diff --git a/bpf.c b/bpf.c index 87ff51b5..fac1063b 100644 --- a/bpf.c +++ b/bpf.c @@ -47,33 +47,33 @@ static char copyright[] = #include "dhcpd.h" #include +#include #include -#include -#include #include #include #include #include #include +#if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) /* Called by get_interface_list for each interface that's discovered. Opens a packet filter for each interface and adds it to the select mask. */ -void if_register (info, ifp) - struct interface_info *addr; +int if_register_bpf (info, ifp) + struct interface_info *info; struct ifreq *ifp; { - int b; + int sock; char filename[50]; - struct sockaddr_in sock; + int b; /* Open a BPF device */ for (b = 0; 1; b++) { snprintf(filename, sizeof(filename), "/dev/bpf%d", b); - info -> wfdesc = .bpf = open(filename, O_RDWR, 0); - if (info -> rfdesc < 0) { + sock = open (filename, O_RDWR, 0); + if (sock < 0) { if (errno == EBUSY) { continue; } else { @@ -85,7 +85,261 @@ void if_register (info, ifp) } /* Set the BPF device to point at this interface. */ - if (ioctl(info -> rfdesc, BIOCSETIF, ifp) < 0) - error ("Can't BIOCSETIF on bpf: %m"); -} + if (ioctl (sock, BIOCSETIF, ifp) < 0) + error ("Can't attach interface to bpf device: %m"); + return sock; +} +#endif /* USE_BPF_SEND || USE_BPF_RECEIVE */ + +#ifdef USE_BPF_SEND +void if_register_send (info, interface) + struct interface_info *info; + struct ifreq *interface; +{ + /* If we're using the bpf API for sending and receiving, + we don't need to register this interface twice. */ +#ifndef USE_BPF_RECEIVE + info -> wfdesc = if_register_bpf (info, interface); +#else + info -> wfdesc = info -> rfdesc; +#endif + note ("Sending on %s", piaddr (info -> address)); +} +#endif /* USE_BPF_SEND */ + +#ifdef USE_BPF_RECEIVE +/* Packet filter program... + XXX Changes to the filter program may require changes to the constant + offsets used in if_register_send to patch the BPF program! XXX */ + +struct bpf_insn filter [] = { + /* Make sure this is an IP packet... */ + BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12), + BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 12), + + /* Make sure it's a UDP packet... */ + BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23), + BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 10), + + /* Make sure this isn't a fragment... */ + BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), + BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 8, 0), + + /* Get the IP header length... */ + BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14), + + /* Make sure it's to the right port... */ + BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16), + BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 5), /* patch */ + + /* Is it to the broadcast address? */ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 30), + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xffffffff, 2, 0), + + /* If not, is it to our address? */ + + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 30), + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xffffffff, 0, 1), /* patch */ + + /* If we passed all the tests, ask for the whole packet. */ + BPF_STMT(BPF_RET+BPF_K, (u_int)-1), + + /* Otherwise, drop it. */ + BPF_STMT(BPF_RET+BPF_K, 0), +}; + +void if_register_receive (info, interface) + struct interface_info *info; + struct ifreq *interface; +{ + int flag = 1; + struct bpf_version v; + u_int32_t addr; + struct bpf_program p; + + /* Open a BPF device and hang it on this interface... */ + info -> rfdesc = if_register_bpf (info, interface); + + /* Make sure the BPF version is in range... */ + if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0) + error ("Can't get BPF version: %m"); + + if (v.bv_major != BPF_MAJOR_VERSION || + v.bv_minor < BPF_MINOR_VERSION) + error ("Kernel BPF version out of range - recompile dhcpd!"); + + /* Set immediate mode so that reads return as soon as a packet + comes in, rather than waiting for the input buffer to fill with + packets. */ + if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0) + error ("Can't set immediate mode on bpf device: %m"); + + /* Get the required BPF buffer length from the kernel. */ + if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0) + error ("Can't get bpf buffer length: %m"); + info -> rbuf = malloc (info -> rbuf_max); + if (!info -> rbuf) + error ("Can't allocate %d bytes for bpf input buffer."); + info -> rbuf_offset = 0; + info -> rbuf_len = 0; + + /* Patch