcp->th_sport;
-               dst->ip.sin_family      = AF_INET;
-               dst->ip.sin_addr.s_addr = ip->daddr;
-               dst->ip.sin_port        = tcp->th_dport;
-               *ack_seq                = tcp->th_ack;
-               *seq                    = tcp->th_seq;
-               if (window != NULL) {
-                       *window = tcp->th_win;
-               }
-               if (rst != NULL) {
-                       *rst = tcp->th_flags & TH_RST;
-               }
+               ret = tcp4_extract(pkt + sizeof(struct ether_header),
+                                  (size_t)nread - sizeof(struct ether_header),
+                                  &src->ip,
+                                  &dst->ip,
+                                  ack_seq,
+                                  seq,
+                                  rst,
+                                  window);
+               return ret;
 
-               return 0;
        } else if (ntohs(eth->ether_type) == ETHERTYPE_IP6) {
-               /* IP6 */
-               ip6 = (struct ip6_hdr *)(eth+1);
-
-               /* we only want TCP */
-               if (ip6->ip6_nxt != IPPROTO_TCP) {
-                       return ENOMSG;
-               }
-
-               /* TCP */
-               tcp = (struct tcphdr *)(ip6+1);
-
-               /* tell the caller which one we've found */
-               src->ip6.sin6_family = AF_INET6;
-               src->ip6.sin6_port   = tcp->th_sport;
-               src->ip6.sin6_addr   = ip6->ip6_src;
-
-               dst->ip6.sin6_family = AF_INET6;
-               dst->ip6.sin6_port   = tcp->th_dport;
-               dst->ip6.sin6_addr   = ip6->ip6_dst;
-
-               *ack_seq             = tcp->th_ack;
-               *seq                 = tcp->th_seq;
-               if (window != NULL) {
-                       *window = tcp->th_win;
-               }
-               if (rst != NULL) {
-                       *rst = tcp->th_flags & TH_RST;
-               }
-
-               return 0;
+               ret = tcp6_extract(pkt + sizeof(struct ether_header),
+                                  (size_t)nread - sizeof(struct ether_header),
+                                  &src->ip6,
+                                  &dst->ip6,
+                                  ack_seq,
+                                  seq,
+                                  rst,
+                                  window);
+               return ret;
        }
 
        return ENOMSG;
@@ -923,9 +978,6 @@ int ctdb_sys_read_tcp_packet(int s,
 {
        int ret;
        struct ether_header *eth;
-       struct ip *ip;
-       struct ip6_hdr *ip6;
-       struct tcphdr *tcp;
        struct pcap_pkthdr pkthdr;
        const u_char *buffer;
        pcap_t *pt = (pcap_t *)private_data;
@@ -943,78 +995,28 @@ int ctdb_sys_read_tcp_packet(int s,
 
        /* we want either IPv4 or IPv6 */
        if (eth->ether_type == htons(ETHERTYPE_IP)) {
-               /* IP */
-               ip = (struct ip *)(eth+1);
-
-               /* We only want IPv4 packets */
-               if (ip->ip_v != 4) {
-                       return ENOMSG;
-               }
-               /* Dont look at fragments */
-               if ((ntohs(ip->ip_off)&0x1fff) != 0) {
-                       return ENOMSG;
-               }
-               /* we only want TCP */
-               if (ip->ip_p != IPPROTO_TCP) {
-                       return ENOMSG;
-               }
-
-               /* make sure its not a short packet */
-               if (offsetof(struct tcphdr, th_ack) + 4 +
-                   (ip->ip_hl*4) + sizeof(*eth) > pkthdr.caplen) {
-                       return EMSGSIZE;
-               }
-               /* TCP */
-               tcp = (struct tcphdr *)((ip->ip_hl*4) + (char *)ip);
-
-               /* tell the caller which one we've found */
-               src->ip.sin_family      = AF_INET;
-               src->ip.sin_addr.s_addr = ip->ip_src.s_addr;
-               src->ip.sin_port        = tcp->th_sport;
-               dst->ip.sin_family      = AF_INET;
-               dst->ip.sin_addr.s_addr = ip->ip_dst.s_addr;
-               dst->ip.sin_port        = tcp->th_dport;
-               *ack_seq                = tcp->th_ack;
-               *seq                    = tcp->th_seq;
-               if (window != NULL) {
-                       *window = tcp->th_win;
-               }
-               if (rst != NULL) {
-                       *rst = tcp->th_flags & TH_RST;
-               }
+               ret = tcp4_extract(buffer + sizeof(struct ether_header),
+                                  (size_t)(pkthdr.caplen -
+                                           sizeof(struct ether_header)),
+                                  &src->ip,
+                                  &dst->ip,
+                                  ack_seq,
+                                  seq,
+                                  rst,
+                                  window);
+               return ret;
 
-               return 0;
        } else if (eth->ether_type == htons(ETHERTYPE_IP6)) {
-                       /* IP6 */
-               ip6 = (struct ip6_hdr *)(eth+1);
-
-               /* we only want TCP */
-               if (ip6->ip6_nxt != IPPROTO_TCP) {
-                       return ENOMSG;
-               }
-
-               /* TCP */
-               tcp = (struct tcphdr *)(ip6+1);
-
-               /* tell the caller which one we've found */
-               src->ip6.sin6_family = AF_INET6;
-               src->ip6.sin6_port   = tcp->th_sport;
-               src->ip6.sin6_addr   = ip6->ip6_src;
-
-               dst->ip6.sin6_family = AF_INET6;
-               dst->ip6.sin6_port   = tcp->th_dport;
-               dst->ip6.sin6_addr   = ip6->ip6_dst;
-
-               *ack_seq             = tcp->th_ack;
-               *seq                 = tcp->th_seq;
-               if (window != NULL) {
-                       *window = tcp->th_win;
-               }
-               if (rst != NULL) {
-                       *rst = tcp->th_flags & TH_RST;
-               }
-
-               return 0;
+               ret = tcp6_extract(buffer + sizeof(struct ether_header),
+                                  (size_t)(pkthdr.caplen -
+                                           sizeof(struct ether_header)),
+                                  &src->ip6,
+                                  &dst->ip6,
+                                  ack_seq,
+                                  seq,
+                                  rst,
+                                  window);
+               return ret;
        }
 
        return ENOMSG;