the server port and interface address into the BPF + program... XXX changes to filter program may require changes + to the insn numbers used below! XXX */ + filter [8].k = ntohs (server_port); + memcpy (&addr, info -> address.iabuf, 4); + filter [12].k = ntohl (addr); + + /* Set up the bpf filter program structure. */ + p.bf_len = sizeof filter / sizeof (struct bpf_insn); + p.bf_insns = filter; + + if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0) + error ("Can't install packet filter program: %m"); + note ("Listening on %s", piaddr (info -> address)); +} +#endif /* USE_BPF_RECEIVE */ + +#ifdef USE_BPF_SEND +size_t send_packet (interface, packet, raw, len, to, hto) + struct interface_info *interface; + struct packet *packet; + struct dhcp_packet *raw; + size_t len; + struct sockaddr_in *to; + struct hardware *hto; +{ + int bufp = 0; + unsigned char buf [256]; + struct iovec iov [2]; + + /* Assemble the headers... */ + assemble_hw_header (interface, buf, &bufp, hto); + assemble_udp_ip_header (interface, buf, &bufp, + to -> sin_addr.s_addr, to -> sin_port, + (unsigned char *)raw, len); + + /* Fire it off */ + iov [0].iov_base = buf; + iov [0].iov_len = bufp; + iov [1].iov_base = (char *)raw; + iov [1].iov_len = len; + + return writev(interface -> wfdesc, iov, 2); +} +#endif /* USE_BPF_SEND */ + +#ifdef USE_BPF_RECEIVE +size_t receive_packet (interface, buf, len, from, hfrom) + struct interface_info *interface; + unsigned char *buf; + size_t len; + struct sockaddr_in *from; + struct hardware *hfrom; +{ + int length = 0; + int offset = 0; + struct bpf_hdr hdr; + + /* All this complexity is because BPF doesn't guarantee + that only one packet will be returned at a time. We're + getting what we deserve, though - this is a terrible abuse + of the BPF interface. Sigh. */ + + /* Process packets until we get one we can return or until we've + done a read and gotten nothing we can return... */ + + do { + /* If the buffer is empty, fill it. */ + if (interface -> rbuf_offset == interface -> rbuf_len) { + length = read (interface -> rfdesc, + interface -> rbuf, + interface -> rbuf_max); + if (length <= 0) + return length; + interface -> rbuf_offset = 0; + interface -> rbuf_len = length; + } + + /* If there isn't room for a whole bpf header, something went + wrong, but we'll ignore it and hope it goes away... XXX */ + if (interface -> rbuf_len - + interface -> rbuf_offset < sizeof hdr) { + interface -> rbuf_offset = interface -> rbuf_len; + continue; + } + + /* Copy out a bpf header... */ + memcpy (&hdr, &interface -> rbuf [interface -> rbuf_offset], + sizeof hdr); + + /* If the bpf header plus data doesn't fit in what's left + of the buffer, stick head in sand yet again... */ + if (interface -> rbuf_offset + + hdr.bh_hdrlen + hdr.bh_caplen > interface -> rbuf_len) { + interface -> rbuf_offset = interface -> rbuf_len; + continue; + } + + /* If the captured data wasn't the whole packet, or if + the packet won't fit in the input buffer, all we + can do is drop it. */ + if (hdr.bh_caplen != hdr.bh_datalen) { + interface -> rbuf_offset += + hdr.bh_hdrlen = hdr.bh_caplen; + continue; + } + + /* Skip over the BPF header... */ + interface -> rbuf_offset += hdr.bh_hdrlen; + + /* Decode the physical header... */ + offset = decode_hw_header (interface, + interface -> rbuf, + interface -> rbuf_offset, + hfrom); + + /* If a physical layer checksum failed (dunno of any + physical layer that supports this, but WTH), skip this + packet. */ + if (offset < 0) { + interface -> rbuf_offset += hdr.bh_caplen; + continue; + } + interface -> rbuf_offset += offset; + hdr.bh_caplen -= offset; + + /* Decode the IP and UDP headers... */ + offset = decode_udp_ip_header (interface, + interface -> rbuf, + interface -> rbuf_offset, + from, + (unsigned char *)0, + hdr.bh_caplen); + + /* If the IP or UDP checksum was bad, skip the packet... */ + if (offset < 0) { + interface -> rbuf_offset += hdr.bh_caplen; + continue; + } + interface -> rbuf_offset += offset; + hdr.bh_caplen -= offset; + + /* If there's not enough room to stash the packet data, + we have to skip it (this shouldn't happen in real + life, though). */ + if (hdr.bh_caplen > len) { + interface -> rbuf_offset += hdr.bh_caplen; + continue; + } + + /* Copy out the data in the packet... */ + memcpy (buf, interface -> rbuf + interface -> rbuf_offset, + hdr.bh_caplen); + interface -> rbuf_offset += hdr.bh_caplen; + return hdr.bh_caplen; + } while (!length); + return 0; +} +#endif diff --git a/common/bpf.c b/common/bpf.c index 87ff51b5..fac1063b 100644 --- a/common/bpf.c +++ b/common/bpf.c @@ -47,33 +47,33 @@ static char copyright[] = #include "dhcpd.h" #include +#include #include -#include -#include #include #include #include #include #include +#if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) /* Called by get_interface_list for each interface that's discovered. Opens a packet filter for each interface and adds it to the select mask. */ -void if_register (info, ifp) - struct interface_info *addr; +int if_register_bpf (info, ifp) + struct interface_info *info; struct ifreq *ifp; { - int b; + int sock; char filename[50]; - struct sockaddr_in sock; + int b; /* Open a BPF device */ for (b = 0; 1; b++) { snprintf(filename, sizeof(filename), "/dev/bpf%d", b); - info -> wfdesc = .bpf = open(filename, O_RDWR, 0); - if (info -> rfdesc < 0) { + sock = open (filename, O_RDWR, 0); + if (sock < 0) { if (errno == EBUSY) { continue; } else { @@ -85,7 +85,261 @@ void if_register (info, ifp) } /* Set the BPF device to point at this interface. */ - if (ioctl(info -> rfdesc, BIOCSETIF, ifp) < 0) - error ("Can't BIOCSETIF on bpf: %m"); -} + if (ioctl (sock, BIOCSETIF, ifp) < 0) + error ("Can't attach interface to bpf device: %m"); + return sock; +} +#endif /* USE_BPF_SEND || USE_BPF_RECEIVE */ + +#ifdef USE_BPF_SEND +void if_register_send (info, interface) + struct interface_info *info; + struct ifreq *interface; +{ + /* If we're using the bpf API for sending and receiving, + we don't need to register this interface twice. */ +#ifndef USE_BPF_RECEIVE + info -> wfdesc = if_register_bpf (info, interface); +#else + info -> wfdesc = info -> rfdesc; +#endif + note ("Sending on %s", piaddr (info -> address)); +} +#endif /* USE_BPF_SEND */ + +#ifdef USE_BPF_RECEIVE +/* Packet filter program... + XXX Changes to the filter program may require changes to the constant + offsets used in if_register_send to patch the BPF program! XXX */ + +struct bpf_insn filter [] = { + /* Make sure this is an IP packet... */ + BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12), + BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 12), + + /* Make sure it's a UDP packet... */ + BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23), + BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 10), + + /* Make sure this isn't a fragment... */ + BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20), + BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 8, 0), + + /* Get the IP header length... */ + BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14), + + /* Make sure it's to the right port... */ + BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16), + BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 5), /* patch */ + + /* Is it to the broadcast address? */ + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 30), + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xffffffff, 2, 0), + + /* If not, is it to our address? */ + + BPF_STMT(BPF_LD+BPF_W+BPF_ABS, 30), + BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xffffffff, 0, 1), /* patch */ + + /* If we passed all the tests, ask for the whole packet. */ + BPF_STMT(BPF_RET+BPF_K, (u_int)-1), + + /* Otherwise, drop it. */ + BPF_STMT(BPF_RET+BPF_K, 0), +}; + +void if_register_receive (info, interface) + struct interface_info *info; + struct ifreq *interface; +{ + int flag = 1; + struct bpf_version v; + u_int32_t addr; + struct bpf_program p; + + /* Open a BPF device and hang it on this interface... */ + info -> rfdesc = if_register_bpf (info, interface); + + /* Make sure the BPF version is in range... */ + if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0) + error ("Can't get BPF version: %m"); + + if (v.bv_major != BPF_MAJOR_VERSION || + v.bv_minor < BPF_MINOR_VERSION) + error ("Kernel BPF version out of range - recompile dhcpd!"); + + /* Set immediate mode so that reads return as soon as a packet + comes in, rather than waiting for the input buffer to fill with + packets. */ + if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0) + error ("Can't set immediate mode on bpf device: %m"); + + /* Get the required BPF buffer length from the kernel. */ + if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0) + error ("Can't get bpf buffer length: %m"); + info -> rbuf = malloc (info -> rbuf_max); + if (!info -> rbuf) + error ("Can't allocate %d bytes for bpf input buffer."); + info -> rbuf_offset = 0; + info -> rbuf_len = 0; + + /* Patch the server port and interface address into the BPF + program... XXX changes to filter program may require changes + to the insn numbers used below! XXX */ + filter [8].k = ntohs (server_port); + memcpy (&addr, info -> address.iabuf, 4); + filter [12].k = ntohl (addr); + + /* Set up the bpf filter program structure. */ + p.bf_len = sizeof filter / sizeof (struct bpf_insn); + p.bf_insns = filter; + + if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0) + error ("Can't install packet filter program: %m"); + note ("Listening on %s", piaddr (info -> address)); +} +#endif /* USE_BPF_RECEIVE */ + +#ifdef USE_BPF_SEND +size_t send_packet (interface, packet, raw, len, to, hto) + struct interface_info *interface; + struct packet *packet; + struct dhcp_packet *raw; + size_t len; + struct sockaddr_in *to; + struct hardware *hto; +{ + int bufp = 0; + unsigned char buf [256]; + struct iovec iov [2]; + + /* Assemble the headers... */ + assemble_hw_header (interface, buf, &bufp, hto); + assemble_udp_ip_header (interface, buf, &bufp, + to -> sin_addr.s_addr, to -> sin_port, + (unsigned char *)raw, len); + + /* Fire it off */ + iov [0].iov_base = buf; + iov [0].iov_len = bufp; + iov [1].iov_base = (char *)raw; + iov [1].iov_len = len; + + return writev(interface -> wfdesc, iov, 2); +} +#endif /* USE_BPF_SEND */ + +#ifdef USE_BPF_RECEIVE +size_t receive_packet (interface, buf, len, from, hfrom) + struct interface_info *interface; + unsigned char *buf; + size_t len; + struct sockaddr_in *from; + struct hardware *hfrom; +{ + int length = 0; + int offset = 0; + struct bpf_hdr hdr; + + /* All this complexity is because BPF doesn't guarantee + that only one packet will be returned at a time. We're + getting what we deserve, though - this is a terrible abuse + of the BPF interface. Sigh. */ + + /* Process packets until we get one we can return or until we've + done a read and gotten nothing we can return... */ + + do { + /* If the buffer is empty, fill it. */ + if (interface -> rbuf_offset == interface -> rbuf_len) { + length = read (interface -> rfdesc, + interface -> rbuf, + interface -> rbuf_max); + if (length <= 0) + return length; + interface -> rbuf_offset = 0; + interface -> rbuf_len = length; + } + + /* If there isn't room for a whole bpf header, something went + wrong, but we'll ignore it and hope it goes away... XXX */ + if (interface -> rbuf_len - + interface -> rbuf_offset < sizeof hdr) { + interface -> rbuf_offset = interface -> rbuf_len; + continue; + } + + /* Copy out a bpf header... */ + memcpy (&hdr, &interface -> rbuf [interface -> rbuf_offset], + sizeof hdr); + + /* If the bpf header plus data doesn't fit in what's left + of the buffer, stick head in sand yet again... */ + if (interface -> rbuf_offset + + hdr.bh_hdrlen + hdr.bh_caplen > interface -> rbuf_len) { + interface -> rbuf_offset = interface -> rbuf_len; + continue; + } + + /* If the captured data wasn't the whole packet, or if + the packet won't fit in the input buffer, all we + can do is drop it. */ + if (hdr.bh_caplen != hdr.bh_datalen) { + interface -> rbuf_offset += + hdr.bh_hdrlen = hdr.bh_caplen; + continue; + } + + /* Skip over the BPF header... */ + interface -> rbuf_offset += hdr.bh_hdrlen; + + /* Decode the physical header... */ + offset = decode_hw_header (interface, + interface -> rbuf, + interface -> rbuf_offset, + hfrom); + + /* If a physical layer checksum failed (dunno of any + physical layer that supports this, but WTH), skip this + packet. */ + if (offset < 0) { + interface -> rbuf_offset += hdr.bh_caplen; + continue; + } + interface -> rbuf_offset += offset; + hdr.bh_caplen -= offset; + + /* Decode the IP and UDP headers... */ + offset = decode_udp_ip_header (interface, + interface -> rbuf, + interface -> rbuf_offset, + from, + (unsigned char *)0, + hdr.bh_caplen); + + /* If the IP or UDP checksum was bad, skip the packet... */ + if (offset < 0) { + interface -> rbuf_offset += hdr.bh_caplen; + continue; + } + interface -> rbuf_offset += offset; + hdr.bh_caplen -= offset; + + /* If there's not enough room to stash the packet data, + we have to skip it (this shouldn't happen in real + life, though). */ + if (hdr.bh_caplen > len) { + interface -> rbuf_offset += hdr.bh_caplen; + continue; + } + + /* Copy out the data in the packet... */ + memcpy (buf, interface -> rbuf + interface -> rbuf_offset, + hdr.bh_caplen); + interface -> rbuf_offset += hdr.bh_caplen; + return hdr.bh_caplen; + } while (!length); + return 0; +} +#endif